Bitcoin Wiki - User contributions [en]

Controlled supply

2016-05-03T06:07:33Z

Atheros: Looks like Wikipedia changed the capitalization of their article. To answer questions, also see this Bitcoin wiki article: https://en.bitcoin.it/wiki/Fractional_Reserve_Banking_and_Bitcoin

<blockquote>A fixed money supply, or a supply altered only in accord with objective and calculable criteria, is a necessary condition to a meaningful just price of money.<ref>[https://www.scribd.com/doc/138347161/Bernard-W-Dempsey-1903-1960-Interest-and-Usury-With-an-Introduction-by-Joseph-a-Schumpeter-1948#page220 Interest and Usury p. 220] by [https://www.jstor.org/stable/29769582 Fr. Bernard W. Dempsey, S.J.] (1903-1960); cf. John Horvat II [http://returntoorder.org/ Return to Order] ch. 37 "The Backing of Money"</ref>
—[https://www.jstor.org/stable/29769582 Fr. Bernard W. Dempsey, S.J.] (1903-1960)</blockquote>

In a centralized economy, currency is issued by a central bank at a rate that is supposed to match the growth of the amount of goods that are exchanged so that these goods can be traded with stable prices. The
[[wikipedia:monetary base|monetary base]] is controlled by a central bank. In the United States, the [[wikipedia:Federal Reserve System|Fed]] increases the monetary base by issuing currency, increasing the amount banks have on reserve, and more recently, printing money electronically in a process called [[wikipedia:Quantitative Easing|Quantitative Easing]].

In a fully decentralized monetary system, there is no central authority that regulates the monetary base. Instead, currency is created by the nodes of a peer-to-peer network. The Bitcoin generation algorithm defines, in advance, how currency will be created and at what rate. Any currency that is generated by a malicious user that does not follow the rules will be rejected by the network and thus is worthless.

==Currency with Finite Supply==
[[Image:Controlled supply-block reward halving.png|160px|thumb|right| Block reward halving]]
[[Image:Controlled supply-supply over block height.png|160px|thumb|right| Controlled supply]]
Bitcoins are created each time a user discovers a new [[block]].
The rate of block creation is adjusted every 2016 blocks to aim for a constant two week adjustment period (equivalent to 6 per hour.) The number of bitcoins generated per block is set to decrease geometrically, with a 50% reduction every 210,000 blocks, or approximately four years. The result is that the number of bitcoins in existence is not expected to exceed 21 million.<ref>[http://www.bitcointalk.org/index.php?topic=3366.msg47522#msg47522 21 million cap]</ref> Speculated justifications for the unintuitive value "21 million" are that it matches a 4-year reward halving schedule; or the ultimate total number of Satoshis that will be mined is close to the maximum capacity of a 64-bit floating point number. Satoshi has never really justified or explained many of these constants.

[[File:ControlledSupply.png]]

This decreasing-supply algorithm was chosen because it approximates the rate at which commodities like gold are mined. Users who use their computers to perform calculations to try and discover a block are thus called [[Mining|''Miners'']].

==Projected Bitcoins Short Term ==
This chart shows the number of bitcoins that will exist in the near future. The ''Year'' is a forecast and may be slightly off.
{| class="wikitable"
|-
! Date reached!!Block!!Reward Era!! BTC/block!! Year (estimate)!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
|2009-01-03||0||1||50.00||2009||0||2625000||2625000||infinite||12.500%
|-
|2010-04-22||52500||1||50.00||2010||2625000||2625000||5250000||100.00%||25.000%
|-
|2011-01-28||105000||1||50.00||2011*||5250000||2625000||7875000||50.00%||37.500%
|-
|2011-12-14||157500||1||50.00||2012||7875000||2625000||10500000||33.33%||50.000%
|-
|[[Halving day 2012|2012-11-28]]||210000||2||25.00||2013||10500000||1312500||11812500||12.50%||56.250%
|-
|2013-10-09||262500||2||25.00||2014||11812500||1312500||13125000||11.11%||62.500%
|-
|2014-08-11||315000||2||25.00||2015||13125000||1312500||14437500||10.00%||68.750%
|-
|2015-07-29||367500||2||25.00||2016||14437500||1312500||15750000||9.09%||75.000%
|-
|||420000||3||12.50||2017||15750000||656250||16406250||4.17%||78.125%
|-
|||472500||3||12.50||2018||16406250||656250||17062500||4.00%||81.250%
|-
|||525000||3||12.50||2019||17062500||656250||17718750||3.85%||84.375%
|-
|||577500||3||12.50||2020||17718750||656250||18375000||3.70%||87.500%
|-
|||630000||4||6.25||2021||18375000||328125||18703125||1.79%||89.063%
|-
|||682500||4||6.25||2022||18703125||328125||19031250||1.75%||90.625%
|-
|||735000||4||6.25||2023||19031250||328125||19359375||1.72%||92.188%
|-
|||787500||4||6.25||2024||19359375||328125||19687500||1.69%||93.750%
|}
''* In Block 124724, user midnightmagic mined a solo block to himself which underpaid the reward by a single Satoshi and simultaneously destroyed the block's fees. This the the only known reduction in the total mined supply of Bitcoin. Therefore, from block 124724 onwards, all total supply estimates must technically be reduced by 1 Satoshi.

==Projected Bitcoins Long Term ==
[[Image:Controlled supply-timeline estimation.png|160px|thumb|right| Supply timeline estimation]]
Because the number of bitcoins created each time a user discovers a new block - the block reward - is halved based on a fixed interval of blocks, and the time it takes on average to discover a block can vary based on [[mining]] power and the network [[difficulty]], the exact time when the block reward is halved can vary as well. Consequently, the time the last Bitcoin will be created will also vary, and is subject to speculation based on assumptions.

If the mining power had remained constant since the first Bitcoin was mined, the last Bitcoin would have been mined somewhere near October 8th, 2140. Due to the mining power having increased overall over time, as of block 367,500 - assuming mining power remained constant from that block forward - the last Bitcoin will be mined on May 7th, 2140.

As it is very difficult to predict how mining power will evolve into the future - i.e. whether technological progress will continue to make hardware faster or whether mining will hit a a technological wall; or whether or not faster methods of SHA2 calculation will be discovered - putting an exact date or even year on this event is difficult.

The total number of bitcoins, as mentioned earlier, has an asymptote at 21 million, due to a technical limitation in the data structure of the blockchain - specifically the integer storage type of the [[Transaction#general_format_.28inside_a_block.29_of_each_output_of_a_transaction_-_Txout|transaction output]], this exact value would have been 20,999,999.9769 bitcoin. Should this technical limitation be adjusted by changing the width of the field, the total number will still only approach or be a maximum of 21 million.

{| class="wikitable" style="text-align:right"
|-
! Block!!Reward Era!! BTC/block!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
| 0|| 1|| 50.00000000|| 0.00000000|| 10500000.00000000|| 10500000.00000000*|| infinite|| 50.00000006%
|-
| 210000|| 2|| 25.00000000|| 10500000.00000000|| 5250000.00000000|| 15750000.00000000|| 50.00000000%|| 75.00000008%
|-
| 420000|| 3|| 12.50000000|| 15750000.00000000|| 2625000.00000000|| 18375000.00000000|| 16.66666667%|| 87.50000010%
|-
| 630000|| 4|| 6.25000000|| 18375000.00000000|| 1312500.00000000|| 19687500.00000000|| 7.14285714%|| 93.75000010%
|-
| 840000|| 5|| 3.12500000|| 19687500.00000000|| 656250.00000000|| 20343750.00000000|| 3.33333333%|| 96.87500011%
|-
| 1050000|| 6|| 1.56250000|| 20343750.00000000|| 328125.00000000|| 20671875.00000000|| 1.61290323%|| 98.43750011%
|-
| 1260000|| 7|| 0.78125000|| 20671875.00000000|| 164062.50000000|| 20835937.50000000|| 0.79365079%|| 99.21875011%
|-
| 1470000|| 8|| 0.39062500|| 20835937.50000000|| 82031.25000000|| 20917968.75000000|| 0.39370079%|| 99.60937511%
|-
| 1680000|| 9|| 0.19531250|| 20917968.75000000|| 41015.62500000|| 20958984.37500000|| 0.19607843%|| 99.80468761%
|-
| 1890000|| 10|| 0.09765625|| 20958984.37500000|| 20507.81250000|| 20979492.18750000|| 0.09784736%|| 99.90234386%
|-
| 2100000|| 11|| 0.04882812|| 20979492.18750000|| 10253.90520000|| 20989746.09270000|| 0.04887585%|| 99.95117198%
|-
| 2310000|| 12|| 0.02441406|| 20989746.09270000|| 5126.95260000|| 20994873.04530000|| 0.02442599%|| 99.97558604%
|-
| 2520000|| 13|| 0.01220703|| 20994873.04530000|| 2563.47630000|| 20997436.52160000|| 0.01221001%|| 99.98779307%
|-
| 2730000|| 14|| 0.00610351|| 20997436.52160000|| 1281.73710000|| 20998718.25870000|| 0.00610426%|| 99.99389658%
|-
| 2940000|| 15|| 0.00305175|| 20998718.25870000|| 640.86750000|| 20999359.12620000|| 0.00305194%|| 99.99694833%
|-
| 3150000|| 16|| 0.00152587|| 20999359.12620000|| 320.43270000|| 20999679.55890000|| 0.00152592%|| 99.99847420%
|-
| 3360000|| 17|| 0.00076293|| 20999679.55890000|| 160.21530000|| 20999839.77420000|| 0.00076294%|| 99.99923713%
|-
| 3570000|| 18|| 0.00038146|| 20999839.77420000|| 80.10660000|| 20999919.88080000|| 0.00038146%|| 99.99961859%
|-
| 3780000|| 19|| 0.00019073|| 20999919.88080000|| 40.05330000|| 20999959.93410000|| 0.00019073%|| 99.99980932%
|-
| 3990000|| 20|| 0.00009536|| 20999959.93410000|| 20.02560000|| 20999979.95970000|| 0.00009536%|| 99.99990468%
|-
| 4200000|| 21|| 0.00004768|| 20999979.95970000|| 10.01280000|| 20999989.97250000|| 0.00004768%|| 99.99995236%
|-
| 4410000|| 22|| 0.00002384|| 20999989.97250000|| 5.00640000|| 20999994.97890000|| 0.00002384%|| 99.99997620%
|-
| 4620000|| 23|| 0.00001192|| 20999994.97890000|| 2.50320000|| 20999997.48210000|| 0.00001192%|| 99.99998812%
|-
| 4830000|| 24|| 0.00000596|| 20999997.48210000|| 1.25160000|| 20999998.73370000|| 0.00000596%|| 99.99999408%
|-
| 5040000|| 25|| 0.00000298|| 20999998.73370000|| 0.62580000|| 20999999.35950000|| 0.00000298%|| 99.99999706%
|-
| 5250000|| 26|| 0.00000149|| 20999999.35950000|| 0.31290000|| 20999999.67240000|| 0.00000149%|| 99.99999855%
|-
| 5460000|| 27|| 0.00000074|| 20999999.67240000|| 0.15540000|| 20999999.82780000|| 0.00000074%|| 99.99999929%
|-
| 5670000|| 28|| 0.00000037|| 20999999.82780000|| 0.07770000|| 20999999.90550000|| 0.00000037%|| 99.99999966%
|-
| 5880000|| 29|| 0.00000018|| 20999999.90550000|| 0.03780000|| 20999999.94330000|| 0.00000018%|| 99.99999984%
|-
| 6090000|| 30|| 0.00000009|| 20999999.94330000|| 0.01890000|| 20999999.96220000|| 0.00000009%|| 99.99999993%
|-
| 6300000|| 31|| 0.00000004|| 20999999.96220000|| 0.00840000|| 20999999.97060000|| 0.00000004%|| 99.99999997%
|-
| 6510000|| 32|| 0.00000002|| 20999999.97060000|| 0.00420000|| 20999999.97480000|| 0.00000002%|| 99.99999999%
|-
| 6720000|| 33|| 0.00000001|| 20999999.97480000|| 0.00210000|| 20999999.97690000|| 0.00000001%|| 100.00000000%
|-
| 6930000|| 34|| 0.00000000|| 20999999.97690000|| 0.00000000|| 20999999.97690000|| 0.00000000%|| 100.00000000%
|}
''Note: The number of bitcoins are presented in a floating point format. However, these values are based on the number of satoshi per block originally in integer format to prevent compounding error.''

''* In block 124724, user midnightmagic solo mined a block which caused one less Satoshi to be created than would otherwise have come into existence. Therefore, all calculations from this block onwards must now, to be accurate, include this underpay in total Bitcoins in existence.''

==Spendable Supply==
The theoretical total number of bitcoins, 21 million, should not be confused with the total spendable supply. The total spendable supply is always lower than the theoretical total supply, and is subject to accidental loss, willful destruction, and technical peculiarities.

One way to see a part of the destruction of coin is by collecting a sum of all unspent transaction outputs, using a [[API reference (JSON-RPC)|Bitcoin RPC]] command <code>gettxoutsetinfo</code>. The ''total_amount'' value returned is the sum of all outputs that the client deems technically spendable but not currently spent. Note however that this does not take into account outputs that are exceedingly unlikely to be spent as is the case in loss and destruction via constructed addresses, for example.
===Miner Underpay===

The algorithm which decides whether a block is valid only checks to verify whether the total amount of the reward '''exceeds''' the reward plus available fees. Therefore it is possible for a miner to deliberately choose to underpay himself by any value: not only can this destroy the fees involved, but also the reward itself, which can prevent the total possible bitcoins that can come into existence from reaching its theoretical meximum. This is a form of underpay which the reference implementation recognises as impossible to spend. Some of the other types below are not recognised as officially destroying Bitcoins; it is possible for example to spend the 1BitcoinEaterAddressDontSendf59kuE if a corresponding private key is used (although this would imply that Bitcoin has been broken.)

===Loss of bitcoin===
Bitcoins may be lost if the conditions required to spend them are no longer known. For example, if you made a transaction to an [[address]] that requires a private key in order to spend those bitcoins further, had written that private key down on a piece of paper, but that piece of paper was lost. In this case, that bitcoin may also be considered lost, as the odds of randomly finding a matching private key are such that it is generally considered impossible.

===Willful destruction of bitcoin===
Bitcoins may also be willfully 'destroyed' - for example by attaching conditions that make it impossible to spend them.

A common method is to send bitcoin to an address that was constructed and only made to pass validity checks, but for which no private key is actually known. An example of such an address is "1BitcoinEaterAddressDontSendf59kuE", where the last "f59kuE" is text to make the preceding constructed text pass validation. Finding a matching private key is, again, generally considered impossible. For an example of how difficult this would be, see [[Vanitygen#Use_of_vanitygen_to_try_to_attack_addresses|Vanitygen]].

Another common method is to send bitcoin in a transaction where the conditions for spending are not just unfathomably unlikely, but literally impossible to meet. For example, a transaction that is made [[Script#Provably_Unspendable.2FPrunable_Outputs|provably unspendable using OP_RETURN]], or uses script operations that requires the user to prove that 1+1 equals 3.

A lesser known method is to send bitcoin to an address based on private key that is outside the [[Private_key#Range_of_valid_ECDSA_private_keys|range of valid ECDSA private keys]]. For example, the address 16QaFeudRUt8NYy2yzjm3BMvG4xBbAsBFM has a known matching private key of value 0 (zero), which is outside the valid range.

===Technical peculiarities preventing spending of bitcoin===
There are also technical peculiarities that prevent the spending of some bitcoin.

The first {{btc}}50, included in the [[genesis block]], cannot be spent as its transaction is not in the global database.

In older versions of the bitcoin reference code, a miner could make their coinbase transaction (block reward) have the exact same ID as used in a previous block<ref>https://github.com/bitcoin/bitcoin/issues/612</ref>. This effectively caused the previous block reward to become unspendable. Two known such cases<ref>{{cite tx|e3bf3d07d4b0375638d5f1db5255fe07ba2c4cb067cd81b84ee974b6585fb468|used in blocks 91722 and 91880}}</ref><ref>{{cite tx|d5d27987d2a3dfc724e359870c6644b40e497bdc0589a033220fe15429d88599|used in blocks 91812 and 91842</ref> are left as special cases in the code<ref>https://github.com/bitcoin/bitcoin/commit/ab91bf39b7c11e9c86bb2043c24f0f377f1cf514</ref> as part of [[BIP 0030]] changes that fixed this issue. These transactions were {{btc}}50 each.

==Money Supply==
While the number of bitcoins in existence will never exceed 21 million, the [[wikipedia:money supply|money supply]] of bitcoins can exceed 21 million due to [[wikipedia:Fractional-reserve banking|Fractional-reserve banking]].

==Deflation==

Because the monetary base of bitcoins cannot be expanded, the currency would be subject to severe deflation if it becomes widely used.
Keynesian economists argue that [[Deflationary spiral|deflation]] is bad for an economy because it incentivises individuals and businesses to save money rather than invest in businesses and create jobs. The [[wikipedia:Austrian school|Austrian school]] of thought counters this criticism, claiming that as deflation occurs in all stages of production, entrepreneurs who invest benefit from it. As a result, profit ratios tend to stay the same and only their magnitudes change. In other words, in a deflationary environment, goods and services decrease in price, but at the same time the cost for the production of these goods and services tend to decrease proportionally, effectively not affecting profits. Price deflation encourages an increase in hoarding — hence savings — which in turn tends to lower interest rates and increase the incentive for entrepreneurs to invest in projects of longer term.

==See also==

* [http://www.econlib.org/library/Columns/y2006/Friedmantranscript.html Milton Friedman interview], where he proposed to replace the central bank with a computer, and to fix the money supply growth at 4% annually
* [[Deflationary spiral]]
* [http://blockchain.info/charts/total-bitcoins Chart of total bitcoins in circulation]
* [[Inflation]]
* [[Prohibited changes]]

==References==
<references />

[[Category:Economics]]

Controlled supply

2016-05-03T06:02:52Z

Atheros: Through fractional reserve banking. Perhaps read about the definition of money supply and why it is useful.

<blockquote>A fixed money supply, or a supply altered only in accord with objective and calculable criteria, is a necessary condition to a meaningful just price of money.<ref>[https://www.scribd.com/doc/138347161/Bernard-W-Dempsey-1903-1960-Interest-and-Usury-With-an-Introduction-by-Joseph-a-Schumpeter-1948#page220 Interest and Usury p. 220] by [https://www.jstor.org/stable/29769582 Fr. Bernard W. Dempsey, S.J.] (1903-1960); cf. John Horvat II [http://returntoorder.org/ Return to Order] ch. 37 "The Backing of Money"</ref>
—[https://www.jstor.org/stable/29769582 Fr. Bernard W. Dempsey, S.J.] (1903-1960)</blockquote>

In a centralized economy, currency is issued by a central bank at a rate that is supposed to match the growth of the amount of goods that are exchanged so that these goods can be traded with stable prices. The
[[wikipedia:monetary base|monetary base]] is controlled by a central bank. In the United States, the [[wikipedia:Federal Reserve System|Fed]] increases the monetary base by issuing currency, increasing the amount banks have on reserve, and more recently, printing money electronically in a process called [[wikipedia:Quantitative Easing|Quantitative Easing]].

In a fully decentralized monetary system, there is no central authority that regulates the monetary base. Instead, currency is created by the nodes of a peer-to-peer network. The Bitcoin generation algorithm defines, in advance, how currency will be created and at what rate. Any currency that is generated by a malicious user that does not follow the rules will be rejected by the network and thus is worthless.

==Currency with Finite Supply==
[[Image:Controlled supply-block reward halving.png|160px|thumb|right| Block reward halving]]
[[Image:Controlled supply-supply over block height.png|160px|thumb|right| Controlled supply]]
Bitcoins are created each time a user discovers a new [[block]].
The rate of block creation is adjusted every 2016 blocks to aim for a constant two week adjustment period (equivalent to 6 per hour.) The number of bitcoins generated per block is set to decrease geometrically, with a 50% reduction every 210,000 blocks, or approximately four years. The result is that the number of bitcoins in existence is not expected to exceed 21 million.<ref>[http://www.bitcointalk.org/index.php?topic=3366.msg47522#msg47522 21 million cap]</ref> Speculated justifications for the unintuitive value "21 million" are that it matches a 4-year reward halving schedule; or the ultimate total number of Satoshis that will be mined is close to the maximum capacity of a 64-bit floating point number. Satoshi has never really justified or explained many of these constants.

[[File:ControlledSupply.png]]

This decreasing-supply algorithm was chosen because it approximates the rate at which commodities like gold are mined. Users who use their computers to perform calculations to try and discover a block are thus called [[Mining|''Miners'']].

==Projected Bitcoins Short Term ==
This chart shows the number of bitcoins that will exist in the near future. The ''Year'' is a forecast and may be slightly off.
{| class="wikitable"
|-
! Date reached!!Block!!Reward Era!! BTC/block!! Year (estimate)!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
|2009-01-03||0||1||50.00||2009||0||2625000||2625000||infinite||12.500%
|-
|2010-04-22||52500||1||50.00||2010||2625000||2625000||5250000||100.00%||25.000%
|-
|2011-01-28||105000||1||50.00||2011*||5250000||2625000||7875000||50.00%||37.500%
|-
|2011-12-14||157500||1||50.00||2012||7875000||2625000||10500000||33.33%||50.000%
|-
|[[Halving day 2012|2012-11-28]]||210000||2||25.00||2013||10500000||1312500||11812500||12.50%||56.250%
|-
|2013-10-09||262500||2||25.00||2014||11812500||1312500||13125000||11.11%||62.500%
|-
|2014-08-11||315000||2||25.00||2015||13125000||1312500||14437500||10.00%||68.750%
|-
|2015-07-29||367500||2||25.00||2016||14437500||1312500||15750000||9.09%||75.000%
|-
|||420000||3||12.50||2017||15750000||656250||16406250||4.17%||78.125%
|-
|||472500||3||12.50||2018||16406250||656250||17062500||4.00%||81.250%
|-
|||525000||3||12.50||2019||17062500||656250||17718750||3.85%||84.375%
|-
|||577500||3||12.50||2020||17718750||656250||18375000||3.70%||87.500%
|-
|||630000||4||6.25||2021||18375000||328125||18703125||1.79%||89.063%
|-
|||682500||4||6.25||2022||18703125||328125||19031250||1.75%||90.625%
|-
|||735000||4||6.25||2023||19031250||328125||19359375||1.72%||92.188%
|-
|||787500||4||6.25||2024||19359375||328125||19687500||1.69%||93.750%
|}
''* In Block 124724, user midnightmagic mined a solo block to himself which underpaid the reward by a single Satoshi and simultaneously destroyed the block's fees. This the the only known reduction in the total mined supply of Bitcoin. Therefore, from block 124724 onwards, all total supply estimates must technically be reduced by 1 Satoshi.

==Projected Bitcoins Long Term ==
[[Image:Controlled supply-timeline estimation.png|160px|thumb|right| Supply timeline estimation]]
Because the number of bitcoins created each time a user discovers a new block - the block reward - is halved based on a fixed interval of blocks, and the time it takes on average to discover a block can vary based on [[mining]] power and the network [[difficulty]], the exact time when the block reward is halved can vary as well. Consequently, the time the last Bitcoin will be created will also vary, and is subject to speculation based on assumptions.

If the mining power had remained constant since the first Bitcoin was mined, the last Bitcoin would have been mined somewhere near October 8th, 2140. Due to the mining power having increased overall over time, as of block 367,500 - assuming mining power remained constant from that block forward - the last Bitcoin will be mined on May 7th, 2140.

As it is very difficult to predict how mining power will evolve into the future - i.e. whether technological progress will continue to make hardware faster or whether mining will hit a a technological wall; or whether or not faster methods of SHA2 calculation will be discovered - putting an exact date or even year on this event is difficult.

The total number of bitcoins, as mentioned earlier, has an asymptote at 21 million, due to a technical limitation in the data structure of the blockchain - specifically the integer storage type of the [[Transaction#general_format_.28inside_a_block.29_of_each_output_of_a_transaction_-_Txout|transaction output]], this exact value would have been 20,999,999.9769 bitcoin. Should this technical limitation be adjusted by changing the width of the field, the total number will still only approach or be a maximum of 21 million.

{| class="wikitable" style="text-align:right"
|-
! Block!!Reward Era!! BTC/block!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
| 0|| 1|| 50.00000000|| 0.00000000|| 10500000.00000000|| 10500000.00000000*|| infinite|| 50.00000006%
|-
| 210000|| 2|| 25.00000000|| 10500000.00000000|| 5250000.00000000|| 15750000.00000000|| 50.00000000%|| 75.00000008%
|-
| 420000|| 3|| 12.50000000|| 15750000.00000000|| 2625000.00000000|| 18375000.00000000|| 16.66666667%|| 87.50000010%
|-
| 630000|| 4|| 6.25000000|| 18375000.00000000|| 1312500.00000000|| 19687500.00000000|| 7.14285714%|| 93.75000010%
|-
| 840000|| 5|| 3.12500000|| 19687500.00000000|| 656250.00000000|| 20343750.00000000|| 3.33333333%|| 96.87500011%
|-
| 1050000|| 6|| 1.56250000|| 20343750.00000000|| 328125.00000000|| 20671875.00000000|| 1.61290323%|| 98.43750011%
|-
| 1260000|| 7|| 0.78125000|| 20671875.00000000|| 164062.50000000|| 20835937.50000000|| 0.79365079%|| 99.21875011%
|-
| 1470000|| 8|| 0.39062500|| 20835937.50000000|| 82031.25000000|| 20917968.75000000|| 0.39370079%|| 99.60937511%
|-
| 1680000|| 9|| 0.19531250|| 20917968.75000000|| 41015.62500000|| 20958984.37500000|| 0.19607843%|| 99.80468761%
|-
| 1890000|| 10|| 0.09765625|| 20958984.37500000|| 20507.81250000|| 20979492.18750000|| 0.09784736%|| 99.90234386%
|-
| 2100000|| 11|| 0.04882812|| 20979492.18750000|| 10253.90520000|| 20989746.09270000|| 0.04887585%|| 99.95117198%
|-
| 2310000|| 12|| 0.02441406|| 20989746.09270000|| 5126.95260000|| 20994873.04530000|| 0.02442599%|| 99.97558604%
|-
| 2520000|| 13|| 0.01220703|| 20994873.04530000|| 2563.47630000|| 20997436.52160000|| 0.01221001%|| 99.98779307%
|-
| 2730000|| 14|| 0.00610351|| 20997436.52160000|| 1281.73710000|| 20998718.25870000|| 0.00610426%|| 99.99389658%
|-
| 2940000|| 15|| 0.00305175|| 20998718.25870000|| 640.86750000|| 20999359.12620000|| 0.00305194%|| 99.99694833%
|-
| 3150000|| 16|| 0.00152587|| 20999359.12620000|| 320.43270000|| 20999679.55890000|| 0.00152592%|| 99.99847420%
|-
| 3360000|| 17|| 0.00076293|| 20999679.55890000|| 160.21530000|| 20999839.77420000|| 0.00076294%|| 99.99923713%
|-
| 3570000|| 18|| 0.00038146|| 20999839.77420000|| 80.10660000|| 20999919.88080000|| 0.00038146%|| 99.99961859%
|-
| 3780000|| 19|| 0.00019073|| 20999919.88080000|| 40.05330000|| 20999959.93410000|| 0.00019073%|| 99.99980932%
|-
| 3990000|| 20|| 0.00009536|| 20999959.93410000|| 20.02560000|| 20999979.95970000|| 0.00009536%|| 99.99990468%
|-
| 4200000|| 21|| 0.00004768|| 20999979.95970000|| 10.01280000|| 20999989.97250000|| 0.00004768%|| 99.99995236%
|-
| 4410000|| 22|| 0.00002384|| 20999989.97250000|| 5.00640000|| 20999994.97890000|| 0.00002384%|| 99.99997620%
|-
| 4620000|| 23|| 0.00001192|| 20999994.97890000|| 2.50320000|| 20999997.48210000|| 0.00001192%|| 99.99998812%
|-
| 4830000|| 24|| 0.00000596|| 20999997.48210000|| 1.25160000|| 20999998.73370000|| 0.00000596%|| 99.99999408%
|-
| 5040000|| 25|| 0.00000298|| 20999998.73370000|| 0.62580000|| 20999999.35950000|| 0.00000298%|| 99.99999706%
|-
| 5250000|| 26|| 0.00000149|| 20999999.35950000|| 0.31290000|| 20999999.67240000|| 0.00000149%|| 99.99999855%
|-
| 5460000|| 27|| 0.00000074|| 20999999.67240000|| 0.15540000|| 20999999.82780000|| 0.00000074%|| 99.99999929%
|-
| 5670000|| 28|| 0.00000037|| 20999999.82780000|| 0.07770000|| 20999999.90550000|| 0.00000037%|| 99.99999966%
|-
| 5880000|| 29|| 0.00000018|| 20999999.90550000|| 0.03780000|| 20999999.94330000|| 0.00000018%|| 99.99999984%
|-
| 6090000|| 30|| 0.00000009|| 20999999.94330000|| 0.01890000|| 20999999.96220000|| 0.00000009%|| 99.99999993%
|-
| 6300000|| 31|| 0.00000004|| 20999999.96220000|| 0.00840000|| 20999999.97060000|| 0.00000004%|| 99.99999997%
|-
| 6510000|| 32|| 0.00000002|| 20999999.97060000|| 0.00420000|| 20999999.97480000|| 0.00000002%|| 99.99999999%
|-
| 6720000|| 33|| 0.00000001|| 20999999.97480000|| 0.00210000|| 20999999.97690000|| 0.00000001%|| 100.00000000%
|-
| 6930000|| 34|| 0.00000000|| 20999999.97690000|| 0.00000000|| 20999999.97690000|| 0.00000000%|| 100.00000000%
|}
''Note: The number of bitcoins are presented in a floating point format. However, these values are based on the number of satoshi per block originally in integer format to prevent compounding error.''

''* In block 124724, user midnightmagic solo mined a block which caused one less Satoshi to be created than would otherwise have come into existence. Therefore, all calculations from this block onwards must now, to be accurate, include this underpay in total Bitcoins in existence.''

==Spendable Supply==
The theoretical total number of bitcoins, 21 million, should not be confused with the total spendable supply. The total spendable supply is always lower than the theoretical total supply, and is subject to accidental loss, willful destruction, and technical peculiarities.

One way to see a part of the destruction of coin is by collecting a sum of all unspent transaction outputs, using a [[API reference (JSON-RPC)|Bitcoin RPC]] command <code>gettxoutsetinfo</code>. The ''total_amount'' value returned is the sum of all outputs that the client deems technically spendable but not currently spent. Note however that this does not take into account outputs that are exceedingly unlikely to be spent as is the case in loss and destruction via constructed addresses, for example.
===Miner Underpay===

The algorithm which decides whether a block is valid only checks to verify whether the total amount of the reward '''exceeds''' the reward plus available fees. Therefore it is possible for a miner to deliberately choose to underpay himself by any value: not only can this destroy the fees involved, but also the reward itself, which can prevent the total possible bitcoins that can come into existence from reaching its theoretical meximum. This is a form of underpay which the reference implementation recognises as impossible to spend. Some of the other types below are not recognised as officially destroying Bitcoins; it is possible for example to spend the 1BitcoinEaterAddressDontSendf59kuE if a corresponding private key is used (although this would imply that Bitcoin has been broken.)

===Loss of bitcoin===
Bitcoins may be lost if the conditions required to spend them are no longer known. For example, if you made a transaction to an [[address]] that requires a private key in order to spend those bitcoins further, had written that private key down on a piece of paper, but that piece of paper was lost. In this case, that bitcoin may also be considered lost, as the odds of randomly finding a matching private key are such that it is generally considered impossible.

===Willful destruction of bitcoin===
Bitcoins may also be willfully 'destroyed' - for example by attaching conditions that make it impossible to spend them.

A common method is to send bitcoin to an address that was constructed and only made to pass validity checks, but for which no private key is actually known. An example of such an address is "1BitcoinEaterAddressDontSendf59kuE", where the last "f59kuE" is text to make the preceding constructed text pass validation. Finding a matching private key is, again, generally considered impossible. For an example of how difficult this would be, see [[Vanitygen#Use_of_vanitygen_to_try_to_attack_addresses|Vanitygen]].

Another common method is to send bitcoin in a transaction where the conditions for spending are not just unfathomably unlikely, but literally impossible to meet. For example, a transaction that is made [[Script#Provably_Unspendable.2FPrunable_Outputs|provably unspendable using OP_RETURN]], or uses script operations that requires the user to prove that 1+1 equals 3.

A lesser known method is to send bitcoin to an address based on private key that is outside the [[Private_key#Range_of_valid_ECDSA_private_keys|range of valid ECDSA private keys]]. For example, the address 16QaFeudRUt8NYy2yzjm3BMvG4xBbAsBFM has a known matching private key of value 0 (zero), which is outside the valid range.

===Technical peculiarities preventing spending of bitcoin===
There are also technical peculiarities that prevent the spending of some bitcoin.

The first {{btc}}50, included in the [[genesis block]], cannot be spent as its transaction is not in the global database.

In older versions of the bitcoin reference code, a miner could make their coinbase transaction (block reward) have the exact same ID as used in a previous block<ref>https://github.com/bitcoin/bitcoin/issues/612</ref>. This effectively caused the previous block reward to become unspendable. Two known such cases<ref>{{cite tx|e3bf3d07d4b0375638d5f1db5255fe07ba2c4cb067cd81b84ee974b6585fb468|used in blocks 91722 and 91880}}</ref><ref>{{cite tx|d5d27987d2a3dfc724e359870c6644b40e497bdc0589a033220fe15429d88599|used in blocks 91812 and 91842</ref> are left as special cases in the code<ref>https://github.com/bitcoin/bitcoin/commit/ab91bf39b7c11e9c86bb2043c24f0f377f1cf514</ref> as part of [[BIP 0030]] changes that fixed this issue. These transactions were {{btc}}50 each.

==Money Supply==
While the number of bitcoins in existence will never exceed 21 million, the [[wikipedia:money supply|money supply]] of bitcoins can exceed 21 million due to [[wikipedia:Fractional-reserve Banking|Fractional-reserve Banking]].

==Deflation==

Because the monetary base of bitcoins cannot be expanded, the currency would be subject to severe deflation if it becomes widely used.
Keynesian economists argue that [[Deflationary spiral|deflation]] is bad for an economy because it incentivises individuals and businesses to save money rather than invest in businesses and create jobs. The [[wikipedia:Austrian school|Austrian school]] of thought counters this criticism, claiming that as deflation occurs in all stages of production, entrepreneurs who invest benefit from it. As a result, profit ratios tend to stay the same and only their magnitudes change. In other words, in a deflationary environment, goods and services decrease in price, but at the same time the cost for the production of these goods and services tend to decrease proportionally, effectively not affecting profits. Price deflation encourages an increase in hoarding — hence savings — which in turn tends to lower interest rates and increase the incentive for entrepreneurs to invest in projects of longer term.

==See also==

* [http://www.econlib.org/library/Columns/y2006/Friedmantranscript.html Milton Friedman interview], where he proposed to replace the central bank with a computer, and to fix the money supply growth at 4% annually
* [[Deflationary spiral]]
* [http://blockchain.info/charts/total-bitcoins Chart of total bitcoins in circulation]
* [[Inflation]]
* [[Prohibited changes]]

==References==
<references />

[[Category:Economics]]

Proof of work

2015-08-26T06:20:15Z

Atheros: Rewrote two opening sentences to sound more like a human wrote them.

A '''proof of work''' is a piece of data which is difficult (costly, time-consuming) to produce but easy for others to verify and which satisfies certain requirements. Producing a proof of work can be a random process with low probability so that a lot of trial and error is required ''on average'' before a valid proof of work is generated. Bitcoin uses the [[Hashcash]] proof of work.

One application of this idea is using [http://en.wikipedia.org/wiki/Hashcash hashcash] as a method to preventing email spam, requiring a proof of work on the email's contents (including the To address), on every email. Legitimate emails will be able to do the work to generate the proof easily (not much work is required for a single email), but mass spam emailers will have difficulty generating the required proofs (which would require huge computational resources).

Hashcash proofs of work are used in Bitcoin for block generation. In order for a block to be accepted by network participants, [[Mining|miners]] must complete a proof of work which covers all of the data in the block. The [[difficulty]] of this work is adjusted so as to limit the rate at which new blocks can be generated by the network to one every 10 minutes. Due to the very low probability of successful generation, this makes it unpredictable which worker computer in the network will be able to generate the next block.

For a block to be valid it must hash to a value less than the current [[target]]; this means that each block indicates that work has been done generating it. Each block contains the hash of the preceding block, thus each block has a [[block chain|chain]] of blocks that together contain a large amount of work. Changing a block (which can only be done by making a new block containing the same predecessor) requires regenerating all successors and redoing the work they contain. This protects the block chain from tampering.

The most widely used proof-of-work scheme is based on [https://en.wikipedia.org/wiki/SHA-2 SHA-256] and was introduced as a part of [[Bitcoin]]. Some other hashing algorithms that are used for proof-of-work include scrypt, Blake-256, CryptoNight,<ref>[https://cryptonote.org/inside.php#equal-proof-of-work Equal Proof-of-Work], Cryptonote.org</ref> HEFTY1, Quark, SHA-3, scrypt-jane, scrypt-n, and combinations thereof.

== Example ==

Let's say the base string that we are going to do work on is "Hello, world!". Our target is to find a variation of it that SHA-256 hashes to a value beginning with '000'. We vary the string by adding an integer value to the end called a [[nonce]] and incrementing it each time. Finding a match for "Hello, world!" takes us 4251 tries (but happens to have zeroes in the first four digits):

"Hello, world!0" => 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64
"Hello, world!1" => e9afc424b79e4f6ab42d99c81156d3a17228d6e1eef4139be78e948a9332a7d8
"Hello, world!2" => ae37343a357a8297591625e7134cbea22f5928be8ca2a32aa475cf05fd4266b7
...
"Hello, world!4248" => 6e110d98b388e77e9c6f042ac6b497cec46660deef75a55ebc7cfdf65cc0b965
"Hello, world!4249" => c004190b822f1669cac8dc37e761cb73652e7832fb814565702245cf26ebb9e6
"Hello, world!4250" => 0000c3af42fc31103f1fdc0151fa747ff87349a4714df7cc52ea464e12dcd4e9

4251 hashes on a modern computer is not very much work (most computers can achieve at least 4 million hashes per second). Bitcoin automatically varies the [[difficulty]] (and thus the amount of work required to generate a block) to keep a roughly constant rate of block generation.

In Bitcoin things are a bit more complex, especially since the header contains the [http://en.wikipedia.org/wiki/Merkle_tree Merkle tree] which depends on the included [[transactions]]. This includes the generation transaction, a transaction "out of nowhere" to our own address, which in addition to providing the miner with incentive to do the work, also ensures that every miner hashes a unique data set.

== List of algorithms ==

=== Traditional proof of work ===
# hashcash with double iterated SHA256
# hashcash with [[scrypt]] internal hash
# [[Momentum]] birthday collision
# Cuckoo Cycle proof of work https://github.com/tromp/cuckoo
# Various other proof of works functions (e.g. [[Ethereum]] had a few candidates)

=== Proof of X ===
# [[Proof of Stake]]
# [[Proof of Burn]]

[[Category:Vocabulary]]
[[Category:Proof-of-x]]

[[fr:Preuve de travail]]

==References==
[[Distribution of nonces and hashes]]
<references/>

Proof of work

2015-08-26T06:14:19Z

Atheros: linkify SHA-256 because people really don't know what hashing algorithms are. From that page they can click "Cryptographic hash function"

A '''proof of work''' is a piece of data which was difficult (costly, time-consuming) to produce so as to satisfy certain requirements. It must be trivial to check whether data satisfies said requirements. Producing a proof of work can be a random process with low probability, so that a lot of trial and error is required ''on average'' before a valid proof of work is generated. Bitcoin uses the [[Hashcash]] proof of work.

One application of this idea is using [http://en.wikipedia.org/wiki/Hashcash hashcash] as a method to preventing email spam, requiring a proof of work on the email's contents (including the To address), on every email. Legitimate emails will be able to do the work to generate the proof easily (not much work is required for a single email), but mass spam emailers will have difficulty generating the required proofs (which would require huge computational resources).

Hashcash proofs of work are used in Bitcoin for block generation. In order for a block to be accepted by network participants, [[Mining|miners]] must complete a proof of work which covers all of the data in the block. The [[difficulty]] of this work is adjusted so as to limit the rate at which new blocks can be generated by the network to one every 10 minutes. Due to the very low probability of successful generation, this makes it unpredictable which worker computer in the network will be able to generate the next block.

For a block to be valid it must hash to a value less than the current [[target]]; this means that each block indicates that work has been done generating it. Each block contains the hash of the preceding block, thus each block has a [[block chain|chain]] of blocks that together contain a large amount of work. Changing a block (which can only be done by making a new block containing the same predecessor) requires regenerating all successors and redoing the work they contain. This protects the block chain from tampering.

The most widely used proof-of-work scheme is based on [https://en.wikipedia.org/wiki/SHA-2 SHA-256] and was introduced as a part of [[Bitcoin]]. Some other hashing algorithms that are used for proof-of-work include scrypt, Blake-256, CryptoNight,<ref>[https://cryptonote.org/inside.php#equal-proof-of-work Equal Proof-of-Work], Cryptonote.org</ref> HEFTY1, Quark, SHA-3, scrypt-jane, scrypt-n, and combinations thereof.

== Example ==

Let's say the base string that we are going to do work on is "Hello, world!". Our target is to find a variation of it that SHA-256 hashes to a value beginning with '000'. We vary the string by adding an integer value to the end called a [[nonce]] and incrementing it each time. Finding a match for "Hello, world!" takes us 4251 tries (but happens to have zeroes in the first four digits):

"Hello, world!0" => 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64
"Hello, world!1" => e9afc424b79e4f6ab42d99c81156d3a17228d6e1eef4139be78e948a9332a7d8
"Hello, world!2" => ae37343a357a8297591625e7134cbea22f5928be8ca2a32aa475cf05fd4266b7
...
"Hello, world!4248" => 6e110d98b388e77e9c6f042ac6b497cec46660deef75a55ebc7cfdf65cc0b965
"Hello, world!4249" => c004190b822f1669cac8dc37e761cb73652e7832fb814565702245cf26ebb9e6
"Hello, world!4250" => 0000c3af42fc31103f1fdc0151fa747ff87349a4714df7cc52ea464e12dcd4e9

4251 hashes on a modern computer is not very much work (most computers can achieve at least 4 million hashes per second). Bitcoin automatically varies the [[difficulty]] (and thus the amount of work required to generate a block) to keep a roughly constant rate of block generation.

In Bitcoin things are a bit more complex, especially since the header contains the [http://en.wikipedia.org/wiki/Merkle_tree Merkle tree] which depends on the included [[transactions]]. This includes the generation transaction, a transaction "out of nowhere" to our own address, which in addition to providing the miner with incentive to do the work, also ensures that every miner hashes a unique data set.

== List of algorithms ==

=== Traditional proof of work ===
# hashcash with double iterated SHA256
# hashcash with [[scrypt]] internal hash
# [[Momentum]] birthday collision
# Cuckoo Cycle proof of work https://github.com/tromp/cuckoo
# Various other proof of works functions (e.g. [[Ethereum]] had a few candidates)

=== Proof of X ===
# [[Proof of Stake]]
# [[Proof of Burn]]

[[Category:Vocabulary]]
[[Category:Proof-of-x]]

[[fr:Preuve de travail]]

==References==
[[Distribution of nonces and hashes]]
<references/>

Proof of work

2015-08-26T05:37:18Z

Atheros: Made passive sentence active.

A '''proof of work''' is a piece of data which was difficult (costly, time-consuming) to produce so as to satisfy certain requirements. It must be trivial to check whether data satisfies said requirements. Producing a proof of work can be a random process with low probability, so that a lot of trial and error is required ''on average'' before a valid proof of work is generated. Bitcoin uses the [[Hashcash]] proof of work.

One application of this idea is using [http://en.wikipedia.org/wiki/Hashcash hashcash] as a method to preventing email spam, requiring a proof of work on the email's contents (including the To address), on every email. Legitimate emails will be able to do the work to generate the proof easily (not much work is required for a single email), but mass spam emailers will have difficulty generating the required proofs (which would require huge computational resources).

Hashcash proofs of work are used in Bitcoin for block generation. In order for a block to be accepted by network participants, [[Mining|miners]] must complete a proof of work which covers all of the data in the block. The [[difficulty]] of this work is adjusted so as to limit the rate at which new blocks can be generated by the network to one every 10 minutes. Due to the very low probability of successful generation, this makes it unpredictable which worker computer in the network will be able to generate the next block.

For a block to be valid it must hash to a value less than the current [[target]]; this means that each block indicates that work has been done generating it. Each block contains the hash of the preceding block, thus each block has a [[block chain|chain]] of blocks that together contain a large amount of work. Changing a block (which can only be done by making a new block containing the same predecessor) requires regenerating all successors and redoing the work they contain. This protects the block chain from tampering.

The most widely used proof-of-work scheme is SHA-256, which was introduced by [[Bitcoin]]. Some other hashing algorithms that are used for proof-of-work include scrypt, Blake-256, CryptoNight,<ref>[https://cryptonote.org/inside.php#equal-proof-of-work Equal Proof-of-Work], Cryptonote.org</ref> HEFTY1, Quark, SHA-3, scrypt-jane, scrypt-n, and combinations thereof.

== Example ==

Let's say the base string that we are going to do work on is "Hello, world!". Our target is to find a variation of it that SHA-256 hashes to a value beginning with '000'. We vary the string by adding an integer value to the end called a [[nonce]] and incrementing it each time. Finding a match for "Hello, world!" takes us 4251 tries (but happens to have zeroes in the first four digits):

"Hello, world!0" => 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64
"Hello, world!1" => e9afc424b79e4f6ab42d99c81156d3a17228d6e1eef4139be78e948a9332a7d8
"Hello, world!2" => ae37343a357a8297591625e7134cbea22f5928be8ca2a32aa475cf05fd4266b7
...
"Hello, world!4248" => 6e110d98b388e77e9c6f042ac6b497cec46660deef75a55ebc7cfdf65cc0b965
"Hello, world!4249" => c004190b822f1669cac8dc37e761cb73652e7832fb814565702245cf26ebb9e6
"Hello, world!4250" => 0000c3af42fc31103f1fdc0151fa747ff87349a4714df7cc52ea464e12dcd4e9

4251 hashes on a modern computer is not very much work (most computers can achieve at least 4 million hashes per second). Bitcoin automatically varies the [[difficulty]] (and thus the amount of work required to generate a block) to keep a roughly constant rate of block generation.

In Bitcoin things are a bit more complex, especially since the header contains the [http://en.wikipedia.org/wiki/Merkle_tree Merkle tree] which depends on the included [[transactions]]. This includes the generation transaction, a transaction "out of nowhere" to our own address, which in addition to providing the miner with incentive to do the work, also ensures that every miner hashes a unique data set.

== List of algorithms ==

=== Traditional proof of work ===
# hashcash with double iterated SHA256
# hashcash with [[scrypt]] internal hash
# [[Momentum]] birthday collision
# Cuckoo Cycle proof of work https://github.com/tromp/cuckoo
# Various other proof of works functions (e.g. [[Ethereum]] had a few candidates)

=== Proof of X ===
# [[Proof of Stake]]
# [[Proof of Burn]]

[[Category:Vocabulary]]
[[Category:Proof-of-x]]

[[fr:Preuve de travail]]

==References==
[[Distribution of nonces and hashes]]
<references/>

Proof of work

2015-08-26T05:30:27Z

Atheros: removed broken link

A '''proof of work''' is a piece of data which was difficult (costly, time-consuming) to produce so as to satisfy certain requirements. It must be trivial to check whether data satisfies said requirements. Producing a proof of work can be a random process with low probability, so that a lot of trial and error is required ''on average'' before a valid proof of work is generated. Bitcoin uses the [[Hashcash]] proof of work.

One application of this idea is using [http://en.wikipedia.org/wiki/Hashcash hashcash] as a method to preventing email spam, requiring a proof of work on the email's contents (including the To address), on every email. Legitimate emails will be able to do the work to generate the proof easily (not much work is required for a single email), but mass spam emailers will have difficulty generating the required proofs (which would require huge computational resources).

Hashcash proofs of work are used in Bitcoin for block generation. Proofs of work that are tied to the data of each block are required for the blocks to be accepted. The [[difficulty]] of this work is adjusted so as to limit the rate at which new blocks can be generated by the network to one every 10 minutes. Due to the very low probability of successful generation, this makes it unpredictable which worker computer in the network will be able to generate the next block.

For a block to be valid it must hash to a value less than the current [[target]]; this means that each block indicates that work has been done generating it. Each block contains the hash of the preceding block, thus each block has a [[block chain|chain]] of blocks that together contain a large amount of work. Changing a block (which can only be done by making a new block containing the same predecessor) requires regenerating all successors and redoing the work they contain. This protects the block chain from tampering.

The most widely used proof-of-work scheme is SHA-256, which was introduced by [[Bitcoin]]. Some other hashing algorithms that are used for proof-of-work include scrypt, Blake-256, CryptoNight,<ref>[https://cryptonote.org/inside.php#equal-proof-of-work Equal Proof-of-Work], Cryptonote.org</ref> HEFTY1, Quark, SHA-3, scrypt-jane, scrypt-n, and combinations thereof.

== Example ==

Let's say the base string that we are going to do work on is "Hello, world!". Our target is to find a variation of it that SHA-256 hashes to a value beginning with '000'. We vary the string by adding an integer value to the end called a [[nonce]] and incrementing it each time. Finding a match for "Hello, world!" takes us 4251 tries (but happens to have zeroes in the first four digits):

"Hello, world!0" => 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64
"Hello, world!1" => e9afc424b79e4f6ab42d99c81156d3a17228d6e1eef4139be78e948a9332a7d8
"Hello, world!2" => ae37343a357a8297591625e7134cbea22f5928be8ca2a32aa475cf05fd4266b7
...
"Hello, world!4248" => 6e110d98b388e77e9c6f042ac6b497cec46660deef75a55ebc7cfdf65cc0b965
"Hello, world!4249" => c004190b822f1669cac8dc37e761cb73652e7832fb814565702245cf26ebb9e6
"Hello, world!4250" => 0000c3af42fc31103f1fdc0151fa747ff87349a4714df7cc52ea464e12dcd4e9

4251 hashes on a modern computer is not very much work (most computers can achieve at least 4 million hashes per second). Bitcoin automatically varies the [[difficulty]] (and thus the amount of work required to generate a block) to keep a roughly constant rate of block generation.

In Bitcoin things are a bit more complex, especially since the header contains the [http://en.wikipedia.org/wiki/Merkle_tree Merkle tree] which depends on the included [[transactions]]. This includes the generation transaction, a transaction "out of nowhere" to our own address, which in addition to providing the miner with incentive to do the work, also ensures that every miner hashes a unique data set.

== List of algorithms ==

=== Traditional proof of work ===
# hashcash with double iterated SHA256
# hashcash with [[scrypt]] internal hash
# [[Momentum]] birthday collision
# Cuckoo Cycle proof of work https://github.com/tromp/cuckoo
# Various other proof of works functions (e.g. [[Ethereum]] had a few candidates)

=== Proof of X ===
# [[Proof of Stake]]
# [[Proof of Burn]]

[[Category:Vocabulary]]
[[Category:Proof-of-x]]

[[fr:Preuve de travail]]

==References==
[[Distribution of nonces and hashes]]
<references/>

Fractional Reserve Banking and Bitcoin

2014-10-10T19:37:57Z

Atheros: Moved mention of CoinLenders out of the top text down to where it makes more sense in the Keynesian section.

While Fractional Reserve Banking with Bitcoin is possible, there is [https://bitcointalk.org/index.php?topic=51899.0 disagreement] over what it would entail. Much discussion occurred on the [[Talk:Myths#Fractional_reserve_banking_with_Bitcoin_is_fundamentally_different|Myths Talk Page]].

==Keynesian Viewpoint==
Fractional Reserve Banking with Bitcoin is possible and practical. It is already implemented with [https://coinlenders.com CoinLenders]. There is no fundamental difference between classical currencies and Bitcoin as it applies to banking. Banks will still be free to take in bitcoins and present them to customers as "available for withdrawal" while still lending most of those bitcoins to a different customer for a profit. Some of those bitcoins will be held in reserves in case of a bank run. It will be up to the bank to hold a sufficient supply of reserves in order to prevent insolvency in the event of a bank run. Central banks were established to enforce reserve requirements and so, with Bitcoin lacking a central bank, some banks will almost surely collapse, taking their customers' deposits with them. A large bitcoin exchange could tomorrow lend out 10,000 bitcoins to an individual to start a business. The [http://www.federalreserve.gov/faqs/money_12845.htm money supply] would thus increase by 10,000 and we would instantly have Fractional Reserve Banking. The same amount of bitcoins would still exist in the [[Block Chain]], but the body of people participating in the Bitcoin economy would have the perception that more bitcoins exist. If the value of a bitcoin is stable for a long period of time, then Fractional Reserve Banking is ''inevitable''. 

See [http://en.wikipedia.org/wiki/Fractional-reserve_banking Fractional reserve banking].

The Monetary Base of Bitcoin is limited to 21 million. But because Fractional Reserve Banking is possible, the money supply of bitcoins (which includes demand deposits) can exceed 21 million by a factor of x where x is the [http://en.wikipedia.org/wiki/Money_multiplier Money Multiplier].

==Austrian Viewpoint==

According to the [http://wiki.mises.org/wiki/Fractional_reserve_banking Austrian viewpoint]:
<blockquote>Fractional-reserve banking (or FRB) is the widespread banking practice in which only a fraction of a bank's demand deposits are kept in reserve and available for immediate withdrawal (as cash and other highly liquid assets), whilst the remaining cash is lent out to borrowers (and so is never actually available for immediate withdrawal to legitimate deposit-holders).</blockquote>

In order for fractional reserve banking to affect the money supply, the debt instruments issued by the bank (for example, bank notes or demand deposits) must be accepted as if they were money proper, in other words, they must be money-substitutes. This is explained for example by [http://mises.org/rothbard/austrianmoneysupply.pdf Rothbard in Austrian Definitions of the Supply of Money]:

<blockquote>And so long as demand deposits are accepted as equivalent to standard money, they will function as part of the money supply.

It is important to recognize that demand deposits are not automatically part of the money supply by virtue of their very existence; they continue as equivalent to money only so long as the subjective estimates of the sellers of goods on the market think that they are so equivalent and accept them as such in exchange.</blockquote>

In the historical cases of money based on gold or government issued fiat, the reason why money-substitutes are accepted as if they were money proper is that the money proper has in some circumstances high transaction costs (for example, gold might be too heavy to carry around, or the buyer and seller are not at the same location and want to perform the exchange electronically), or are not legally permitted (normal people are not allowed to obtain central bank reserves). This creates a demand for forms of money which have lower transaction costs. With gold/fiat, this requires the creation of debt instruments, which then, after being generally accepted in exchange, become money substitutes and a part of the money supply.

The situation with Bitcoin is different, because other forms can be created without debt instruments, for example [[Casascius physical bitcoins]] or [[Bitbills]]. Bitcoin in its "classical" form is similar in function of a bank account (allowing electronic transfers of balances) even though there is no debt instrument. Any object that can store 64 bytes of data (size of Bitcoin keypair) can, hypothetically, be used as a form of Bitcoin. In some cases, shorter forms than 64 bytes are possible too (for example, [[Mini_private_key_format|mini private key format]] used by Casascius physical bitcoins). Issuers of Bitcoin-based debt instruments, if they expect these instruments to be accepted in exchange, need to create demand for them as a method of payment outside of the Bitcoin network. This is difficult, because a transaction that occurs outside of the Bitcoin network is incompatible with it, so people equipped with software for handling only pure Bitcoin transactions cannot accept it. Furthermore, they also would need to compete against not only Bitcoin, but against other currencies, payment methods and services.

Currently, Bitcoin based debt instruments are restricted to a narrow field of uses. Exchanges allow these instruments to be traded against other currencies. E-wallets allow inter-wallet transfers. GLBSE allows the floating of shares or other contractual arrangements. However, these debt instruments are, in general, outside of these narrow fields, not accepted for exchange as if they were native Bitcoins. They rarely even circulate outside of the internal transactions of the providers of these services. There are very few exceptions, such as the redeemable Mt. Gox code. If the service provider attempted to conduct FRB by overissuing these instruments, they would be exposed at risk of having them redeemed too quickly. One possible way of mitigating this risk is to institute a suspension of specie payments (for example, Mt. Gox. having a default withdrawal limit).

If in the future, P2P exchanges and distributed wallets are available (both have been suggested already at bitcointalk.org forums), this would decrease the demand for Bitcoin-based debt instruments even further.

Historically, in all known situations where an overissue of Bitcoin-based debt instruments was produced, this resulted either in a voluntary elimination of the excess instruments (Mt. Gox hack from June 2011), bankruptcy (the demise of mybitcoin) or a new investor bailout (the demise of bitomat.pl and subsequent takeover by Mt. Gox). Here we have empirical evidence that FRB with Bitcoin is possible.

Putting all this together, there are several steps that need to be addressed regarding Bitcoin-FRB and money supply:

# overissue of debt instruments (this would cause FRB)
# general acceptance of these instruments as a method of payment (this would mean the instruments need to be included in the money supply)
# market price of these instruments at a different rate than the reserve ratio of the issuer (this would cause inflation or deflation)

Even if we assume that an overissue is possible in long term, there are significant obstacles in phase 2 and 3, as elaborated above. It is therefore unlikely that even if Bitcoin-FRB became widespread, this would significantly affect the money supply of Bitcoins or inflation/deflation.
[[Category:Economics]]

Myths

2014-10-10T19:34:59Z

Atheros: /* It's a giant ponzi scheme */

Let's clear up some common Bitcoin misconceptions.

== Bitcoin is just like all other digital currencies; nothing new ==

Nearly all other digital currencies are centrally controlled. This means that:
* They can be printed at the subjective whims of the controllers
* They can be destroyed by attacking the central point of control
* Arbitrary rules can be imposed upon their users by the controllers

Being decentralized, Bitcoin solves all of these problems.

== Bitcoins don't solve any problems that fiat currency and/or gold doesn't solve ==

Unlike gold, bitcoins are:
* Easy to transfer
* Easy to secure
* Easy to verify
* Easy to granulate

Unlike fiat currencies, bitcoins are:
* Predictable and limited in [[Controlled_Currency_Supply|supply]]
* Not controlled by a central authority (such as [http://en.wikipedia.org/wiki/Federal_Reserve The United States Federal Reserve])
* Not debt-based

Unlike electronic fiat currency systems, bitcoins are:
* Potentially anonymous
* Freeze-proof
* Faster to transfer
* Cheaper to transfer

== Bitcoin is backed by processing power ==

It is not correct to say that Bitcoin is "backed by" processing power. A currency being "backed" means that it is pegged to something else via a central party at a certain exchange rate yet you cannot exchange bitcoins for the computing power that was used to create them. Bitcoin is in this sense not backed by anything. It is a currency in its own right. Just as gold is not backed by anything, the same applies to Bitcoin.

The Bitcoin currency is ''created'' via processing power, and the integrity of the block chain is ''protected'' by the existence of a network of powerful computing nodes from certain [[Weaknesses#Attacker_has_a_lot_of_computing_power|attacks]].

== Bitcoins are worthless because they aren't backed by anything ==

One could argue that gold isn't backed by anything either. Bitcoins have properties resulting from the system's design that allows them to be subjectively valued by individuals. This valuation is demonstrated when individuals freely exchange for or with bitcoins. Please refer to the [http://en.wikipedia.org/wiki/Subjective_theory_of_value Subjective Theory of Value].

See also: the "[[#Bitcoin_is_backed_by_processing_power|Bitcoin is backed by processing power]]" myth.

== The value of bitcoins are based on how much electricity and computing power it takes to mine them ==

This statement is an attempt to apply to Bitcoin the [http://en.wikipedia.org/wiki/Labor_theory_of_value labor theory of value], which is generally accepted as false. Just because something takes X resources to create does not mean that the resulting product will be worth X. It can be worth more, or less, depending on the utility thereof to its users.

In fact the causality is the reverse of that (this applies to the labor theory of value in general). The cost to mine bitcoins is based on how much they are worth. If bitcoins go up in value, more people will mine (because [[Mining|mining]] is profitable), thus [[difficulty]] will go up, thus the cost of mining will go up. The inverse happens if bitcoins go down in value. These effects balance out to cause mining to always cost an amount proportional to the value of bitcoins it produces.

== Bitcoins have no intrinsic value (unlike some other things) ==

This is simply not true. Each bitcoin gives the holder the ability to embed a large number of short in-transaction messages in a globally distributed and timestamped permanent data store, namely the bitcoin blockchain. There is no other similar datastore which is so widely distributed. There is a tradeoff between the exact number of messages and how quickly they can be embedded. But as of December 2013, it's fair to say that one bitcoin allows around 1000 such messages to be embedded, each within about 10 minutes of being sent, since a fee of 0.001 BTC is enough to get transactions confirmed quickly. This message embedding certainly has intrinsic value since it can be used to prove ownership of a document at a certain time, by including a one-way hash of that document in a transaction. Considering that electronic notarization services charge something like $10/document, this would give an intrinsic value of around $10,000 per bitcoin.

While some other tangible commodities do have intrinsic value, that value is generally much less than its trading price. Consider for example that gold, if it were not used as an inflation-proof store of value, but rather only for its industrial uses, would certainly not be worth what it is today, since the industrial requirements for gold are far smaller than the available supply thereof.

In any event, while historically intrinsic value, as well as other attributes like divisibility, fungibility, scarcity, durability, helped establish certain commodities as mediums of exchange, it is certainly not a prerequisite. While bitcoins are accused of lacking 'intrinsic value' in this sense, they make up for it in spades by possessing the other qualities necessary to make it a good medium of exchange, equal to or better than [http://en.wikipedia.org/wiki/Commodity_money commodity money].

Another way to think about this is to consider the value of bitcoin the global network, rather than each bitcoin in isolation. The value of an individual telephone is derived from the network it is connected to. If there was no phone network, a telephone would be useless. Similarly the value of an individual bitcoin derives from the global network of bitcoin-enabled merchants, exchanges, wallets, etc... Just like a phone is necessary to transmit vocal information through the network, a bitcoin is necessary to transmit economic information through the network.

Value is ultimately determined by what people are willing to trade for - by supply and demand.

== Bitcoins are illegal because they're not legal tender ==
In March 2013, the U.S. [http://en.wikipedia.org/wiki/Financial_Crimes_Enforcement_Network Financial Crimes Enforcement Network] issues a new set of guidelines on "de-centralized virtual currency", clearly targeting Bitcoin. Under the new guidelines, "a user of virtual currency is not a Money Services Businesses (MSB) under FinCEN's regulations and therefore is not subject to MSB registration, reporting, and record keeping regulations." <ref>[http://arstechnica.com/tech-policy/2013/03/us-regulator-bitcoin-exchanges-must-comply-with-money-laundering-laws/ US regulator: Bitcoin exchanges must comply with money-laundering laws | Ars Technica]</ref> [[Mining|Miners]], when mining bitcoins for their own personal use, aren't required to register as a MSB or Money Transmitter. <ref>[http://fincen.gov/news_room/rp/rulings/html/FIN-2014-R001.html Application of FinCEN’s Regulations to Virtual Currency Mining Operations | Fincen]</ref>

In general, there are a [http://en.wikipedia.org/wiki/Local_currency number of currencies] in existence that are not official government-backed currencies. A currency is, after all, nothing more than a convenient unit of account. While national laws may vary from country to country, and you should certainly check the laws of your jurisdiction, in general trading in any commodity, including digital currency like Bitcoin, [http://en.wikipedia.org/wiki/BerkShares BerkShares], game currencies like WoW gold, or Linden dollars, is not illegal.

== Bitcoin is a form of domestic terrorism because it only harms the economic stability of the USA and its currency ==

According to [http://en.wikipedia.org/wiki/Definitions_of_terrorism#United_States the definition of terrorism in the United States], you need to do violent activities to be considered a terrorist for legal purposes. Recent off-the-cuff remarks by politicians have no basis in law or fact.

Also, Bitcoin isn't domestic to the US or any other country. It's a worldwide community, as can be seen in this [https://bitcointalk.org/?topic=2346.0 map of Bitcoin nodes].

== Bitcoin will only enable tax evaders which will lead to the eventual downfall of civilization ==

Cash transactions hold the same level of anonymity but are still taxed successfully. It is up to you to follow the applicable state laws in your home country, or face the consequences.

While it may be easy to transfer bitcoins anonymously, ''spending'' them anonymously on tangibles is just as hard as spending any other kind of money anonymously. Tax evaders are often caught because their lifestyle and assets are inconsistent with their reported income, and not necessarily because government is able to follow their money.

== Bitcoins can be printed/minted by anyone and are therefore worthless ==

Bitcoins are not printed/minted. Instead, [[Blocks]] are computed by miners and for their efforts they are awarded a specific amount of bitcoins and transaction fees paid by others. See [[Mining]] for more information on how this process works.

== Bitcoins are worthless because they're based on unproven cryptography ==

SHA256 and ECDSA which are used in Bitcoin are well-known industry standard algorithms. SHA256 is endorsed and used by the US Government and is standardized (FIPS180-3 Secure Hash Standard). If you believe that these algorithms are untrustworthy then you should not trust Bitcoin, credit card transactions or any type of electronic bank transfer. Bitcoin has a sound basis in well understood cryptography.

== Early adopters are unfairly rewarded ==

Early adopters are rewarded for taking the higher risk with their time and money. The capital invested in bitcoin at each stage of its life invigorated the community and helped the currency to reach subsequent milestones. Arguing that early adopters do not deserve to profit from this is akin to saying that early investors in a company, or people who buy stock at a company IPO (Initial Public Offering), are unfairly rewarded.

This argument also depends on bitcoin early adopters using bitcoins to store rather than transfer value. The daily trade on the exchanges (as of Jan 2012) indicates that smaller transactions are becoming the norm, indicating trade rather than investment. In more pragmatic terms, "fairness" is an arbitrary concept that is improbable to be agreed upon by a large population. Establishing "fairness" is no goal of Bitcoin, as this would be impossible.

Looking forwards, considering the amount of publicity bitcoin received as of April 2013, there can be no reasonable grounds for complaint for people who did not invest at that time, and then see the value (possibly) rising drastically higher.

By starting to mine or acquire bitcoins today, you too can become an early adopter.

== 21 million coins isn't enough; doesn't scale ==

One Bitcoin is divisible down to eight decimal places. There are really 2,099,999,997,690,000 (just over 2 quadrillion) maximum possible atomic units in the bitcoin system.

The value of "1 BTC" represents 100,000,000 of these. In other words, each bitcoin is divisible by up to 108.

As the value of the unit of 1 BTC grew too large to be useful for day to day transactions, people started dealing in smaller [[Units|units]], such as milli-bitcoins (mBTC) or micro-bitcoins (μBTC).

== Bitcoins are stored in wallet files, just copy the wallet file to get more coins! ==

No, your wallet contains your secret keys, giving you the rights to spend your bitcoins. Think of it like having bank details stored in a file. If you give your bank details (or bitcoin wallet) to someone else, that doesn't double the amount of money in your account. You can spend your money or they can spend your money, but not both.

== Lost coins can't be replaced and this is bad ==

Bitcoins are divisible to 0.00000001, so there being fewer bitcoins remaining is not a problem for the currency itself. If you lose your coins, all other coins will go up in value a little. Consider it a donation to all other bitcoin users.

A related question is: Why don't we have a mechanism to replace lost coins? The answer is that it is impossible to distinguish between a 'lost' coin and one that is simply sitting unused in someone's wallet.

== It's a giant ponzi scheme ==
In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. In a ponzi scheme, early adopters can only profit at the expense of late adopters, and the late adopters always lose. Bitcoin can have a win-win outcome. Earlier adopters profit from the rise in value as Bitcoin becomes better understood and in turn demanded by the public at large. All adopters benefit from the usefulness of a reliable and widely-accepted decentralized peer-to-peer currency.

It is also important to note that [[Satoshi Nakamoto]], creator of bitcoin, has never spent a bitcoin (other than giving them away when they were worthless) which we can verify by checking the blockchain.

== Finite coins plus lost coins means deflationary spiral ==
As deflationary forces may apply, economic factors such as hoarding are offset by human factors that may lessen the chances that a [[Deflationary spiral]] will occur.

== Bitcoin can't work because there is no way to control inflation ==

Inflation is simply a rise of prices over time, which is generally the result of the devaluing of a currency. This is a function of supply and demand. Given the fact that the supply of bitcoins is fixed at a certain amount, unlike fiat money, the only way for inflation to get out of control is for demand to disappear. Temporary inflation is possible with a rapid adoption of Fractional Reserve Banking but will stabilize once a substantial number of the 21 million "hard" bitcoins are stored as reserves by banks.

Given the fact that Bitcoin is a distributed system of currency, if demand were to decrease to almost nothing, the currency would be doomed anyway.

The key point here is that Bitcoin as a currency can't be inflated by any single person or entity, like a government, as there's no way to increase supply past a certain amount.

Indeed, the most likely scenario, as Bitcoin becomes more popular and demand increases, is for the currency to increase in value, or deflate, until demand stabilizes.

== The Bitcoin community consists of anarchist/conspiracy theorist/gold standard 'weenies' ==

The members of the community vary in their ideological stances. While it may have been started by ideological enthusiasts, Bitcoin now speaks to a large number of regular pragmatic folk, who simply see its potential for reducing the costs and friction of global e-commerce.

== Anyone with enough computing power can take over the network ==

CONFIRMED, see [[Weaknesses]].

That said, as the network grows, it becomes harder and harder for a single entity to do so. Already the Bitcoin network's computing power is quite ahead of the world's fastest supercomputers, together.

What an attacker can do once the network is taken over is quite limited. Under no circumstances could an attacker create counterfeit coins, fake transactions, or take anybody else's money. An attacker's capabilities are limited to taking back their own money that they very recently spent, and preventing other people's transactions from receiving confirmations. Such an attack would be very costly in resources, and for such meager benefits there is little rational economic incentive to do such a thing.

Furthermore, this attack scenario would only be feasible for as long as it was actively underway. As soon as the attack stopped, the network would resume normal operation.

== Bitcoin violates governmental regulations ==

There is no known governmental regulation which disallows the use of Bitcoin.

See also: the "[[#Bitcoins_are_illegal_because_they.27re_not_legal_tender|Bitcoins are illegal because they're not legal tender]]" myth.

== Fractional reserve banking is not possible ==

It is possible. See the main article, [[Fractional Reserve Banking and Bitcoin]]

== After 21 million coins are mined, no one will generate new blocks ==

When operating costs can't be covered by the block creation bounty, which will happen some time before the total amount of BTC is reached, miners will earn some profit from [[transaction fees]]. However unlike the block reward, there is [http://bitcoin.stackexchange.com/questions/876/how-much-will-transaction-fees-eventually-be/895#895 no coupling between transaction fees and the need for security], so there is less of a guarantee that the amount of [[Mining|mining]] being performed will be sufficient to maintain the network's security.

== Bitcoin has no built-in chargeback mechanism, and this isn't good ==

'''Why some people think this is bad''': Chargebacks are useful for limiting fraud. The person handling your money has a responsibility to prevent fraud. If you buy something on eBay and the seller never ships it, PayPal takes funds from the seller's account and gives you back the money. This strengthens the eBay economy, because people recognize that their risk is limited and are more willing to purchase items from risky sellers.

'''Why it's actually a good thing''': Bitcoin is designed such that your money is yours and yours alone. Allowing chargebacks implies that it is possible for another entity to take your money from you. You can have either total ownership rights of your money, or fraud protection, but not both. That said, nothing inherent in the dollar or euro or any other currency is necessary for chargebacks to be possible, and likewise, nothing prevents the creation of PayPal-like services denominated in Bitcoin that provide chargebacks or fraud protection.

The statement "The person handling your money has a responsibility to prevent fraud" is still true; the power has been shifted into your own hands. Fraud will always exist. It's up to you to only send bitcoins to trusted entities. It is possible to trust an online identity without ever knowing their physical identity; see the [http://wiki.bitcoin-otc.com/wiki/OTC_Rating_System OTC Web of Trust].

== Quantum computers would break Bitcoin's security ==

While ECDSA is indeed not secure under quantum computing, quantum computers don't yet exist and probably won't for a while.
The DWAVE system often written about in the press is, even if all their claims are true, not a quantum computer of a kind that could be used for cryptography.
Bitcoin's security, when used properly with a new address on each transaction, depends on more than just ECDSA: Cryptographic hashes are much stronger than ECDSA under QC.
Bitcoin's security was designed to be upgraded in a forward compatible way and could be [http://en.wikipedia.org/wiki/Post-quantum_cryptography upgraded] if this were considered an imminent threat.

See the implications of quantum computers on public key cryptography here http://en.wikipedia.org/wiki/Quantum_computer#Potential

The ''risk'' of quantum computers is also there for financial institutions, like banks, because they heavily rely on cryptography when doing transactions.

== Bitcoin makes self-sufficient artificial intelligence possible ==
[[StorJ]]<ref>[http://garzikrants.blogspot.com/2013/01/storj-and-bitcoin-autonomous-agents.html StorJ And Bitcoin Autonomous Agents]</ref>, a theorized autonomous agent which utilizes humans to build itself and issues autonomous payments for improvement work done, is not a conscious entity. Whatever AI is possible, is not going to be magically more possible simply because it could incentivize human behaviour with pseudonymous Bitcoin payments.

== [[Mining|Bitcoin mining]] is a waste of energy and harmful for ecology ==
No more so than the wastefulness of mining gold out of the ground, melting it down and shaping it into bars, and then putting it back underground again. Not to mention the building of big fancy buildings, the waste of energy printing and minting all the various fiat currencies, the transportation thereof in armored cars by no less than two security guards for each who could probably be doing something more productive, etc.

As far as mediums of exchange go, Bitcoin is actually quite economical of resources, compared to others.

'''Economic Argument 1'''

[[Mining|Bitcoin mining]] is a highly competitive, dynamic, almost [http://en.wikipedia.org/wiki/Perfect_market perfect], market. Mining rigs can be set up and dismantled almost anywhere in the world with relative ease. Thus, market forces are constantly pushing mining activity to ''places'' and ''times'' where the marginal price of electricity is low or zero. These electricity products are cheap for a reason. Often it’s because the electricity is difficult (and wasteful) to transport, difficult to store, or because there is low demand and high supply. Using electricity in this way is a lot less wasteful than simply plugging a mining rig into the mains indiscriminately.

For example, Iceland produces an excess of cheap electricity from renewable sources, but it has no way of exporting electricity because of its remote location. It is conceivable that at some point in future Bitcoin mining will only be profitable in places like Iceland, and unprofitable in places like central Europe, where electricity comes mostly from nuclear and fossil sources.

Market forces could even push mining into innovative solutions that have an effective electricity consumption of ''zero''. Mining always produces heat equivalent to the energy consumed - for example, 1000 watts of mining equipment produces the same amount of heat as a 1000 watt heating element used in an electric space heater, hot tub, water heater, or similar appliance. Someone already in a willing position to incur the cost of electricity for its heat value alone could run mining equipment specially designed to mine bitcoins while capturing and utilizing the heat produced, without incurring any energy costs beyond what they already intended to spend on heating.

(Note that this is just an example; mining will not always produce heat equivalent to the energy consumed because some energy is inevitably released as electromagnetic radiation, among others.)

'''Economic Argument 2'''

When the environmental costs of mining are considered, they need to be weighed up against the benefits. If you question Bitcoin on the grounds that it consumes electricity, then you should also ask questions like this: Will Bitcoin promote economic growth by freeing up trade? Will this speed up the rate of technological innovation? Will this lead to faster development of green technologies? Will Bitcoin enable new, border crossing [http://en.wikipedia.org/wiki/Smart_grid smart grid] technologies? …

Dismissal of Bitcoin because of its costs, while ignoring its benefits, is a dishonest argument. In fact, any environmental argument of this type is dishonest, not just pertaining to Bitcoin. Along similar lines, it could be argued that wind turbines are bad for the environment because making the steel structure consumes energy.

'''Ratio of Capital Costs versus Electrical Costs'''

The BFL Jalapeno hashes at 5.5 Gh/s using 30W. That device consumes about $40 per year in electricity (using U.S. residential average of about $0.15 per kWh.) But the device costs over $300 including shipping. Thus just about a quarter of all costs over a two-year useful life goes to electricity. This compares to GPUs where more than 90% of costs over a two-year life went to electricity. Even more efficient designs can be expected in the future.

== Shopkeepers can't seriously set prices in bitcoins because of the volatile exchange rate ==

The assumption is that bitcoins must be sold immediately to cover operating expenses. If the shopkeeper's back-end expenses were transacted in bitcoins as well, then the exchange rate would be irrelevant. Larger adoption of Bitcoin would make prices [http://en.wikipedia.org/wiki/Sticky_%28economics%29 sticky]. Future volatility is expected to decrease, as the size and depth of the market grows.

In the meantime, many merchants simply regularly pull the latest market rates from the exchanges and automatically update the prices on their websites. Also you might be able to buy a put option in order to sell at a fixed rate for a given amount of time. This would protect you from drops in price and simplify your operations for that time period.

== Like Flooz and e-gold, bitcoins serve as opportunities for criminals and will be shut down ==

* Visa, MasterCard, PayPal, and cash all serve as opportunities for criminals as well, but society keeps them around due to their recognized net benefit.
* Hopefully Bitcoin will grow to the point where no single organization can disrupt the network, or would be better served by helping it.
* Terrorists fly aircraft into buildings, but the governments have not yet abolished consumer air travel. Obviously the public good outweighs the possible bad in their opinion.
* Criminal law differs between jurisdictions.

== Bitcoins will be shut down by the government just like Liberty Dollars were ==

Liberty Dollars started as a commercial venture to establish an alternative US currency, including physical banknotes and coins, backed by precious metals. This, in and of itself, is not illegal. They were prosecuted under counterfeiting laws because the silver coins allegedly resembled US currency.

Bitcoins do not resemble the currency of the US or of any other nation in any way, shape, or form. The word "dollar" is not attached to them in any way. The "$" symbol is not used in any way.

Bitcoins have no representational similarity whatsoever to US dollars.

Of course, actually 'shutting down' Liberty Dollars was as easy as arresting the head of the company and seizing the offices and the precious metals used as backing. The decentralized Bitcoin, with no leader, no servers, no office, and no tangible asset backing, does not have the same vulnerability.

== Bitcoin is not decentralized because the developers can dictate the software's behavior ==

The Bitcoin protocol was originally defined by Bitcoin's inventor, [[Satoshi Nakamoto]], and this protocol has now been widely accepted as the standard by the community of miners and users.

Though the developers of the original Bitcoin client still exert influence over the Bitcoin community, their power to arbitrarily modify the protocol is very limited. Since the release of Bitcoin v0.3, changes to the protocol have been minor and always in agreement with community consensus.

Protocol modifications, such as increasing the block award from 25 to 50 BTC, are not compatible with clients already running in the network. If the developers were to release a new client that the majority of miners perceives as corrupt, or in violation of the project’s aims, that client would simply not catch on, and the few users who do try to use it would find that their transactions get rejected by the network.

There are also other [[:Category:Clients|Bitcoin clients made by other developers]] that adhere to the Bitcoin protocol. As more developers create alternative clients, less power will lie with the developers of the original Bitcoin client.

== Bitcoin is a pyramid scheme ==

Bitcoin is nearly opposite of a pyramid scheme in a mathematical sense. Because Bitcoins are algorithmically made scarce, no exponential benefit is derived from introducing new users to use of it. There is a quantitative benefit in having additional interest or demand, but this is in no way exponential.

== Bitcoin was hacked ==

In the history of Bitcoin, there has never been an attack on the [[block chain]] that resulted in stolen money from a confirmed output. Neither has there ever been a reported theft resulting directly from a vulnerability in the [[Original Bitcoin client|original Bitcoin client]], or a vulnerability in the protocol. Bitcoin is secured by standard cryptographic functions. These functions have been peer reviewed by cryptography experts and are considered unlikely to be breakable in the foreseeable future.

It is safe to say that the currency itself has never been 'hacked'. However, several major ''websites'' using the currency have been hacked, often resulting in high profile Bitcoin heists. These heists are misreported in some media as hacks on Bitcoin itself. An analogy: Just because someone stole US dollars from a supermarket till, doesn’t mean that the US dollar as a currency has been 'hacked'.

Most bitcoin thefts are the result of inadequate [[Securing your wallet|wallet security]]. In response to the wave of thefts in 2011 and 2012, the community has developed risk-mitigating measures such as [[Wallet_encryption|wallet encryption]], support for [[BIP_0011|multiple signatures]], [[How_to_set_up_a_secure_offline_savings_wallet|offline wallets]], [[Paper_wallet|paper wallets]], and [[Hardware_wallet|hardware wallets]]. As these measures gain adoption by merchants and users, the number of thefts drop.

==References==
<references/>

[[de:Mythen]]
[[ru:Мифы о биткоине]]

Myths

2014-10-10T19:32:07Z

Atheros: /* It's a giant ponzi scheme */ "Bitcoin has an expected win-win outcome." By whom? This sentence is passive.

Let's clear up some common Bitcoin misconceptions.

== Bitcoin is just like all other digital currencies; nothing new ==

Nearly all other digital currencies are centrally controlled. This means that:
* They can be printed at the subjective whims of the controllers
* They can be destroyed by attacking the central point of control
* Arbitrary rules can be imposed upon their users by the controllers

Being decentralized, Bitcoin solves all of these problems.

== Bitcoins don't solve any problems that fiat currency and/or gold doesn't solve ==

Unlike gold, bitcoins are:
* Easy to transfer
* Easy to secure
* Easy to verify
* Easy to granulate

Unlike fiat currencies, bitcoins are:
* Predictable and limited in [[Controlled_Currency_Supply|supply]]
* Not controlled by a central authority (such as [http://en.wikipedia.org/wiki/Federal_Reserve The United States Federal Reserve])
* Not debt-based

Unlike electronic fiat currency systems, bitcoins are:
* Potentially anonymous
* Freeze-proof
* Faster to transfer
* Cheaper to transfer

== Bitcoin is backed by processing power ==

It is not correct to say that Bitcoin is "backed by" processing power. A currency being "backed" means that it is pegged to something else via a central party at a certain exchange rate yet you cannot exchange bitcoins for the computing power that was used to create them. Bitcoin is in this sense not backed by anything. It is a currency in its own right. Just as gold is not backed by anything, the same applies to Bitcoin.

The Bitcoin currency is ''created'' via processing power, and the integrity of the block chain is ''protected'' by the existence of a network of powerful computing nodes from certain [[Weaknesses#Attacker_has_a_lot_of_computing_power|attacks]].

== Bitcoins are worthless because they aren't backed by anything ==

One could argue that gold isn't backed by anything either. Bitcoins have properties resulting from the system's design that allows them to be subjectively valued by individuals. This valuation is demonstrated when individuals freely exchange for or with bitcoins. Please refer to the [http://en.wikipedia.org/wiki/Subjective_theory_of_value Subjective Theory of Value].

See also: the "[[#Bitcoin_is_backed_by_processing_power|Bitcoin is backed by processing power]]" myth.

== The value of bitcoins are based on how much electricity and computing power it takes to mine them ==

This statement is an attempt to apply to Bitcoin the [http://en.wikipedia.org/wiki/Labor_theory_of_value labor theory of value], which is generally accepted as false. Just because something takes X resources to create does not mean that the resulting product will be worth X. It can be worth more, or less, depending on the utility thereof to its users.

In fact the causality is the reverse of that (this applies to the labor theory of value in general). The cost to mine bitcoins is based on how much they are worth. If bitcoins go up in value, more people will mine (because [[Mining|mining]] is profitable), thus [[difficulty]] will go up, thus the cost of mining will go up. The inverse happens if bitcoins go down in value. These effects balance out to cause mining to always cost an amount proportional to the value of bitcoins it produces.

== Bitcoins have no intrinsic value (unlike some other things) ==

This is simply not true. Each bitcoin gives the holder the ability to embed a large number of short in-transaction messages in a globally distributed and timestamped permanent data store, namely the bitcoin blockchain. There is no other similar datastore which is so widely distributed. There is a tradeoff between the exact number of messages and how quickly they can be embedded. But as of December 2013, it's fair to say that one bitcoin allows around 1000 such messages to be embedded, each within about 10 minutes of being sent, since a fee of 0.001 BTC is enough to get transactions confirmed quickly. This message embedding certainly has intrinsic value since it can be used to prove ownership of a document at a certain time, by including a one-way hash of that document in a transaction. Considering that electronic notarization services charge something like $10/document, this would give an intrinsic value of around $10,000 per bitcoin.

While some other tangible commodities do have intrinsic value, that value is generally much less than its trading price. Consider for example that gold, if it were not used as an inflation-proof store of value, but rather only for its industrial uses, would certainly not be worth what it is today, since the industrial requirements for gold are far smaller than the available supply thereof.

In any event, while historically intrinsic value, as well as other attributes like divisibility, fungibility, scarcity, durability, helped establish certain commodities as mediums of exchange, it is certainly not a prerequisite. While bitcoins are accused of lacking 'intrinsic value' in this sense, they make up for it in spades by possessing the other qualities necessary to make it a good medium of exchange, equal to or better than [http://en.wikipedia.org/wiki/Commodity_money commodity money].

Another way to think about this is to consider the value of bitcoin the global network, rather than each bitcoin in isolation. The value of an individual telephone is derived from the network it is connected to. If there was no phone network, a telephone would be useless. Similarly the value of an individual bitcoin derives from the global network of bitcoin-enabled merchants, exchanges, wallets, etc... Just like a phone is necessary to transmit vocal information through the network, a bitcoin is necessary to transmit economic information through the network.

Value is ultimately determined by what people are willing to trade for - by supply and demand.

== Bitcoins are illegal because they're not legal tender ==
In March 2013, the U.S. [http://en.wikipedia.org/wiki/Financial_Crimes_Enforcement_Network Financial Crimes Enforcement Network] issues a new set of guidelines on "de-centralized virtual currency", clearly targeting Bitcoin. Under the new guidelines, "a user of virtual currency is not a Money Services Businesses (MSB) under FinCEN's regulations and therefore is not subject to MSB registration, reporting, and record keeping regulations." <ref>[http://arstechnica.com/tech-policy/2013/03/us-regulator-bitcoin-exchanges-must-comply-with-money-laundering-laws/ US regulator: Bitcoin exchanges must comply with money-laundering laws | Ars Technica]</ref> [[Mining|Miners]], when mining bitcoins for their own personal use, aren't required to register as a MSB or Money Transmitter. <ref>[http://fincen.gov/news_room/rp/rulings/html/FIN-2014-R001.html Application of FinCEN’s Regulations to Virtual Currency Mining Operations | Fincen]</ref>

In general, there are a [http://en.wikipedia.org/wiki/Local_currency number of currencies] in existence that are not official government-backed currencies. A currency is, after all, nothing more than a convenient unit of account. While national laws may vary from country to country, and you should certainly check the laws of your jurisdiction, in general trading in any commodity, including digital currency like Bitcoin, [http://en.wikipedia.org/wiki/BerkShares BerkShares], game currencies like WoW gold, or Linden dollars, is not illegal.

== Bitcoin is a form of domestic terrorism because it only harms the economic stability of the USA and its currency ==

According to [http://en.wikipedia.org/wiki/Definitions_of_terrorism#United_States the definition of terrorism in the United States], you need to do violent activities to be considered a terrorist for legal purposes. Recent off-the-cuff remarks by politicians have no basis in law or fact.

Also, Bitcoin isn't domestic to the US or any other country. It's a worldwide community, as can be seen in this [https://bitcointalk.org/?topic=2346.0 map of Bitcoin nodes].

== Bitcoin will only enable tax evaders which will lead to the eventual downfall of civilization ==

Cash transactions hold the same level of anonymity but are still taxed successfully. It is up to you to follow the applicable state laws in your home country, or face the consequences.

While it may be easy to transfer bitcoins anonymously, ''spending'' them anonymously on tangibles is just as hard as spending any other kind of money anonymously. Tax evaders are often caught because their lifestyle and assets are inconsistent with their reported income, and not necessarily because government is able to follow their money.

== Bitcoins can be printed/minted by anyone and are therefore worthless ==

Bitcoins are not printed/minted. Instead, [[Blocks]] are computed by miners and for their efforts they are awarded a specific amount of bitcoins and transaction fees paid by others. See [[Mining]] for more information on how this process works.

== Bitcoins are worthless because they're based on unproven cryptography ==

SHA256 and ECDSA which are used in Bitcoin are well-known industry standard algorithms. SHA256 is endorsed and used by the US Government and is standardized (FIPS180-3 Secure Hash Standard). If you believe that these algorithms are untrustworthy then you should not trust Bitcoin, credit card transactions or any type of electronic bank transfer. Bitcoin has a sound basis in well understood cryptography.

== Early adopters are unfairly rewarded ==

Early adopters are rewarded for taking the higher risk with their time and money. The capital invested in bitcoin at each stage of its life invigorated the community and helped the currency to reach subsequent milestones. Arguing that early adopters do not deserve to profit from this is akin to saying that early investors in a company, or people who buy stock at a company IPO (Initial Public Offering), are unfairly rewarded.

This argument also depends on bitcoin early adopters using bitcoins to store rather than transfer value. The daily trade on the exchanges (as of Jan 2012) indicates that smaller transactions are becoming the norm, indicating trade rather than investment. In more pragmatic terms, "fairness" is an arbitrary concept that is improbable to be agreed upon by a large population. Establishing "fairness" is no goal of Bitcoin, as this would be impossible.

Looking forwards, considering the amount of publicity bitcoin received as of April 2013, there can be no reasonable grounds for complaint for people who did not invest at that time, and then see the value (possibly) rising drastically higher.

By starting to mine or acquire bitcoins today, you too can become an early adopter.

== 21 million coins isn't enough; doesn't scale ==

One Bitcoin is divisible down to eight decimal places. There are really 2,099,999,997,690,000 (just over 2 quadrillion) maximum possible atomic units in the bitcoin system.

The value of "1 BTC" represents 100,000,000 of these. In other words, each bitcoin is divisible by up to 108.

As the value of the unit of 1 BTC grew too large to be useful for day to day transactions, people started dealing in smaller [[Units|units]], such as milli-bitcoins (mBTC) or micro-bitcoins (μBTC).

== Bitcoins are stored in wallet files, just copy the wallet file to get more coins! ==

No, your wallet contains your secret keys, giving you the rights to spend your bitcoins. Think of it like having bank details stored in a file. If you give your bank details (or bitcoin wallet) to someone else, that doesn't double the amount of money in your account. You can spend your money or they can spend your money, but not both.

== Lost coins can't be replaced and this is bad ==

Bitcoins are divisible to 0.00000001, so there being fewer bitcoins remaining is not a problem for the currency itself. If you lose your coins, all other coins will go up in value a little. Consider it a donation to all other bitcoin users.

A related question is: Why don't we have a mechanism to replace lost coins? The answer is that it is impossible to distinguish between a 'lost' coin and one that is simply sitting unused in someone's wallet.

== It's a giant ponzi scheme ==
In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. In a ponzi scheme, early adopters can only profit at the expense of late adopters, and the late adopters always lose. Bitcoin can have a win-win outcome. Earlier adopters profit from the rise in value as Bitcoin become better understood and in turn demanded by the public at large. All adopters benefit from the usefulness of a reliable and widely-accepted decentralized peer-to-peer currency.

It is also important to note that [[Satoshi Nakamoto]], creator of bitcoin, has never spent a bitcoin (other than giving them away when they were worthless) which we can verify by checking the blockchain.

== Finite coins plus lost coins means deflationary spiral ==
As deflationary forces may apply, economic factors such as hoarding are offset by human factors that may lessen the chances that a [[Deflationary spiral]] will occur.

== Bitcoin can't work because there is no way to control inflation ==

Inflation is simply a rise of prices over time, which is generally the result of the devaluing of a currency. This is a function of supply and demand. Given the fact that the supply of bitcoins is fixed at a certain amount, unlike fiat money, the only way for inflation to get out of control is for demand to disappear. Temporary inflation is possible with a rapid adoption of Fractional Reserve Banking but will stabilize once a substantial number of the 21 million "hard" bitcoins are stored as reserves by banks.

Given the fact that Bitcoin is a distributed system of currency, if demand were to decrease to almost nothing, the currency would be doomed anyway.

The key point here is that Bitcoin as a currency can't be inflated by any single person or entity, like a government, as there's no way to increase supply past a certain amount.

Indeed, the most likely scenario, as Bitcoin becomes more popular and demand increases, is for the currency to increase in value, or deflate, until demand stabilizes.

== The Bitcoin community consists of anarchist/conspiracy theorist/gold standard 'weenies' ==

The members of the community vary in their ideological stances. While it may have been started by ideological enthusiasts, Bitcoin now speaks to a large number of regular pragmatic folk, who simply see its potential for reducing the costs and friction of global e-commerce.

== Anyone with enough computing power can take over the network ==

CONFIRMED, see [[Weaknesses]].

That said, as the network grows, it becomes harder and harder for a single entity to do so. Already the Bitcoin network's computing power is quite ahead of the world's fastest supercomputers, together.

What an attacker can do once the network is taken over is quite limited. Under no circumstances could an attacker create counterfeit coins, fake transactions, or take anybody else's money. An attacker's capabilities are limited to taking back their own money that they very recently spent, and preventing other people's transactions from receiving confirmations. Such an attack would be very costly in resources, and for such meager benefits there is little rational economic incentive to do such a thing.

Furthermore, this attack scenario would only be feasible for as long as it was actively underway. As soon as the attack stopped, the network would resume normal operation.

== Bitcoin violates governmental regulations ==

There is no known governmental regulation which disallows the use of Bitcoin.

See also: the "[[#Bitcoins_are_illegal_because_they.27re_not_legal_tender|Bitcoins are illegal because they're not legal tender]]" myth.

== Fractional reserve banking is not possible ==

It is possible. See the main article, [[Fractional Reserve Banking and Bitcoin]]

== After 21 million coins are mined, no one will generate new blocks ==

When operating costs can't be covered by the block creation bounty, which will happen some time before the total amount of BTC is reached, miners will earn some profit from [[transaction fees]]. However unlike the block reward, there is [http://bitcoin.stackexchange.com/questions/876/how-much-will-transaction-fees-eventually-be/895#895 no coupling between transaction fees and the need for security], so there is less of a guarantee that the amount of [[Mining|mining]] being performed will be sufficient to maintain the network's security.

== Bitcoin has no built-in chargeback mechanism, and this isn't good ==

'''Why some people think this is bad''': Chargebacks are useful for limiting fraud. The person handling your money has a responsibility to prevent fraud. If you buy something on eBay and the seller never ships it, PayPal takes funds from the seller's account and gives you back the money. This strengthens the eBay economy, because people recognize that their risk is limited and are more willing to purchase items from risky sellers.

'''Why it's actually a good thing''': Bitcoin is designed such that your money is yours and yours alone. Allowing chargebacks implies that it is possible for another entity to take your money from you. You can have either total ownership rights of your money, or fraud protection, but not both. That said, nothing inherent in the dollar or euro or any other currency is necessary for chargebacks to be possible, and likewise, nothing prevents the creation of PayPal-like services denominated in Bitcoin that provide chargebacks or fraud protection.

The statement "The person handling your money has a responsibility to prevent fraud" is still true; the power has been shifted into your own hands. Fraud will always exist. It's up to you to only send bitcoins to trusted entities. It is possible to trust an online identity without ever knowing their physical identity; see the [http://wiki.bitcoin-otc.com/wiki/OTC_Rating_System OTC Web of Trust].

== Quantum computers would break Bitcoin's security ==

While ECDSA is indeed not secure under quantum computing, quantum computers don't yet exist and probably won't for a while.
The DWAVE system often written about in the press is, even if all their claims are true, not a quantum computer of a kind that could be used for cryptography.
Bitcoin's security, when used properly with a new address on each transaction, depends on more than just ECDSA: Cryptographic hashes are much stronger than ECDSA under QC.
Bitcoin's security was designed to be upgraded in a forward compatible way and could be [http://en.wikipedia.org/wiki/Post-quantum_cryptography upgraded] if this were considered an imminent threat.

See the implications of quantum computers on public key cryptography here http://en.wikipedia.org/wiki/Quantum_computer#Potential

The ''risk'' of quantum computers is also there for financial institutions, like banks, because they heavily rely on cryptography when doing transactions.

== Bitcoin makes self-sufficient artificial intelligence possible ==
[[StorJ]]<ref>[http://garzikrants.blogspot.com/2013/01/storj-and-bitcoin-autonomous-agents.html StorJ And Bitcoin Autonomous Agents]</ref>, a theorized autonomous agent which utilizes humans to build itself and issues autonomous payments for improvement work done, is not a conscious entity. Whatever AI is possible, is not going to be magically more possible simply because it could incentivize human behaviour with pseudonymous Bitcoin payments.

== [[Mining|Bitcoin mining]] is a waste of energy and harmful for ecology ==
No more so than the wastefulness of mining gold out of the ground, melting it down and shaping it into bars, and then putting it back underground again. Not to mention the building of big fancy buildings, the waste of energy printing and minting all the various fiat currencies, the transportation thereof in armored cars by no less than two security guards for each who could probably be doing something more productive, etc.

As far as mediums of exchange go, Bitcoin is actually quite economical of resources, compared to others.

'''Economic Argument 1'''

[[Mining|Bitcoin mining]] is a highly competitive, dynamic, almost [http://en.wikipedia.org/wiki/Perfect_market perfect], market. Mining rigs can be set up and dismantled almost anywhere in the world with relative ease. Thus, market forces are constantly pushing mining activity to ''places'' and ''times'' where the marginal price of electricity is low or zero. These electricity products are cheap for a reason. Often it’s because the electricity is difficult (and wasteful) to transport, difficult to store, or because there is low demand and high supply. Using electricity in this way is a lot less wasteful than simply plugging a mining rig into the mains indiscriminately.

For example, Iceland produces an excess of cheap electricity from renewable sources, but it has no way of exporting electricity because of its remote location. It is conceivable that at some point in future Bitcoin mining will only be profitable in places like Iceland, and unprofitable in places like central Europe, where electricity comes mostly from nuclear and fossil sources.

Market forces could even push mining into innovative solutions that have an effective electricity consumption of ''zero''. Mining always produces heat equivalent to the energy consumed - for example, 1000 watts of mining equipment produces the same amount of heat as a 1000 watt heating element used in an electric space heater, hot tub, water heater, or similar appliance. Someone already in a willing position to incur the cost of electricity for its heat value alone could run mining equipment specially designed to mine bitcoins while capturing and utilizing the heat produced, without incurring any energy costs beyond what they already intended to spend on heating.

(Note that this is just an example; mining will not always produce heat equivalent to the energy consumed because some energy is inevitably released as electromagnetic radiation, among others.)

'''Economic Argument 2'''

When the environmental costs of mining are considered, they need to be weighed up against the benefits. If you question Bitcoin on the grounds that it consumes electricity, then you should also ask questions like this: Will Bitcoin promote economic growth by freeing up trade? Will this speed up the rate of technological innovation? Will this lead to faster development of green technologies? Will Bitcoin enable new, border crossing [http://en.wikipedia.org/wiki/Smart_grid smart grid] technologies? …

Dismissal of Bitcoin because of its costs, while ignoring its benefits, is a dishonest argument. In fact, any environmental argument of this type is dishonest, not just pertaining to Bitcoin. Along similar lines, it could be argued that wind turbines are bad for the environment because making the steel structure consumes energy.

'''Ratio of Capital Costs versus Electrical Costs'''

The BFL Jalapeno hashes at 5.5 Gh/s using 30W. That device consumes about $40 per year in electricity (using U.S. residential average of about $0.15 per kWh.) But the device costs over $300 including shipping. Thus just about a quarter of all costs over a two-year useful life goes to electricity. This compares to GPUs where more than 90% of costs over a two-year life went to electricity. Even more efficient designs can be expected in the future.

== Shopkeepers can't seriously set prices in bitcoins because of the volatile exchange rate ==

The assumption is that bitcoins must be sold immediately to cover operating expenses. If the shopkeeper's back-end expenses were transacted in bitcoins as well, then the exchange rate would be irrelevant. Larger adoption of Bitcoin would make prices [http://en.wikipedia.org/wiki/Sticky_%28economics%29 sticky]. Future volatility is expected to decrease, as the size and depth of the market grows.

In the meantime, many merchants simply regularly pull the latest market rates from the exchanges and automatically update the prices on their websites. Also you might be able to buy a put option in order to sell at a fixed rate for a given amount of time. This would protect you from drops in price and simplify your operations for that time period.

== Like Flooz and e-gold, bitcoins serve as opportunities for criminals and will be shut down ==

* Visa, MasterCard, PayPal, and cash all serve as opportunities for criminals as well, but society keeps them around due to their recognized net benefit.
* Hopefully Bitcoin will grow to the point where no single organization can disrupt the network, or would be better served by helping it.
* Terrorists fly aircraft into buildings, but the governments have not yet abolished consumer air travel. Obviously the public good outweighs the possible bad in their opinion.
* Criminal law differs between jurisdictions.

== Bitcoins will be shut down by the government just like Liberty Dollars were ==

Liberty Dollars started as a commercial venture to establish an alternative US currency, including physical banknotes and coins, backed by precious metals. This, in and of itself, is not illegal. They were prosecuted under counterfeiting laws because the silver coins allegedly resembled US currency.

Bitcoins do not resemble the currency of the US or of any other nation in any way, shape, or form. The word "dollar" is not attached to them in any way. The "$" symbol is not used in any way.

Bitcoins have no representational similarity whatsoever to US dollars.

Of course, actually 'shutting down' Liberty Dollars was as easy as arresting the head of the company and seizing the offices and the precious metals used as backing. The decentralized Bitcoin, with no leader, no servers, no office, and no tangible asset backing, does not have the same vulnerability.

== Bitcoin is not decentralized because the developers can dictate the software's behavior ==

The Bitcoin protocol was originally defined by Bitcoin's inventor, [[Satoshi Nakamoto]], and this protocol has now been widely accepted as the standard by the community of miners and users.

Though the developers of the original Bitcoin client still exert influence over the Bitcoin community, their power to arbitrarily modify the protocol is very limited. Since the release of Bitcoin v0.3, changes to the protocol have been minor and always in agreement with community consensus.

Protocol modifications, such as increasing the block award from 25 to 50 BTC, are not compatible with clients already running in the network. If the developers were to release a new client that the majority of miners perceives as corrupt, or in violation of the project’s aims, that client would simply not catch on, and the few users who do try to use it would find that their transactions get rejected by the network.

There are also other [[:Category:Clients|Bitcoin clients made by other developers]] that adhere to the Bitcoin protocol. As more developers create alternative clients, less power will lie with the developers of the original Bitcoin client.

== Bitcoin is a pyramid scheme ==

Bitcoin is nearly opposite of a pyramid scheme in a mathematical sense. Because Bitcoins are algorithmically made scarce, no exponential benefit is derived from introducing new users to use of it. There is a quantitative benefit in having additional interest or demand, but this is in no way exponential.

== Bitcoin was hacked ==

In the history of Bitcoin, there has never been an attack on the [[block chain]] that resulted in stolen money from a confirmed output. Neither has there ever been a reported theft resulting directly from a vulnerability in the [[Original Bitcoin client|original Bitcoin client]], or a vulnerability in the protocol. Bitcoin is secured by standard cryptographic functions. These functions have been peer reviewed by cryptography experts and are considered unlikely to be breakable in the foreseeable future.

It is safe to say that the currency itself has never been 'hacked'. However, several major ''websites'' using the currency have been hacked, often resulting in high profile Bitcoin heists. These heists are misreported in some media as hacks on Bitcoin itself. An analogy: Just because someone stole US dollars from a supermarket till, doesn’t mean that the US dollar as a currency has been 'hacked'.

Most bitcoin thefts are the result of inadequate [[Securing your wallet|wallet security]]. In response to the wave of thefts in 2011 and 2012, the community has developed risk-mitigating measures such as [[Wallet_encryption|wallet encryption]], support for [[BIP_0011|multiple signatures]], [[How_to_set_up_a_secure_offline_savings_wallet|offline wallets]], [[Paper_wallet|paper wallets]], and [[Hardware_wallet|hardware wallets]]. As these measures gain adoption by merchants and users, the number of thefts drop.

==References==
<references/>

[[de:Mythen]]
[[ru:Мифы о биткоине]]

Category:Mining contractors

2014-10-10T19:23:02Z

Atheros: moved Midnightmagic's text to this page where it is appropriate.

Provides mining services with performance specified by contract. For example, a specific level of mining capacity may be rented out for a set price for a specific duration. Mining shares provide Mining as a Service (MaaS). These break large-scale datacenter mining down to easily manageable pieces that are available in the form of shares of equipment.

Hosted mining services and Cloud Mining create systemic risk for Bitcoin because they undermine the security assumption that the control of mining power is well-distributed. If too much hashrate is consolidated in large hosting centres, an attacker is more-easily able to compromise a significant portion of it and could potentially disrupt Bitcoin or steal back their own spent money.

[[Category:Mining]]

Mining

2014-10-10T19:19:06Z

Atheros: Undo revision 51070 by Midnightmagic (talk) It is important but not appropriate here. That should go on the Mining contractors page and not here. This is only an introduction article.

[[File:Quick-and-dirty-4x5970-cooling.jpg|thumb|right|A quick and dirty mining rig]]
== Introduction ==
'''Mining''' is the process of adding transaction records to Bitcoin's public ledger of past transactions.
This ledger of past transactions is called the [[block chain]] as it is a chain of [[block|blocks]].
The block chain serves to [[Confirmation|confirm]] transactions to the rest of the network as having taken place.
Bitcoin nodes use the block chain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.

Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual [[blocks]] must contain a [[proof of work|proof of work]] to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the [[hashcash]] proof-of-work function.

The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus.
Mining is also the mechanism used to introduce Bitcoins into the system:
Miners are paid any transaction fees as well as a "subsidy" of newly created coins.
This both serves the purpose of disseminating new coins in a decentralized manner as well as motivating people to provide security for the system.

Bitcoin mining is so called because it resembles the mining of other commodities:
it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.

== Difficulty ==
=== The Computationally-Difficult Problem ===
Mining a block is difficult because the SHA-256 hash of a block's header must be lower than or equal to the [[Target|target]] in order for the block to be accepted by the network. This problem can be simplified for explanation purposes: The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a [[Nonce|nonce]] is incremented. See [[Proof of work]] for more information.

=== The Difficulty Metric ===
The [[Difficulty|difficulty]] is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every 2016 blocks to a value such that the previous 2016 blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes. As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty [[Target|target]] will simply be rejected by everyone on the network and thus will be worthless.

=== Reward ===
When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks. See [[Controlled Currency Supply]].

Additionally, the miner is awarded the fees paid by users sending transactions. The fee is an incentive for the miner to include the transaction in their block. In the future, as the number of new bitcoins miners are allowed to create in each block dwindles, the fees will make up a much more important percentage of mining income.

== The mining ecosystem ==

=== Hardware ===
[[File:Usb-fpga module 1.15x-hs-800.jpg|thumb|right|FPGA Module]]
Users have used various types of hardware over time to mine blocks. Hardware specifications and performance statistics are detailed on the [[Mining Hardware Comparison]] page.
==== CPU Mining ====
Early Bitcoin client versions allowed users to use their CPUs to mine. The advent of GPU mining made CPU mining financially unwise as the hashrate of the network grew to such a degree that the amount of bitcoins produced by CPU mining became lower than the cost of power to operate a CPU. The option was therefore removed from the core Bitcoin client's user interface.

==== GPU Mining ====
GPU Mining is drastically faster and more efficient than CPU mining. See the main article: [[Why a GPU mines faster than a CPU]]. A variety of popular [[Mining rig|mining rigs]] have been documented.
==== FPGA Mining ====
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. See [[Mining Hardware Comparison]] for FPGA hardware specifications and statistics.
==== ASIC Mining ====
An application-specific integrated circuit, or ''ASIC'', is a microchip designed and manufactured for a very specific purpose. ASICs designed for Bitcoin mining were first released in 2013. For the amount of power they consume, they are vastly faster than all previous technologies and already have made GPU mining financially unwise in some countries and setups.

==== Mining services (Cloud mining) ====
[[:Category:Mining_contractors|Mining contractors]] provide mining services with performance specified by contract, often referred to as a "Mining Contract". They may, for example, rent out a specific level of mining capacity for a set price for a specific duration.

=== Pools ===
As more and more miners competed for the limited supply of blocks, individuals found that they were working for months without finding a block and receiving any reward for their mining efforts. This made mining something of a gamble. To address the variance in their income miners started organizing themselves into [[Pooled mining|pools]] so that they could share rewards more evenly. See [[Pooled mining]] and [[Comparison of mining pools]].

=== History ===
Bitcoin's public ledger (the 'block chain') was started on January 3rd, 2009 at 18:15 UTC presumably by [[Satoshi Nakamoto]]. The first block is known as the [[genesis block]]. The first transaction recorded in the first block was a single transaction paying the reward of 50 new bitcoins to its creator.

==See Also==

* [http://BitcoinMiner.net Comprehensive Guide Bitcoin Miner and Mining]
* [http://codinginmysleep.com/bitcoin-mining-in-plain-english Bitcoin Mining in Plain English] by David Perry
* [[Automatically mine when computer is locked|Tutorial to automatically start mining when you lock your computer]]. (Windows 7)
* [http://www.reddit.com/r/Bitcoin/comments/18q2jx/eli5_bitcoin_mining_xpost_in_eli5/ Simplified Explanation of Bitcoin Mining] by reddit user [http://www.reddit.com/user/azotic azotic]
* [http://www.vnbitcoin.org/bitcoincalculator.php Bitcoin Mining Calculator]
* [http://www.MiningContracts.com Research, Review and Compare Cloud Mining Contracts]
[[ru:Mining]]
[[Category:Mining]][[Category:Vocabulary]]

File talk:Total bitcoins over time graph.png

2014-10-10T19:04:22Z

Atheros:

==Removing This Stupid Graph==

I have removed all links to this file. Please do not put them back. This graph has convinced people that the last mined reward will be in 2033 or so, when that is completely incorrect. Thanks. [[User:Midnightmagic|Midnightmagic]] ([[User talk:Midnightmagic|talk]]) 01:54, 12 January 2014 (GMT)
: What I wouldn't delete out of reflex because of the huge amount of PR and fact-correction I've personally been forced to do as a result of this stupid thing, would be a graph which shows a comparison line that describes compression of the release schedule due to hashrate growth so far, as well as reasonably expected growth into the 2100s. Ideally, events such as 'last Satoshi mined' and "if past growth continues, here is where we will be using the entire energy output of the Earth to sustain bitcoin mining" should be notated with an arrow, and the volume line should '''not''' abruptly end at any point prior. [[User:Midnightmagic|Midnightmagic]] ([[User talk:Midnightmagic|talk]]) 07:07, 14 September 2014 (UTC)

We should re-add a similar graph. It makes sense that people would think that the reward would stop increasing after 2033 based on that graph, which is incorrect, but that graph also helps people understand the exponential back-off nature of the reward. It is valuable. I believe that it has done more good than harm and I haven't seen it declared anywhere myself that no more bitcoins will be mined after 2033 unless people are just speaking 'practically'. By the way, if over 99% of bitcoins have been mined by 2033 then for many contexts, like economics, *practically* no more bitcoins are being mined. So in the context of economics and other fields, it is correct to say that no more bitcoins will be mined after 2033.

Separately, the lack of a comparison line that describes the compression of the release schedule due to hashrate growth so far is not sufficient reason to get rid of this graph. When educating the public, sometimes details can be ignored for the purposes of explanation. Demanding that the line be a couple pixels to the left is definitely one of those details that can be ignored. This is evidence that, in deleting this graph, you are behaving like a pedant. Please stop. [[User:Atheros|Atheros]] ([[User talk:Atheros|talk]]) 19:04, 10 October 2014 (UTC)

Fractional Reserve Banking and Bitcoin

2014-09-12T22:13:07Z

Atheros: Gox is dead.

While Fractional Reserve Banking with Bitcoin is possible and already implemented with [https://coinlenders.com CoinLenders], there is [https://bitcointalk.org/index.php?topic=51899.0 disagreement] over what it would entail. Much discussion occurred on the [[Talk:Myths#Fractional_reserve_banking_with_Bitcoin_is_fundamentally_different|Myths Talk Page]].

==Keynesian Viewpoint==
Fractional Reserve Banking with Bitcoin is possible and practical. There is no fundamental difference between classical currencies and Bitcoin as it applies to banking. Banks will still be free to take in bitcoins and present them to customers as "available for withdrawal" while still lending most of those bitcoins to a different customer for a profit. Some of those bitcoins will be held in reserves in case of a bank run. It will be up to the bank to hold a sufficient supply of reserves in order to prevent insolvency in the event of a bank run. Central banks were established to enforce reserve requirements and so, with Bitcoin lacking a central bank, some banks will almost surely collapse, taking their customers' deposits with them. A large bitcoin exchange could tomorrow lend out 10,000 bitcoins to an individual to start a business. The [http://www.federalreserve.gov/faqs/money_12845.htm money supply] would thus increase by 10,000 and we would instantly have Fractional Reserve Banking. The same amount of bitcoins would still exist in the [[Block Chain]], but the body of people participating in the Bitcoin economy would have the perception that more bitcoins exist. If the value of a bitcoin is stable for a long period of time, then Fractional Reserve Banking is ''inevitable''. 

See [http://en.wikipedia.org/wiki/Fractional-reserve_banking Fractional reserve banking].

The Monetary Base of Bitcoin is limited to 21 million. But because Fractional Reserve Banking is possible, the money supply of bitcoins (which includes demand deposits) can exceed 21 million by a factor of x where x is the [http://en.wikipedia.org/wiki/Money_multiplier Money Multiplier].

==Austrian Viewpoint==

According to the [http://wiki.mises.org/wiki/Fractional_reserve_banking Austrian viewpoint]:
<blockquote>Fractional-reserve banking (or FRB) is the widespread banking practice in which only a fraction of a bank's demand deposits are kept in reserve and available for immediate withdrawal (as cash and other highly liquid assets), whilst the remaining cash is lent out to borrowers (and so is never actually available for immediate withdrawal to legitimate deposit-holders).</blockquote>

In order for fractional reserve banking to affect the money supply, the debt instruments issued by the bank (for example, bank notes or demand deposits) must be accepted as if they were money proper, in other words, they must be money-substitutes. This is explained for example by [http://mises.org/rothbard/austrianmoneysupply.pdf Rothbard in Austrian Definitions of the Supply of Money]:

<blockquote>And so long as demand deposits are accepted as equivalent to standard money, they will function as part of the money supply.

It is important to recognize that demand deposits are not automatically part of the money supply by virtue of their very existence; they continue as equivalent to money only so long as the subjective estimates of the sellers of goods on the market think that they are so equivalent and accept them as such in exchange.</blockquote>

In the historical cases of money based on gold or government issued fiat, the reason why money-substitutes are accepted as if they were money proper is that the money proper has in some circumstances high transaction costs (for example, gold might be too heavy to carry around, or the buyer and seller are not at the same location and want to perform the exchange electronically), or are not legally permitted (normal people are not allowed to obtain central bank reserves). This creates a demand for forms of money which have lower transaction costs. With gold/fiat, this requires the creation of debt instruments, which then, after being generally accepted in exchange, become money substitutes and a part of the money supply.

The situation with Bitcoin is different, because other forms can be created without debt instruments, for example [[Casascius physical bitcoins]] or [[Bitbills]]. Bitcoin in its "classical" form is similar in function of a bank account (allowing electronic transfers of balances) even though there is no debt instrument. Any object that can store 64 bytes of data (size of Bitcoin keypair) can, hypothetically, be used as a form of Bitcoin. In some cases, shorter forms than 64 bytes are possible too (for example, [[Mini_private_key_format|mini private key format]] used by Casascius physical bitcoins). Issuers of Bitcoin-based debt instruments, if they expect these instruments to be accepted in exchange, need to create demand for them as a method of payment outside of the Bitcoin network. This is difficult, because a transaction that occurs outside of the Bitcoin network is incompatible with it, so people equipped with software for handling only pure Bitcoin transactions cannot accept it. Furthermore, they also would need to compete against not only Bitcoin, but against other currencies, payment methods and services.

Currently, Bitcoin based debt instruments are restricted to a narrow field of uses. Exchanges allow these instruments to be traded against other currencies. E-wallets allow inter-wallet transfers. GLBSE allows the floating of shares or other contractual arrangements. However, these debt instruments are, in general, outside of these narrow fields, not accepted for exchange as if they were native Bitcoins. They rarely even circulate outside of the internal transactions of the providers of these services. There are very few exceptions, such as the redeemable Mt. Gox code. If the service provider attempted to conduct FRB by overissuing these instruments, they would be exposed at risk of having them redeemed too quickly. One possible way of mitigating this risk is to institute a suspension of specie payments (for example, Mt. Gox. having a default withdrawal limit).

If in the future, P2P exchanges and distributed wallets are available (both have been suggested already at bitcointalk.org forums), this would decrease the demand for Bitcoin-based debt instruments even further.

Historically, in all known situations where an overissue of Bitcoin-based debt instruments was produced, this resulted either in a voluntary elimination of the excess instruments (Mt. Gox hack from June 2011), bankruptcy (the demise of mybitcoin) or a new investor bailout (the demise of bitomat.pl and subsequent takeover by Mt. Gox). Here we have empirical evidence that FRB with Bitcoin is possible.

Putting all this together, there are several steps that need to be addressed regarding Bitcoin-FRB and money supply:

# overissue of debt instruments (this would cause FRB)
# general acceptance of these instruments as a method of payment (this would mean the instruments need to be included in the money supply)
# market price of these instruments at a different rate than the reserve ratio of the issuer (this would cause inflation or deflation)

Even if we assume that an overissue is possible in long term, there are significant obstacles in phase 2 and 3, as elaborated above. It is therefore unlikely that even if Bitcoin-FRB became widespread, this would significantly affect the money supply of Bitcoins or inflation/deflation.
[[Category:Economics]]

Myths

2014-09-12T22:00:02Z

Atheros: A myth is defined as "a widely held but false belief or idea." If a belief isn't widely held by some group of otherwise rational people then it doesn't belong here.

Let's clear up some common Bitcoin misconceptions.

== Bitcoin is just like all other digital currencies; nothing new ==

Nearly all other digital currencies are centrally controlled. This means that:
* They can be printed at the subjective whims of the controllers
* They can be destroyed by attacking the central point of control
* Arbitrary rules can be imposed upon their users by the controllers

Being decentralized, Bitcoin solves all of these problems.

== Bitcoins don't solve any problems that fiat currency and/or gold doesn't solve ==

Unlike gold, bitcoins are:
* Easy to transfer
* Easy to secure
* Easy to verify
* Easy to granulate

Unlike fiat currencies, bitcoins are:
* Predictable and limited in [[Controlled_Currency_Supply|supply]]
* Not controlled by a central authority (such as [http://en.wikipedia.org/wiki/Federal_Reserve The United States Federal Reserve])
* Not debt-based

Unlike electronic fiat currency systems, bitcoins are:
* Potentially anonymous
* Freeze-proof
* Faster to transfer
* Cheaper to transfer

== Bitcoin is backed by processing power ==

It is not correct to say that Bitcoin is "backed by" processing power. A currency being "backed" means that it is pegged to something else via a central party at a certain exchange rate yet you cannot exchange bitcoins for the computing power that was used to create them. Bitcoin is in this sense not backed by anything. It is a currency in its own right. Just as gold is not backed by anything, the same applies to Bitcoin.

The Bitcoin currency is ''created'' via processing power, and the integrity of the block chain is ''protected'' by the existence of a network of powerful computing nodes from certain [[Weaknesses#Attacker_has_a_lot_of_computing_power|attacks]].

== Bitcoins are worthless because they aren't backed by anything ==

One could argue that gold isn't backed by anything either. Bitcoins have properties resulting from the system's design that allows them to be subjectively valued by individuals. This valuation is demonstrated when individuals freely exchange for or with bitcoins. Please refer to the [http://en.wikipedia.org/wiki/Subjective_theory_of_value Subjective Theory of Value].

See also: the "[[#Bitcoin_is_backed_by_processing_power|Bitcoin is backed by processing power]]" myth.

== The value of bitcoins are based on how much electricity and computing power it takes to mine them ==

This statement is an attempt to apply to Bitcoin the [http://en.wikipedia.org/wiki/Labor_theory_of_value labor theory of value], which is generally accepted as false. Just because something takes X resources to create does not mean that the resulting product will be worth X. It can be worth more, or less, depending on the utility thereof to its users.

In fact the causality is the reverse of that (this applies to the labor theory of value in general). The cost to mine bitcoins is based on how much they are worth. If bitcoins go up in value, more people will mine (because [[Mining|mining]] is profitable), thus [[difficulty]] will go up, thus the cost of mining will go up. The inverse happens if bitcoins go down in value. These effects balance out to cause mining to always cost an amount proportional to the value of bitcoins it produces.

== Bitcoins have no intrinsic value (unlike some other things) ==

This is simply not true. Each bitcoin gives the holder the ability to embed a large number of short in-transaction messages in a globally distributed and timestamped permanent data store, namely the bitcoin blockchain. There is no other similar datastore which is so widely distributed. There is a tradeoff between the exact number of messages and how quickly they can be embedded. But as of December 2013, it's fair to say that one bitcoin allows around 1000 such messages to be embedded, each within about 10 minutes of being sent, since a fee of 0.001 BTC is enough to get transactions confirmed quickly. This message embedding certainly has intrinsic value since it can be used to prove ownership of a document at a certain time, by including a one-way hash of that document in a transaction. Considering that electronic notarization services charge something like $10/document, this would give an intrinsic value of around $10,000 per bitcoin.

While some other tangible commodities do have intrinsic value, that value is generally much less than its trading price. Consider for example that gold, if it were not used as an inflation-proof store of value, but rather only for its industrial uses, would certainly not be worth what it is today, since the industrial requirements for gold are far smaller than the available supply thereof.

In any event, while historically intrinsic value, as well as other attributes like divisibility, fungibility, scarcity, durability, helped establish certain commodities as mediums of exchange, it is certainly not a prerequisite. While bitcoins are accused of lacking 'intrinsic value' in this sense, they make up for it in spades by possessing the other qualities necessary to make it a good medium of exchange, equal to or better than [http://en.wikipedia.org/wiki/Commodity_money commodity money].

Another way to think about this is to consider the value of bitcoin the global network, rather than each bitcoin in isolation. The value of an individual telephone is derived from the network it is connected to. If there was no phone network, a telephone would be useless. Similarly the value of an individual bitcoin derives from the global network of bitcoin-enabled merchants, exchanges, wallets, etc... Just like a phone is necessary to transmit vocal information through the network, a bitcoin is necessary to transmit economic information through the network.

Value is ultimately determined by what people are willing to trade for - by supply and demand.

== Bitcoins are illegal because they're not legal tender ==
In March 2013, the U.S. [http://en.wikipedia.org/wiki/Financial_Crimes_Enforcement_Network Financial Crimes Enforcement Network] issues a new set of guidelines on "de-centralized virtual currency", clearly targeting Bitcoin. Under the new guidelines, "a user of virtual currency is not a Money Services Businesses (MSB) under FinCEN's regulations and therefore is not subject to MSB registration, reporting, and record keeping regulations." <ref>[http://arstechnica.com/tech-policy/2013/03/us-regulator-bitcoin-exchanges-must-comply-with-money-laundering-laws/ US regulator: Bitcoin exchanges must comply with money-laundering laws | Ars Technica]</ref> [[Mining|Miners]], when mining bitcoins for their own personal use, aren't required to register as a MSB or Money Transmitter. <ref>[http://fincen.gov/news_room/rp/rulings/html/FIN-2014-R001.html Application of FinCEN’s Regulations to Virtual Currency Mining Operations | Fincen]</ref>

In general, there are a [http://en.wikipedia.org/wiki/Local_currency number of currencies] in existence that are not official government-backed currencies. A currency is, after all, nothing more than a convenient unit of account. While national laws may vary from country to country, and you should certainly check the laws of your jurisdiction, in general trading in any commodity, including digital currency like Bitcoin, [http://en.wikipedia.org/wiki/BerkShares BerkShares], game currencies like WoW gold, or Linden dollars, is not illegal.

== Bitcoin is a form of domestic terrorism because it only harms the economic stability of the USA and its currency ==

According to [http://en.wikipedia.org/wiki/Definitions_of_terrorism#United_States the definition of terrorism in the United States], you need to do violent activities to be considered a terrorist for legal purposes. Recent off-the-cuff remarks by politicians have no basis in law or fact.

Also, Bitcoin isn't domestic to the US or any other country. It's a worldwide community, as can be seen in this [https://bitcointalk.org/?topic=2346.0 map of Bitcoin nodes].

== Bitcoin will only enable tax evaders which will lead to the eventual downfall of civilization ==

Cash transactions hold the same level of anonymity but are still taxed successfully. It is up to you to follow the applicable state laws in your home country, or face the consequences.

While it may be easy to transfer bitcoins anonymously, ''spending'' them anonymously on tangibles is just as hard as spending any other kind of money anonymously. Tax evaders are often caught because their lifestyle and assets are inconsistent with their reported income, and not necessarily because government is able to follow their money.

== Bitcoins can be printed/minted by anyone and are therefore worthless ==

Bitcoins are not printed/minted. Instead, [[Blocks]] are computed by miners and for their efforts they are awarded a specific amount of bitcoins and transaction fees paid by others. See [[Mining]] for more information on how this process works.

== Bitcoins are worthless because they're based on unproven cryptography ==

SHA256 and ECDSA which are used in Bitcoin are well-known industry standard algorithms. SHA256 is endorsed and used by the US Government and is standardized (FIPS180-3 Secure Hash Standard). If you believe that these algorithms are untrustworthy then you should not trust Bitcoin, credit card transactions or any type of electronic bank transfer. Bitcoin has a sound basis in well understood cryptography.

== Early adopters are unfairly rewarded ==

Early adopters are rewarded for taking the higher risk with their time and money. The capital invested in bitcoin at each stage of its life invigorated the community and helped the currency to reach subsequent milestones. Arguing that early adopters do not deserve to profit from this is akin to saying that early investors in a company, or people who buy stock at a company IPO (Initial Public Offering), are unfairly rewarded.

This argument also depends on bitcoin early adopters using bitcoins to store rather than transfer value. The daily trade on the exchanges (as of Jan 2012) indicates that smaller transactions are becoming the norm, indicating trade rather than investment. In more pragmatic terms, "fairness" is an arbitrary concept that is improbable to be agreed upon by a large population. Establishing "fairness" is no goal of Bitcoin, as this would be impossible.

Looking forwards, considering the amount of publicity bitcoin received as of April 2013, there can be no reasonable grounds for complaint for people who did not invest at that time, and then see the value (possibly) rising drastically higher.

By starting to mine or acquire bitcoins today, you too can become an early adopter.

== 21 million coins isn't enough; doesn't scale ==

One Bitcoin is divisible down to eight decimal places. There are really 2,099,999,997,690,000 (just over 2 quadrillion) maximum possible atomic units in the bitcoin system.

The value of "1 BTC" represents 100,000,000 of these. In other words, each is divisible by up to 10^8.

As the value of the unit of 1 BTC grows too large to be useful for day to day transactions, people can start dealing in smaller [[Units|units]], such as milli-bitcoins (mBTC) or micro-bitcoins (μBTC).

== Bitcoins are stored in wallet files, just copy the wallet file to get more coins! ==

No, your wallet contains your secret keys, giving you the rights to spend your bitcoins. Think of it like having bank details stored in a file. If you give your bank details (or bitcoin wallet) to someone else, that doesn't double the amount of money in your account. You can spend your money or they can spend your money, but not both.

== Lost coins can't be replaced and this is bad ==

Bitcoins are divisible to 0.00000001, so there being fewer bitcoins remaining is not a problem for the currency itself. If you lose your coins, all other coins will go up in value a little. Consider it a donation to all other bitcoin users.

A related question is: Why don't we have a mechanism to replace lost coins? The answer is that it is impossible to distinguish between a 'lost' coin and one that is simply sitting unused in someone's wallet.

== It's a giant ponzi scheme ==
In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. In a ponzi scheme, early adopters can only profit at the expense of late adopters, and the late adopters always lose. Bitcoin has an expected win-win outcome. Early and present adopters profit from the rise in value as Bitcoins become better understood and in turn demanded by the public at large. All adopters benefit from the usefulness of a reliable and widely-accepted decentralized peer-to-peer currency.

== Finite coins plus lost coins means deflationary spiral ==
As deflationary forces may apply, economic factors such as hoarding are offset by human factors that may lessen the chances that a [[Deflationary spiral]] will occur.

== Bitcoin can't work because there is no way to control inflation ==

Inflation is simply a rise of prices over time, which is generally the result of the devaluing of a currency. This is a function of supply and demand. Given the fact that the supply of bitcoins is fixed at a certain amount, unlike fiat money, the only way for inflation to get out of control is for demand to disappear. Temporary inflation is possible with a rapid adoption of Fractional Reserve Banking but will stabilize once a substantial number of the 21 million "hard" bitcoins are stored as reserves by banks.

Given the fact that Bitcoin is a distributed system of currency, if demand were to decrease to almost nothing, the currency would be doomed anyway.

The key point here is that Bitcoin as a currency can't be inflated by any single person or entity, like a government, as there's no way to increase supply past a certain amount.

Indeed, the most likely scenario, as Bitcoin becomes more popular and demand increases, is for the currency to increase in value, or deflate, until demand stabilizes.

== The Bitcoin community consists of anarchist/conspiracy theorist/gold standard 'weenies' ==

The members of the community vary in their ideological stances. While it may have been started by ideological enthusiasts, Bitcoin now speaks to a large number of regular pragmatic folk, who simply see its potential for reducing the costs and friction of global e-commerce.

== Anyone with enough computing power can take over the network ==

CONFIRMED, see [[Weaknesses]].

That said, as the network grows, it becomes harder and harder for a single entity to do so. Already the Bitcoin network's computing power is quite ahead of the world's fastest supercomputers, together.

What an attacker can do once the network is taken over is quite limited. Under no circumstances could an attacker create counterfeit coins, fake transactions, or take anybody else's money. An attacker's capabilities are limited to taking back their own money that they very recently spent, and preventing other people's transactions from receiving confirmations. Such an attack would be very costly in resources, and for such meager benefits there is little rational economic incentive to do such a thing.

Furthermore, this attack scenario would only be feasible for as long as it was actively underway. As soon as the attack stopped, the network would resume normal operation.

== Bitcoin violates governmental regulations ==

There is no known governmental regulation which disallows the use of Bitcoin.

See also: the "[[#Bitcoins_are_illegal_because_they.27re_not_legal_tender|Bitcoins are illegal because they're not legal tender]]" myth.

== Fractional reserve banking is not possible ==

It is possible. See the main article, [[Fractional Reserve Banking and Bitcoin]]

== After 21 million coins are mined, no one will generate new blocks ==

When operating costs can't be covered by the block creation bounty, which will happen some time before the total amount of BTC is reached, miners will earn some profit from [[transaction fees]]. However unlike the block reward, there is [http://bitcoin.stackexchange.com/questions/876/how-much-will-transaction-fees-eventually-be/895#895 no coupling between transaction fees and the need for security], so there is less of a guarantee that the amount of [[Mining|mining]] being performed will be sufficient to maintain the network's security.

== Bitcoin has no built-in chargeback mechanism, and this isn't good ==

'''Why some people think this is bad''': Chargebacks are useful for limiting fraud. The person handling your money has a responsibility to prevent fraud. If you buy something on eBay and the seller never ships it, PayPal takes funds from the seller's account and gives you back the money. This strengthens the eBay economy, because people recognize that their risk is limited and are more willing to purchase items from risky sellers.

'''Why it's actually a good thing''': Bitcoin is designed such that your money is yours and yours alone. Allowing chargebacks implies that it is possible for another entity to take your money from you. You can have either total ownership rights of your money, or fraud protection, but not both. That said, nothing inherent in the dollar or euro or any other currency is necessary for chargebacks to be possible, and likewise, nothing prevents the creation of PayPal-like services denominated in Bitcoin that provide chargebacks or fraud protection.

The statement "The person handling your money has a responsibility to prevent fraud" is still true; the power has been shifted into your own hands. Fraud will always exist. It's up to you to only send bitcoins to trusted entities. It is possible to trust an online identity without ever knowing their physical identity; see the [http://wiki.bitcoin-otc.com/wiki/OTC_Rating_System OTC Web of Trust].

== Quantum computers would break Bitcoin's security ==

While ECDSA is indeed not secure under quantum computing, quantum computers don't yet exist and probably won't for a while.
The DWAVE system often written about in the press is, even if all their claims are true, not a quantum computer of a kind that could be used for cryptography.
Bitcoin's security, when used properly with a new address on each transaction, depends on more than just ECDSA: Cryptographic hashes are much stronger than ECDSA under QC.
Bitcoin's security was designed to be upgraded in a forward compatible way and could be [http://en.wikipedia.org/wiki/Post-quantum_cryptography upgraded] if this were considered an imminent threat.

See the implications of quantum computers on public key cryptography here http://en.wikipedia.org/wiki/Quantum_computer#Potential

The ''risk'' of quantum computers is also there for financial institutions, like banks, because they heavily rely on cryptography when doing transactions.

== [[Mining|Bitcoin mining]] is a waste of energy and harmful for ecology ==
No more so than the wastefulness of mining gold out of the ground, melting it down and shaping it into bars, and then putting it back underground again. Not to mention the building of big fancy buildings, the waste of energy printing and minting all the various fiat currencies, the transportation thereof in armored cars by no less than two security guards for each who could probably be doing something more productive, etc.

As far as mediums of exchange go, Bitcoin is actually quite economical of resources, compared to others.

'''Economic Argument 1'''

[[Mining|Bitcoin mining]] is a highly competitive, dynamic, almost [http://en.wikipedia.org/wiki/Perfect_market perfect], market. Mining rigs can be set up and dismantled almost anywhere in the world with relative ease. Thus, market forces are constantly pushing mining activity to ''places'' and ''times'' where the marginal price of electricity is low or zero. These electricity products are cheap for a reason. Often it’s because the electricity is difficult (and wasteful) to transport, difficult to store, or because there is low demand and high supply. Using electricity in this way is a lot less wasteful than simply plugging a mining rig into the mains indiscriminately.

For example, Iceland produces an excess of cheap electricity from renewable sources, but it has no way of exporting electricity because of its remote location. It is conceivable that at some point in future Bitcoin mining will only be profitable in places like Iceland, and unprofitable in places like central Europe, where electricity comes mostly from nuclear and fossil sources.

Market forces could even push mining into innovative solutions that have an effective electricity consumption of ''zero''. Mining always produces heat equivalent to the energy consumed - for example, 1000 watts of mining equipment produces the same amount of heat as a 1000 watt heating element used in an electric space heater, hot tub, water heater, or similar appliance. Someone already in a willing position to incur the cost of electricity for its heat value alone could run mining equipment specially designed to mine bitcoins while capturing and utilizing the heat produced, without incurring any energy costs beyond what they already intended to spend on heating.

(Note that this is just an example; mining will not always produce heat equivalent to the energy consumed because some energy is inevitably released as electromagnetic radiation, among others.)

'''Economic Argument 2'''

When the environmental costs of mining are considered, they need to be weighed up against the benefits. If you question Bitcoin on the grounds that it consumes electricity, then you should also ask questions like this: Will Bitcoin promote economic growth by freeing up trade? Will this speed up the rate of technological innovation? Will this lead to faster development of green technologies? Will Bitcoin enable new, border crossing [http://en.wikipedia.org/wiki/Smart_grid smart grid] technologies? …

Dismissal of Bitcoin because of its costs, while ignoring its benefits, is a dishonest argument. In fact, any environmental argument of this type is dishonest, not just pertaining to Bitcoin. Along similar lines, it could be argued that wind turbines are bad for the environment because making the steel structure consumes energy.

'''Ratio of Capital Costs versus Electrical Costs'''

The BFL Jalapeno hashes at 5.5 Gh/s using 30W. That device consumes about $40 per year in electricity (using U.S. residential average of about $0.15 per kWh.) But the device costs over $300 including shipping. Thus just about a quarter of all costs over a two-year useful life goes to electricity. This compares to GPUs where more than 90% of costs over a two-year life went to electricity. Even more efficient designs can be expected in the future.

== Shopkeepers can't seriously set prices in bitcoins because of the volatile exchange rate ==

The assumption is that bitcoins must be sold immediately to cover operating expenses. If the shopkeeper's back-end expenses were transacted in bitcoins as well, then the exchange rate would be irrelevant. Larger adoption of Bitcoin would make prices [http://en.wikipedia.org/wiki/Sticky_%28economics%29 sticky]. Future volatility is expected to decrease, as the size and depth of the market grows.

In the meantime, many merchants simply regularly pull the latest market rates from the exchanges and automatically update the prices on their websites. Also you might be able to buy a put option in order to sell at a fixed rate for a given amount of time. This would protect you from drops in price and simplify your operations for that time period.

== Like Flooz and e-gold, bitcoins serve as opportunities for criminals and will be shut down ==

* Visa, MasterCard, PayPal, and cash all serve as opportunities for criminals as well, but society keeps them around due to their recognized net benefit.
* Hopefully Bitcoin will grow to the point where no single organization can disrupt the network, or would be better served by helping it.
* Terrorists fly aircraft into buildings, but the governments have not yet abolished consumer air travel. Obviously the public good outweighs the possible bad in their opinion.
* Criminal law differs between jurisdictions.

== Bitcoins will be shut down by the government just like Liberty Dollars were ==

Liberty Dollars started as a commercial venture to establish an alternative US currency, including physical banknotes and coins, backed by precious metals. This, in and of itself, is not illegal. They were prosecuted under counterfeiting laws because the silver coins allegedly resembled US currency.

Bitcoins do not resemble the currency of the US or of any other nation in any way, shape, or form. The word "dollar" is not attached to them in any way. The "$" symbol is not used in any way.

Bitcoins have no representational similarity whatsoever to US dollars.

Of course, actually 'shutting down' Liberty Dollars was as easy as arresting the head of the company and seizing the offices and the precious metals used as backing. The decentralized Bitcoin, with no leader, no servers, no office, and no tangible asset backing, does not have the same vulnerability.

== Bitcoin is not decentralized because the developers can dictate the software's behavior ==

The Bitcoin protocol was originally defined by Bitcoin's inventor, [[Satoshi Nakamoto]], and this protocol has now been widely accepted as the standard by the community of miners and users.

Though the developers of the original Bitcoin client still exert influence over the Bitcoin community, their power to arbitrarily modify the protocol is very limited. Since the release of Bitcoin v0.3, changes to the protocol have been minor and always in agreement with community consensus.

Protocol modifications, such as increasing the block award from 25 to 50 BTC, are not compatible with clients already running in the network. If the developers were to release a new client that the majority of miners perceives as corrupt, or in violation of the project’s aims, that client would simply not catch on, and the few users who do try to use it would find that their transactions get rejected by the network.

There are also other [[:Category:Clients|Bitcoin clients made by other developers]] that adhere to the Bitcoin protocol. As more developers create alternative clients, less power will lie with the developers of the original Bitcoin client.

== Bitcoin is a pyramid scheme ==

Bitcoin is nearly opposite of a pyramid scheme in a mathematical sense. Because Bitcoins are algorithmically made scarce, no exponential benefit is derived from introducing new users to use of it. There is a quantitative benefit in having additional interest or demand, but this is in no way exponential.

== Bitcoin was hacked ==

In the history of Bitcoin, there has never been an attack on the [[block chain]] that resulted in stolen money from a confirmed output. Neither has there ever been a reported theft resulting directly from a vulnerability in the [[Original Bitcoin client|original Bitcoin client]], or a vulnerability in the protocol. Bitcoin is secured by standard cryptographic functions. These functions have been peer reviewed by cryptography experts and are considered unlikely to be breakable in the foreseeable future.

It is safe to say that the currency itself has never been 'hacked'. However, several major ''websites'' using the currency have been hacked, often resulting in high profile Bitcoin heists. These heists are misreported in some media as hacks on Bitcoin itself. An analogy: Just because someone stole US dollars from a supermarket till, doesn’t mean that the US dollar as a currency has been 'hacked'.

Most bitcoin thefts are the result of inadequate [[Securing your wallet|wallet security]]. In response to the wave of thefts in 2011 and 2012, the community has developed risk-mitigating measures such as [[Wallet_encryption|wallet encryption]], support for [[BIP_0011|multiple signatures]], [[How_to_set_up_a_secure_offline_savings_wallet|offline wallets]], [[Paper_wallet|paper wallets]], and [[Hardware_wallet|hardware wallets]]. As these measures gain adoption by merchants and users, it is expected that the number of thefts will drop.

==References==
<references/>

[[de:Mythen]]
[[ru:Мифы о биткоине]]

Myths

2014-09-12T21:50:46Z

Atheros: /* Bitcoin makes self-sufficient artificial intelligence possible, which will in turn become self-aware and decide to exterminate humanity */ That is the dumbest thing I've ever heard.

Let's clear up some common Bitcoin misconceptions.

== Bitcoin is just like all other digital currencies; nothing new ==

Nearly all other digital currencies are centrally controlled. This means that:
* They can be printed at the subjective whims of the controllers
* They can be destroyed by attacking the central point of control
* Arbitrary rules can be imposed upon their users by the controllers

Being decentralized, Bitcoin solves all of these problems.

== Bitcoins don't solve any problems that fiat currency and/or gold doesn't solve ==

Unlike gold, bitcoins are:
* Easy to transfer
* Easy to secure
* Easy to verify
* Easy to granulate

Unlike fiat currencies, bitcoins are:
* Predictable and limited in [[Controlled_Currency_Supply|supply]]
* Not controlled by a central authority (such as [http://en.wikipedia.org/wiki/Federal_Reserve The United States Federal Reserve])
* Not debt-based

Unlike electronic fiat currency systems, bitcoins are:
* Potentially anonymous
* Freeze-proof
* Faster to transfer
* Cheaper to transfer

== Bitcoin is backed by processing power ==

It is not correct to say that Bitcoin is "backed by" processing power. A currency being "backed" means that it is pegged to something else via a central party at a certain exchange rate yet you cannot exchange bitcoins for the computing power that was used to create them. Bitcoin is in this sense not backed by anything. It is a currency in its own right. Just as gold is not backed by anything, the same applies to Bitcoin.

The Bitcoin currency is ''created'' via processing power, and the integrity of the block chain is ''protected'' by the existence of a network of powerful computing nodes from certain [[Weaknesses#Attacker_has_a_lot_of_computing_power|attacks]].

== Bitcoins are worthless because they aren't backed by anything ==

One could argue that gold isn't backed by anything either. Bitcoins have properties resulting from the system's design that allows them to be subjectively valued by individuals. This valuation is demonstrated when individuals freely exchange for or with bitcoins. Please refer to the [http://en.wikipedia.org/wiki/Subjective_theory_of_value Subjective Theory of Value].

See also: the "[[#Bitcoin_is_backed_by_processing_power|Bitcoin is backed by processing power]]" myth.

== The value of bitcoins are based on how much electricity and computing power it takes to mine them ==

This statement is an attempt to apply to Bitcoin the [http://en.wikipedia.org/wiki/Labor_theory_of_value labor theory of value], which is generally accepted as false. Just because something takes X resources to create does not mean that the resulting product will be worth X. It can be worth more, or less, depending on the utility thereof to its users.

In fact the causality is the reverse of that (this applies to the labor theory of value in general). The cost to mine bitcoins is based on how much they are worth. If bitcoins go up in value, more people will mine (because [[Mining|mining]] is profitable), thus [[difficulty]] will go up, thus the cost of mining will go up. The inverse happens if bitcoins go down in value. These effects balance out to cause mining to always cost an amount proportional to the value of bitcoins it produces.

== Bitcoins have no intrinsic value (unlike some other things) ==

This is simply not true. Each bitcoin gives the holder the ability to embed a large number of short in-transaction messages in a globally distributed and timestamped permanent data store, namely the bitcoin blockchain. There is no other similar datastore which is so widely distributed. There is a tradeoff between the exact number of messages and how quickly they can be embedded. But as of December 2013, it's fair to say that one bitcoin allows around 1000 such messages to be embedded, each within about 10 minutes of being sent, since a fee of 0.001 BTC is enough to get transactions confirmed quickly. This message embedding certainly has intrinsic value since it can be used to prove ownership of a document at a certain time, by including a one-way hash of that document in a transaction. Considering that electronic notarization services charge something like $10/document, this would give an intrinsic value of around $10,000 per bitcoin.

While some other tangible commodities do have intrinsic value, that value is generally much less than its trading price. Consider for example that gold, if it were not used as an inflation-proof store of value, but rather only for its industrial uses, would certainly not be worth what it is today, since the industrial requirements for gold are far smaller than the available supply thereof.

In any event, while historically intrinsic value, as well as other attributes like divisibility, fungibility, scarcity, durability, helped establish certain commodities as mediums of exchange, it is certainly not a prerequisite. While bitcoins are accused of lacking 'intrinsic value' in this sense, they make up for it in spades by possessing the other qualities necessary to make it a good medium of exchange, equal to or better than [http://en.wikipedia.org/wiki/Commodity_money commodity money].

Another way to think about this is to consider the value of bitcoin the global network, rather than each bitcoin in isolation. The value of an individual telephone is derived from the network it is connected to. If there was no phone network, a telephone would be useless. Similarly the value of an individual bitcoin derives from the global network of bitcoin-enabled merchants, exchanges, wallets, etc... Just like a phone is necessary to transmit vocal information through the network, a bitcoin is necessary to transmit economic information through the network.

Value is ultimately determined by what people are willing to trade for - by supply and demand.

== Bitcoins are illegal because they're not legal tender ==
In March 2013, the U.S. [http://en.wikipedia.org/wiki/Financial_Crimes_Enforcement_Network Financial Crimes Enforcement Network] issues a new set of guidelines on "de-centralized virtual currency", clearly targeting Bitcoin. Under the new guidelines, "a user of virtual currency is not a Money Services Businesses (MSB) under FinCEN's regulations and therefore is not subject to MSB registration, reporting, and record keeping regulations." <ref>[http://arstechnica.com/tech-policy/2013/03/us-regulator-bitcoin-exchanges-must-comply-with-money-laundering-laws/ US regulator: Bitcoin exchanges must comply with money-laundering laws | Ars Technica]</ref> [[Mining|Miners]], when mining bitcoins for their own personal use, aren't required to register as a MSB or Money Transmitter. <ref>[http://fincen.gov/news_room/rp/rulings/html/FIN-2014-R001.html Application of FinCEN’s Regulations to Virtual Currency Mining Operations | Fincen]</ref>

In general, there are a [http://en.wikipedia.org/wiki/Local_currency number of currencies] in existence that are not official government-backed currencies. A currency is, after all, nothing more than a convenient unit of account. While national laws may vary from country to country, and you should certainly check the laws of your jurisdiction, in general trading in any commodity, including digital currency like Bitcoin, [http://en.wikipedia.org/wiki/BerkShares BerkShares], game currencies like WoW gold, or Linden dollars, is not illegal.

== Bitcoin is a form of domestic terrorism because it only harms the economic stability of the USA and its currency ==

According to [http://en.wikipedia.org/wiki/Definitions_of_terrorism#United_States the definition of terrorism in the United States], you need to do violent activities to be considered a terrorist for legal purposes. Recent off-the-cuff remarks by politicians have no basis in law or fact.

Also, Bitcoin isn't domestic to the US or any other country. It's a worldwide community, as can be seen in this [https://bitcointalk.org/?topic=2346.0 map of Bitcoin nodes].

== Bitcoin will only enable tax evaders which will lead to the eventual downfall of civilization ==

Cash transactions hold the same level of anonymity but are still taxed successfully. It is up to you to follow the applicable state laws in your home country, or face the consequences.

While it may be easy to transfer bitcoins anonymously, ''spending'' them anonymously on tangibles is just as hard as spending any other kind of money anonymously. Tax evaders are often caught because their lifestyle and assets are inconsistent with their reported income, and not necessarily because government is able to follow their money.

== Bitcoins can be printed/minted by anyone and are therefore worthless ==

Bitcoins are not printed/minted. Instead, [[Blocks]] are computed by miners and for their efforts they are awarded a specific amount of bitcoins and transaction fees paid by others. See [[Mining]] for more information on how this process works.

== Bitcoins are worthless because they're based on unproven cryptography ==

SHA256 and ECDSA which are used in Bitcoin are well-known industry standard algorithms. SHA256 is endorsed and used by the US Government and is standardized (FIPS180-3 Secure Hash Standard). If you believe that these algorithms are untrustworthy then you should not trust Bitcoin, credit card transactions or any type of electronic bank transfer. Bitcoin has a sound basis in well understood cryptography.

== Early adopters are unfairly rewarded ==

Early adopters are rewarded for taking the higher risk with their time and money. The capital invested in bitcoin at each stage of its life invigorated the community and helped the currency to reach subsequent milestones. Arguing that early adopters do not deserve to profit from this is akin to saying that early investors in a company, or people who buy stock at a company IPO (Initial Public Offering), are unfairly rewarded.

This argument also depends on bitcoin early adopters using bitcoins to store rather than transfer value. The daily trade on the exchanges (as of Jan 2012) indicates that smaller transactions are becoming the norm, indicating trade rather than investment. In more pragmatic terms, "fairness" is an arbitrary concept that is improbable to be agreed upon by a large population. Establishing "fairness" is no goal of Bitcoin, as this would be impossible.

Looking forwards, considering the amount of publicity bitcoin received as of April 2013, there can be no reasonable grounds for complaint for people who did not invest at that time, and then see the value (possibly) rising drastically higher.

By starting to mine or acquire bitcoins today, you too can become an early adopter.

== 21 million coins isn't enough; doesn't scale ==

One Bitcoin is divisible down to eight decimal places. There are really 2,099,999,997,690,000 (just over 2 quadrillion) maximum possible atomic units in the bitcoin system.

The value of "1 BTC" represents 100,000,000 of these. In other words, each is divisible by up to 10^8.

As the value of the unit of 1 BTC grows too large to be useful for day to day transactions, people can start dealing in smaller [[Units|units]], such as milli-bitcoins (mBTC) or micro-bitcoins (μBTC).

== Bitcoins are stored in wallet files, just copy the wallet file to get more coins! ==

No, your wallet contains your secret keys, giving you the rights to spend your bitcoins. Think of it like having bank details stored in a file. If you give your bank details (or bitcoin wallet) to someone else, that doesn't double the amount of money in your account. You can spend your money or they can spend your money, but not both.

== Lost coins can't be replaced and this is bad ==

Bitcoins are divisible to 0.00000001, so there being fewer bitcoins remaining is not a problem for the currency itself. If you lose your coins, all other coins will go up in value a little. Consider it a donation to all other bitcoin users.

A related question is: Why don't we have a mechanism to replace lost coins? The answer is that it is impossible to distinguish between a 'lost' coin and one that is simply sitting unused in someone's wallet.

== It's a giant ponzi scheme ==
In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. In a ponzi scheme, early adopters can only profit at the expense of late adopters, and the late adopters always lose. Bitcoin has an expected win-win outcome. Early and present adopters profit from the rise in value as Bitcoins become better understood and in turn demanded by the public at large. All adopters benefit from the usefulness of a reliable and widely-accepted decentralized peer-to-peer currency.

== Finite coins plus lost coins means deflationary spiral ==
As deflationary forces may apply, economic factors such as hoarding are offset by human factors that may lessen the chances that a [[Deflationary spiral]] will occur.

== Bitcoin can't work because there is no way to control inflation ==

Inflation is simply a rise of prices over time, which is generally the result of the devaluing of a currency. This is a function of supply and demand. Given the fact that the supply of bitcoins is fixed at a certain amount, unlike fiat money, the only way for inflation to get out of control is for demand to disappear. Temporary inflation is possible with a rapid adoption of Fractional Reserve Banking but will stabilize once a substantial number of the 21 million "hard" bitcoins are stored as reserves by banks.

Given the fact that Bitcoin is a distributed system of currency, if demand were to decrease to almost nothing, the currency would be doomed anyway.

The key point here is that Bitcoin as a currency can't be inflated by any single person or entity, like a government, as there's no way to increase supply past a certain amount.

Indeed, the most likely scenario, as Bitcoin becomes more popular and demand increases, is for the currency to increase in value, or deflate, until demand stabilizes.

== The Bitcoin community consists of anarchist/conspiracy theorist/gold standard 'weenies' ==

The members of the community vary in their ideological stances. While it may have been started by ideological enthusiasts, Bitcoin now speaks to a large number of regular pragmatic folk, who simply see its potential for reducing the costs and friction of global e-commerce.

== Anyone with enough computing power can take over the network ==

CONFIRMED, see [[Weaknesses]].

That said, as the network grows, it becomes harder and harder for a single entity to do so. Already the Bitcoin network's computing power is quite ahead of the world's fastest supercomputers, together.

What an attacker can do once the network is taken over is quite limited. Under no circumstances could an attacker create counterfeit coins, fake transactions, or take anybody else's money. An attacker's capabilities are limited to taking back their own money that they very recently spent, and preventing other people's transactions from receiving confirmations. Such an attack would be very costly in resources, and for such meager benefits there is little rational economic incentive to do such a thing.

Furthermore, this attack scenario would only be feasible for as long as it was actively underway. As soon as the attack stopped, the network would resume normal operation.

== Bitcoin violates governmental regulations ==

There is no known governmental regulation which disallows the use of Bitcoin.

See also: the "[[#Bitcoins_are_illegal_because_they.27re_not_legal_tender|Bitcoins are illegal because they're not legal tender]]" myth.

== Fractional reserve banking is not possible ==

It is possible. See the main article, [[Fractional Reserve Banking and Bitcoin]]

== After 21 million coins are mined, no one will generate new blocks ==

When operating costs can't be covered by the block creation bounty, which will happen some time before the total amount of BTC is reached, miners will earn some profit from [[transaction fees]]. However unlike the block reward, there is [http://bitcoin.stackexchange.com/questions/876/how-much-will-transaction-fees-eventually-be/895#895 no coupling between transaction fees and the need for security], so there is less of a guarantee that the amount of [[Mining|mining]] being performed will be sufficient to maintain the network's security.

== Bitcoin has no built-in chargeback mechanism, and this isn't good ==

'''Why some people think this is bad''': Chargebacks are useful for limiting fraud. The person handling your money has a responsibility to prevent fraud. If you buy something on eBay and the seller never ships it, PayPal takes funds from the seller's account and gives you back the money. This strengthens the eBay economy, because people recognize that their risk is limited and are more willing to purchase items from risky sellers.

'''Why it's actually a good thing''': Bitcoin is designed such that your money is yours and yours alone. Allowing chargebacks implies that it is possible for another entity to take your money from you. You can have either total ownership rights of your money, or fraud protection, but not both. That said, nothing inherent in the dollar or euro or any other currency is necessary for chargebacks to be possible, and likewise, nothing prevents the creation of PayPal-like services denominated in Bitcoin that provide chargebacks or fraud protection.

The statement "The person handling your money has a responsibility to prevent fraud" is still true; the power has been shifted into your own hands. Fraud will always exist. It's up to you to only send bitcoins to trusted entities. It is possible to trust an online identity without ever knowing their physical identity; see the [http://wiki.bitcoin-otc.com/wiki/OTC_Rating_System OTC Web of Trust].

== Quantum computers would break Bitcoin's security ==

While ECDSA is indeed not secure under quantum computing, quantum computers don't yet exist and probably won't for a while.
The DWAVE system often written about in the press is, even if all their claims are true, not a quantum computer of a kind that could be used for cryptography.
Bitcoin's security, when used properly with a new address on each transaction, depends on more than just ECDSA: Cryptographic hashes are much stronger than ECDSA under QC.
Bitcoin's security was designed to be upgraded in a forward compatible way and could be [http://en.wikipedia.org/wiki/Post-quantum_cryptography upgraded] if this were considered an imminent threat.

See the implications of quantum computers on public key cryptography here http://en.wikipedia.org/wiki/Quantum_computer#Potential

The ''risk'' of quantum computers is also there for financial institutions, like banks, because they heavily rely on cryptography when doing transactions.

== [[Mining|Bitcoin mining]] is a waste of energy and harmful for ecology ==
No more so than the wastefulness of mining gold out of the ground, melting it down and shaping it into bars, and then putting it back underground again. Not to mention the building of big fancy buildings, the waste of energy printing and minting all the various fiat currencies, the transportation thereof in armored cars by no less than two security guards for each who could probably be doing something more productive, etc.

As far as mediums of exchange go, Bitcoin is actually quite economical of resources, compared to others.

'''Economic Argument 1'''

[[Mining|Bitcoin mining]] is a highly competitive, dynamic, almost [http://en.wikipedia.org/wiki/Perfect_market perfect], market. Mining rigs can be set up and dismantled almost anywhere in the world with relative ease. Thus, market forces are constantly pushing mining activity to ''places'' and ''times'' where the marginal price of electricity is low or zero. These electricity products are cheap for a reason. Often it’s because the electricity is difficult (and wasteful) to transport, difficult to store, or because there is low demand and high supply. Using electricity in this way is a lot less wasteful than simply plugging a mining rig into the mains indiscriminately.

For example, Iceland produces an excess of cheap electricity from renewable sources, but it has no way of exporting electricity because of its remote location. It is conceivable that at some point in future Bitcoin mining will only be profitable in places like Iceland, and unprofitable in places like central Europe, where electricity comes mostly from nuclear and fossil sources.

Market forces could even push mining into innovative solutions that have an effective electricity consumption of ''zero''. Mining always produces heat equivalent to the energy consumed - for example, 1000 watts of mining equipment produces the same amount of heat as a 1000 watt heating element used in an electric space heater, hot tub, water heater, or similar appliance. Someone already in a willing position to incur the cost of electricity for its heat value alone could run mining equipment specially designed to mine bitcoins while capturing and utilizing the heat produced, without incurring any energy costs beyond what they already intended to spend on heating.

(Note that this is just an example; mining will not always produce heat equivalent to the energy consumed because some energy is inevitably released as electromagnetic radiation, among others.)

'''Economic Argument 2'''

When the environmental costs of mining are considered, they need to be weighed up against the benefits. If you question Bitcoin on the grounds that it consumes electricity, then you should also ask questions like this: Will Bitcoin promote economic growth by freeing up trade? Will this speed up the rate of technological innovation? Will this lead to faster development of green technologies? Will Bitcoin enable new, border crossing [http://en.wikipedia.org/wiki/Smart_grid smart grid] technologies? …

Dismissal of Bitcoin because of its costs, while ignoring its benefits, is a dishonest argument. In fact, any environmental argument of this type is dishonest, not just pertaining to Bitcoin. Along similar lines, it could be argued that wind turbines are bad for the environment because making the steel structure consumes energy.

'''Ratio of Capital Costs versus Electrical Costs'''

The BFL Jalapeno hashes at 5.5 Gh/s using 30W. That device consumes about $40 per year in electricity (using U.S. residential average of about $0.15 per kWh.) But the device costs over $300 including shipping. Thus just about a quarter of all costs over a two-year useful life goes to electricity. This compares to GPUs where more than 90% of costs over a two-year life went to electricity. Even more efficient designs can be expected in the future.

== Shopkeepers can't seriously set prices in bitcoins because of the volatile exchange rate ==

The assumption is that bitcoins must be sold immediately to cover operating expenses. If the shopkeeper's back-end expenses were transacted in bitcoins as well, then the exchange rate would be irrelevant. Larger adoption of Bitcoin would make prices [http://en.wikipedia.org/wiki/Sticky_%28economics%29 sticky]. Future volatility is expected to decrease, as the size and depth of the market grows.

In the meantime, many merchants simply regularly pull the latest market rates from the exchanges and automatically update the prices on their websites. Also you might be able to buy a put option in order to sell at a fixed rate for a given amount of time. This would protect you from drops in price and simplify your operations for that time period.

== Like Flooz and e-gold, bitcoins serve as opportunities for criminals and will be shut down ==

* Visa, MasterCard, PayPal, and cash all serve as opportunities for criminals as well, but society keeps them around due to their recognized net benefit.
* Hopefully Bitcoin will grow to the point where no single organization can disrupt the network, or would be better served by helping it.
* Terrorists fly aircraft into buildings, but the governments have not yet abolished consumer air travel. Obviously the public good outweighs the possible bad in their opinion.
* Criminal law differs between jurisdictions.

== Bitcoins will be shut down by the government just like Liberty Dollars were ==

Liberty Dollars started as a commercial venture to establish an alternative US currency, including physical banknotes and coins, backed by precious metals. This, in and of itself, is not illegal. They were prosecuted under counterfeiting laws because the silver coins allegedly resembled US currency.

Bitcoins do not resemble the currency of the US or of any other nation in any way, shape, or form. The word "dollar" is not attached to them in any way. The "$" symbol is not used in any way.

Bitcoins have no representational similarity whatsoever to US dollars.

Of course, actually 'shutting down' Liberty Dollars was as easy as arresting the head of the company and seizing the offices and the precious metals used as backing. The decentralized Bitcoin, with no leader, no servers, no office, and no tangible asset backing, does not have the same vulnerability.

== Bitcoin is not decentralized because the developers can dictate the software's behavior ==

The Bitcoin protocol was originally defined by Bitcoin's inventor, [[Satoshi Nakamoto]], and this protocol has now been widely accepted as the standard by the community of miners and users.

Though the developers of the original Bitcoin client still exert influence over the Bitcoin community, their power to arbitrarily modify the protocol is very limited. Since the release of Bitcoin v0.3, changes to the protocol have been minor and always in agreement with community consensus.

Protocol modifications, such as increasing the block award from 25 to 50 BTC, are not compatible with clients already running in the network. If the developers were to release a new client that the majority of miners perceives as corrupt, or in violation of the project’s aims, that client would simply not catch on, and the few users who do try to use it would find that their transactions get rejected by the network.

There are also other [[:Category:Clients|Bitcoin clients made by other developers]] that adhere to the Bitcoin protocol. As more developers create alternative clients, less power will lie with the developers of the original Bitcoin client.

== Bitcoin is a pyramid scheme ==

Bitcoin is nearly opposite of a pyramid scheme in a mathematical sense. Because Bitcoins are algorithmically made scarce, no exponential benefit is derived from introducing new users to use of it. There is a quantitative benefit in having additional interest or demand, but this is in no way exponential.

== Bitcoin was hacked ==

In the history of Bitcoin, there has never been an attack on the [[block chain]] that resulted in stolen money from a confirmed output. Neither has there ever been a reported theft resulting directly from a vulnerability in the [[Original Bitcoin client|original Bitcoin client]], or a vulnerability in the protocol. Bitcoin is secured by standard cryptographic functions. These functions have been peer reviewed by cryptography experts and are considered unlikely to be breakable in the foreseeable future.

It is safe to say that the currency itself has never been 'hacked'. However, several major ''websites'' using the currency have been hacked, often resulting in high profile Bitcoin heists. These heists are misreported in some media as hacks on Bitcoin itself. An analogy: Just because someone stole US dollars from a supermarket till, doesn’t mean that the US dollar as a currency has been 'hacked'.

Most bitcoin thefts are the result of inadequate [[Securing your wallet|wallet security]]. In response to the wave of thefts in 2011 and 2012, the community has developed risk-mitigating measures such as [[Wallet_encryption|wallet encryption]], support for [[BIP_0011|multiple signatures]], [[How_to_set_up_a_secure_offline_savings_wallet|offline wallets]], [[Paper_wallet|paper wallets]], and [[Hardware_wallet|hardware wallets]]. As these measures gain adoption by merchants and users, it is expected that the number of thefts will drop.

==References==
<references/>

[[de:Mythen]]
[[ru:Мифы о биткоине]]

Controlled supply

2014-07-08T21:18:46Z

Atheros: Removed 21M justification because it is too poorly written. Please come up with a vastly more clear way to write it before readding it.

In a centralized economy, currency is issued by a central bank at a rate that is supposed to match the growth of the amount of goods that are exchanged so that these goods can be traded with stable prices. The
[http://en.wikipedia.org/wiki/Monetary_base monetary base] is controlled by a central bank. In the United States, the [http://en.wikipedia.org/wiki/Federal_Reserve_System Fed] increases the monetary base by issuing currency, increasing the amount banks have on reserve, and more recently, printing money electronically in a process called [http://en.wikipedia.org/wiki/Quantitative_easing Quantitative Easing].

In a fully decentralized monetary system, there is no central authority that regulates the monetary base. Instead, currency is created by the nodes of a peer-to-peer network. The Bitcoin generation algorithm defines, in advance, how currency will be created and at what rate. Any currency that is generated by a malicious user that does not follow the rules will be rejected by the network and thus is worthless.

==Currency with Finite Supply==

[[File:total_bitcoins_over_time_graph.png|thumb|Number of bitcoins over time]]

Bitcoins are created each time a user discovers a new [[block]].
The rate of block creation is approximately constant over time: 6 per hour. The
number of Bitcoins generated per block is set to decrease geometrically, with a 50% reduction every 4 years. The result is that the number of Bitcoins in existence will
never exceed 21 million<ref>[http://www.bitcointalk.org/index.php?topic=3366.msg47522#msg47522 21 million cap]</ref>. This algorithm was chosen because it approximates the rate at which commodities like gold are mined. Users who use their computers to perform calculations to try and discover a block are thus called [[Mining|''Miners'']].

==Projected Bitcoins Short Term ==
This chart shows the number of bitcoins that will exist in the near future. The ''Year'' is a forecast and may be slightly off.
{| class="wikitable"
|-
! Block!!Reward Era!! BTC/block!! Year!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
|0||1||50.00||2009||0||2625000||2625000||infinite||12.500%
|-
|52500||1||50.00||2010||2625000||2625000||5250000||100.00%||25.000%
|-
|105000||1||50.00||2011||5250000||2625000||7875000||50.00%||37.500%
|-
|157500||1||50.00||2012||7875000||2625000||10500000||33.33%||50.000%
|-
|210000||2||25.00||2013||10500000||1312500||11812500||12.50%||56.250%
|-
|262500||2||25.00||2014||11812500||1312500||13125000||11.11%||62.500%
|-
|315000||2||25.00||2015||13125000||1312500||14437500||10.00%||68.750%
|-
|367500||2||25.00||2016||14437500||1312500||15750000||9.09%||75.000%
|-
|420000||3||12.50||2017||15750000||656250||16406250||4.17%||78.125%
|-
|472500||3||12.50||2018||16406250||656250||17062500||4.00%||81.250%
|-
|525000||3||12.50||2019||17062500||656250||17718750||3.85%||84.375%
|-
|577500||3||12.50||2020||17718750||656250||18375000||3.70%||87.500%
|-
|630000||4||6.25||2021||18375000||328125||18703125||1.79%||89.063%
|-
|682500||4||6.25||2022||18703125||328125||19031250||1.75%||90.625%
|-
|735000||4||6.25||2023||19031250||328125||19359375||1.72%||92.188%
|-
|787500||4||6.25||2024||19359375||328125||19687500||1.69%||93.750%
|}

==Projected Bitcoins Long Term ==

{| class="wikitable"
|-
! Block!!Reward Era!! BTC/block!! Year!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
| 0|| 1|| 50.00000000||2009.007|| 0.00000000|| 10500000.00000000|| 10500000.00000000|| infinite|| 50.00000006%
|-
| 210000|| 2|| 25.00000000||2013.000|| 10500000.00000000|| 5250000.00000000|| 15750000.00000000|| 50.00000000%|| 75.00000008%
|-
| 420000|| 3|| 12.50000000||2016.993|| 15750000.00000000|| 2625000.00000000|| 18375000.00000000|| 16.66666667%|| 87.50000010%
|-
| 630000|| 4|| 6.25000000||2020.986|| 18375000.00000000|| 1312500.00000000|| 19687500.00000000|| 7.14285714%|| 93.75000010%
|-
| 840000|| 5|| 3.12500000||2024.978|| 19687500.00000000|| 656250.00000000|| 20343750.00000000|| 3.33333333%|| 96.87500011%
|-
| 1050000|| 6|| 1.56250000||2028.971|| 20343750.00000000|| 328125.00000000|| 20671875.00000000|| 1.61290323%|| 98.43750011%
|-
| 1260000|| 7|| 0.78125000||2032.964|| 20671875.00000000|| 164062.50000000|| 20835937.50000000|| 0.79365079%|| 99.21875011%
|-
| 1470000|| 8|| 0.39062500||2036.956|| 20835937.50000000|| 82031.25000000|| 20917968.75000000|| 0.39370079%|| 99.60937511%
|-
| 1680000|| 9|| 0.19531250||2040.949|| 20917968.75000000|| 41015.62500000|| 20958984.37500000|| 0.19607843%|| 99.80468761%
|-
| 1890000|| 10|| 0.09765625||2044.942|| 20958984.37500000|| 20507.81250000|| 20979492.18750000|| 0.09784736%|| 99.90234386%
|-
| 2100000|| 11|| 0.04882812||2048.934|| 20979492.18750000|| 10253.90520000|| 20989746.09270000|| 0.04887585%|| 99.95117198%
|-
| 2310000|| 12|| 0.02441406||2052.927|| 20989746.09270000|| 5126.95260000|| 20994873.04530000|| 0.02442599%|| 99.97558604%
|-
| 2520000|| 13|| 0.01220703||2056.920|| 20994873.04530000|| 2563.47630000|| 20997436.52160000|| 0.01221001%|| 99.98779307%
|-
| 2730000|| 14|| 0.00610351||2060.913|| 20997436.52160000|| 1281.73710000|| 20998718.25870000|| 0.00610426%|| 99.99389658%
|-
| 2940000|| 15|| 0.00305175||2064.905|| 20998718.25870000|| 640.86750000|| 20999359.12620000|| 0.00305194%|| 99.99694833%
|-
| 3150000|| 16|| 0.00152587||2068.898|| 20999359.12620000|| 320.43270000|| 20999679.55890000|| 0.00152592%|| 99.99847420%
|-
| 3360000|| 17|| 0.00076293||2072.891|| 20999679.55890000|| 160.21530000|| 20999839.77420000|| 0.00076294%|| 99.99923713%
|-
| 3570000|| 18|| 0.00038146||2076.883|| 20999839.77420000|| 80.10660000|| 20999919.88080001|| 0.00038146%|| 99.99961859%
|-
| 3780000|| 19|| 0.00019073||2080.876|| 20999919.88080001|| 40.05330000|| 20999959.93410001|| 0.00019073%|| 99.99980932%
|-
| 3990000|| 20|| 0.00009536||2084.869|| 20999959.93410001|| 20.02560000|| 20999979.95970001|| 0.00009536%|| 99.99990468%
|-
| 4200000|| 21|| 0.00004768||2088.861|| 20999979.95970001|| 10.01280000|| 20999989.97250001|| 0.00004768%|| 99.99995236%
|-
| 4410000|| 22|| 0.00002384||2092.854|| 20999989.97250001|| 5.00640000|| 20999994.97890001|| 0.00002384%|| 99.99997620%
|-
| 4620000|| 23|| 0.00001192||2096.847|| 20999994.97890001|| 2.50320000|| 20999997.48210001|| 0.00001192%|| 99.99998812%
|-
| 4830000|| 24|| 0.00000596||2100.840|| 20999997.48210001|| 1.25160000|| 20999998.73370001|| 0.00000596%|| 99.99999408%
|-
| 5040000|| 25|| 0.00000298||2104.832|| 20999998.73370001|| 0.62580000|| 20999999.35950001|| 0.00000298%|| 99.99999706%
|-
| 5250000|| 26|| 0.00000149||2108.825|| 20999999.35950001|| 0.31290000|| 20999999.67240001|| 0.00000149%|| 99.99999855%
|-
| 5460000|| 27|| 0.00000074||2112.818|| 20999999.67240001|| 0.15540000|| 20999999.82780001|| 0.00000074%|| 99.99999929%
|-
| 5670000|| 28|| 0.00000037||2116.810|| 20999999.82780001|| 0.07770000|| 20999999.90550001|| 0.00000037%|| 99.99999966%
|-
| 5880000|| 29|| 0.00000018||2120.803|| 20999999.90550001|| 0.03780000|| 20999999.94330001|| 0.00000018%|| 99.99999984%
|-
| 6090000|| 30|| 0.00000009||2124.796|| 20999999.94330001|| 0.01890000|| 20999999.96220000|| 0.00000009%|| 99.99999993%
|-
| 6300000|| 31|| 0.00000004||2128.788|| 20999999.96220000|| 0.00840000|| 20999999.97060001|| 0.00000004%|| 99.99999997%
|-
| 6510000|| 32|| 0.00000002||2132.781|| 20999999.97060001|| 0.00420000|| 20999999.97480001|| 0.00000002%|| 99.99999999%
|-
| 6720000|| 33|| 0.00000001||2136.774|| 20999999.97480001|| 0.00210000|| 20999999.97690000|| 0.00000001%|| 100.00000000%
|-
| 6930000|| 34|| 0.00000000||2140.767|| 20999999.97690000|| 0.00000000|| 20999999.97690000|| 0.00000000%|| 100.00000000%
|}
==Money Supply==

While the number of bitcoins in existence will never exceed 21 million, the [http://en.wikipedia.org/wiki/Money_supply money supply] of bitcoins can exceed 21 million due to [http://en.wikipedia.org/wiki/Fractional-reserve_banking Fractional-reserve Banking]. 

==Deflation==

Because the monetary base of bitcoins cannot be expanded, the currency would be subject to severe deflation if it becomes widely used.
Keynesian economists argue that [[Deflationary spiral|deflation]] is bad for an economy because it incentivises individuals and businesses to save money rather than invest in businesses and create jobs. The [http://en.wikipedia.org/wiki/Austrian_School Austrian school] of thought counters this criticism, claiming that as deflation occurs in all stages of production, entrepreneurs who invest benefit from it. As a result, profit ratios tend to stay the same and only their magnitudes change. In other words, in a deflationary environment, goods and services decrease in price, but at the same time the cost for the production of these goods and services tend to decrease proportionally, effectively not affecting profits. Price deflation encourages an increase in hoarding — hence savings — which in turn tends to lower interest rates and increase the incentive for entrepreneurs to invest in projects of longer term.

==See also==

* [http://www.econlib.org/library/Columns/y2006/Friedmantranscript.html Milton Friedman interview], where he proposed to replace the central bank with a computer, and to fix the money supply growth at 4% annually
* [[Deflationary spiral]]
* [http://blockchain.info/charts/total-bitcoins Chart of total bitcoins in circulation]
==References==
<references />

[[Category:Economics]]

Controlled supply

2014-07-08T21:13:31Z

Atheros: Put the graph back in. How is this misleading? Please comment on the discussion page.

In a centralized economy, currency is issued by a central bank at a rate that is supposed to match the growth of the amount of goods that are exchanged so that these goods can be traded with stable prices. The
[http://en.wikipedia.org/wiki/Monetary_base monetary base] is controlled by a central bank. In the United States, the [http://en.wikipedia.org/wiki/Federal_Reserve_System Fed] increases the monetary base by issuing currency, increasing the amount banks have on reserve, and more recently, printing money electronically in a process called [http://en.wikipedia.org/wiki/Quantitative_easing Quantitative Easing].

In a fully decentralized monetary system, there is no central authority that regulates the monetary base. Instead, currency is created by the nodes of a peer-to-peer network. The Bitcoin generation algorithm defines, in advance, how currency will be created and at what rate. Any currency that is generated by a malicious user that does not follow the rules will be rejected by the network and thus is worthless.

==Currency with Finite Supply==

[[File:total_bitcoins_over_time_graph.png|thumb|Number of bitcoins over time]]

Bitcoins are created each time a user discovers a new [[block]].
The rate of block creation is approximately constant over time: 6 per hour. The
number of Bitcoins generated per block is set to decrease geometrically, with a 50% reduction every 4 years. The result is that the number of Bitcoins in existence will
never exceed 21 million<ref>[http://www.bitcointalk.org/index.php?topic=3366.msg47522#msg47522 21 million cap]</ref>. This algorithm was chosen because it approximates the rate at which commodities like gold are mined. Possible justifications for the value 21 million are that it matches a 4-year reward halving schedule or that 2.1*10^15 (the maximum number of Satoshis) is close to the maximum exact capacity of a 64-bit floating point number. Users who use their computers to perform calculations to try and discover a block are thus called [[Mining|''Miners'']].

==Projected Bitcoins Short Term ==
This chart shows the number of bitcoins that will exist in the near future. The ''Year'' is a forecast and may be slightly off.
{| class="wikitable"
|-
! Block!!Reward Era!! BTC/block!! Year!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
|0||1||50.00||2009||0||2625000||2625000||infinite||12.500%
|-
|52500||1||50.00||2010||2625000||2625000||5250000||100.00%||25.000%
|-
|105000||1||50.00||2011||5250000||2625000||7875000||50.00%||37.500%
|-
|157500||1||50.00||2012||7875000||2625000||10500000||33.33%||50.000%
|-
|210000||2||25.00||2013||10500000||1312500||11812500||12.50%||56.250%
|-
|262500||2||25.00||2014||11812500||1312500||13125000||11.11%||62.500%
|-
|315000||2||25.00||2015||13125000||1312500||14437500||10.00%||68.750%
|-
|367500||2||25.00||2016||14437500||1312500||15750000||9.09%||75.000%
|-
|420000||3||12.50||2017||15750000||656250||16406250||4.17%||78.125%
|-
|472500||3||12.50||2018||16406250||656250||17062500||4.00%||81.250%
|-
|525000||3||12.50||2019||17062500||656250||17718750||3.85%||84.375%
|-
|577500||3||12.50||2020||17718750||656250||18375000||3.70%||87.500%
|-
|630000||4||6.25||2021||18375000||328125||18703125||1.79%||89.063%
|-
|682500||4||6.25||2022||18703125||328125||19031250||1.75%||90.625%
|-
|735000||4||6.25||2023||19031250||328125||19359375||1.72%||92.188%
|-
|787500||4||6.25||2024||19359375||328125||19687500||1.69%||93.750%
|}

==Projected Bitcoins Long Term ==

{| class="wikitable"
|-
! Block!!Reward Era!! BTC/block!! Year!! Start BTC!! BTC Added!! End BTC!! BTC Increase|| End BTC % of Limit
|-
| 0|| 1|| 50.00000000||2009.007|| 0.00000000|| 10500000.00000000|| 10500000.00000000|| infinite|| 50.00000006%
|-
| 210000|| 2|| 25.00000000||2013.000|| 10500000.00000000|| 5250000.00000000|| 15750000.00000000|| 50.00000000%|| 75.00000008%
|-
| 420000|| 3|| 12.50000000||2016.993|| 15750000.00000000|| 2625000.00000000|| 18375000.00000000|| 16.66666667%|| 87.50000010%
|-
| 630000|| 4|| 6.25000000||2020.986|| 18375000.00000000|| 1312500.00000000|| 19687500.00000000|| 7.14285714%|| 93.75000010%
|-
| 840000|| 5|| 3.12500000||2024.978|| 19687500.00000000|| 656250.00000000|| 20343750.00000000|| 3.33333333%|| 96.87500011%
|-
| 1050000|| 6|| 1.56250000||2028.971|| 20343750.00000000|| 328125.00000000|| 20671875.00000000|| 1.61290323%|| 98.43750011%
|-
| 1260000|| 7|| 0.78125000||2032.964|| 20671875.00000000|| 164062.50000000|| 20835937.50000000|| 0.79365079%|| 99.21875011%
|-
| 1470000|| 8|| 0.39062500||2036.956|| 20835937.50000000|| 82031.25000000|| 20917968.75000000|| 0.39370079%|| 99.60937511%
|-
| 1680000|| 9|| 0.19531250||2040.949|| 20917968.75000000|| 41015.62500000|| 20958984.37500000|| 0.19607843%|| 99.80468761%
|-
| 1890000|| 10|| 0.09765625||2044.942|| 20958984.37500000|| 20507.81250000|| 20979492.18750000|| 0.09784736%|| 99.90234386%
|-
| 2100000|| 11|| 0.04882812||2048.934|| 20979492.18750000|| 10253.90520000|| 20989746.09270000|| 0.04887585%|| 99.95117198%
|-
| 2310000|| 12|| 0.02441406||2052.927|| 20989746.09270000|| 5126.95260000|| 20994873.04530000|| 0.02442599%|| 99.97558604%
|-
| 2520000|| 13|| 0.01220703||2056.920|| 20994873.04530000|| 2563.47630000|| 20997436.52160000|| 0.01221001%|| 99.98779307%
|-
| 2730000|| 14|| 0.00610351||2060.913|| 20997436.52160000|| 1281.73710000|| 20998718.25870000|| 0.00610426%|| 99.99389658%
|-
| 2940000|| 15|| 0.00305175||2064.905|| 20998718.25870000|| 640.86750000|| 20999359.12620000|| 0.00305194%|| 99.99694833%
|-
| 3150000|| 16|| 0.00152587||2068.898|| 20999359.12620000|| 320.43270000|| 20999679.55890000|| 0.00152592%|| 99.99847420%
|-
| 3360000|| 17|| 0.00076293||2072.891|| 20999679.55890000|| 160.21530000|| 20999839.77420000|| 0.00076294%|| 99.99923713%
|-
| 3570000|| 18|| 0.00038146||2076.883|| 20999839.77420000|| 80.10660000|| 20999919.88080001|| 0.00038146%|| 99.99961859%
|-
| 3780000|| 19|| 0.00019073||2080.876|| 20999919.88080001|| 40.05330000|| 20999959.93410001|| 0.00019073%|| 99.99980932%
|-
| 3990000|| 20|| 0.00009536||2084.869|| 20999959.93410001|| 20.02560000|| 20999979.95970001|| 0.00009536%|| 99.99990468%
|-
| 4200000|| 21|| 0.00004768||2088.861|| 20999979.95970001|| 10.01280000|| 20999989.97250001|| 0.00004768%|| 99.99995236%
|-
| 4410000|| 22|| 0.00002384||2092.854|| 20999989.97250001|| 5.00640000|| 20999994.97890001|| 0.00002384%|| 99.99997620%
|-
| 4620000|| 23|| 0.00001192||2096.847|| 20999994.97890001|| 2.50320000|| 20999997.48210001|| 0.00001192%|| 99.99998812%
|-
| 4830000|| 24|| 0.00000596||2100.840|| 20999997.48210001|| 1.25160000|| 20999998.73370001|| 0.00000596%|| 99.99999408%
|-
| 5040000|| 25|| 0.00000298||2104.832|| 20999998.73370001|| 0.62580000|| 20999999.35950001|| 0.00000298%|| 99.99999706%
|-
| 5250000|| 26|| 0.00000149||2108.825|| 20999999.35950001|| 0.31290000|| 20999999.67240001|| 0.00000149%|| 99.99999855%
|-
| 5460000|| 27|| 0.00000074||2112.818|| 20999999.67240001|| 0.15540000|| 20999999.82780001|| 0.00000074%|| 99.99999929%
|-
| 5670000|| 28|| 0.00000037||2116.810|| 20999999.82780001|| 0.07770000|| 20999999.90550001|| 0.00000037%|| 99.99999966%
|-
| 5880000|| 29|| 0.00000018||2120.803|| 20999999.90550001|| 0.03780000|| 20999999.94330001|| 0.00000018%|| 99.99999984%
|-
| 6090000|| 30|| 0.00000009||2124.796|| 20999999.94330001|| 0.01890000|| 20999999.96220000|| 0.00000009%|| 99.99999993%
|-
| 6300000|| 31|| 0.00000004||2128.788|| 20999999.96220000|| 0.00840000|| 20999999.97060001|| 0.00000004%|| 99.99999997%
|-
| 6510000|| 32|| 0.00000002||2132.781|| 20999999.97060001|| 0.00420000|| 20999999.97480001|| 0.00000002%|| 99.99999999%
|-
| 6720000|| 33|| 0.00000001||2136.774|| 20999999.97480001|| 0.00210000|| 20999999.97690000|| 0.00000001%|| 100.00000000%
|-
| 6930000|| 34|| 0.00000000||2140.767|| 20999999.97690000|| 0.00000000|| 20999999.97690000|| 0.00000000%|| 100.00000000%
|}
==Money Supply==

While the number of bitcoins in existence will never exceed 21 million, the [http://en.wikipedia.org/wiki/Money_supply money supply] of bitcoins can exceed 21 million due to [http://en.wikipedia.org/wiki/Fractional-reserve_banking Fractional-reserve Banking]. 

==Deflation==

Because the monetary base of bitcoins cannot be expanded, the currency would be subject to severe deflation if it becomes widely used.
Keynesian economists argue that [[Deflationary spiral|deflation]] is bad for an economy because it incentivises individuals and businesses to save money rather than invest in businesses and create jobs. The [http://en.wikipedia.org/wiki/Austrian_School Austrian school] of thought counters this criticism, claiming that as deflation occurs in all stages of production, entrepreneurs who invest benefit from it. As a result, profit ratios tend to stay the same and only their magnitudes change. In other words, in a deflationary environment, goods and services decrease in price, but at the same time the cost for the production of these goods and services tend to decrease proportionally, effectively not affecting profits. Price deflation encourages an increase in hoarding — hence savings — which in turn tends to lower interest rates and increase the incentive for entrepreneurs to invest in projects of longer term.

==See also==

* [http://www.econlib.org/library/Columns/y2006/Friedmantranscript.html Milton Friedman interview], where he proposed to replace the central bank with a computer, and to fix the money supply growth at 4% annually
* [[Deflationary spiral]]
* [http://blockchain.info/charts/total-bitcoins Chart of total bitcoins in circulation]
==References==
<references />

[[Category:Economics]]

Mining

2014-07-08T20:56:18Z

Atheros: /* ASIC Mining */ grammar

[[File:Quick-and-dirty-4x5970-cooling.jpg|thumb|right|A quick and dirty mining rig]]
== Introduction ==
'''Mining''' is the process of adding transaction records to Bitcoin's public ledger of past transactions.
This ledger of past transactions is called the [[block chain]] as it is a chain of [[block|blocks]].
The block chain serves to [[Confirmation|confirm]] transactions to the rest of the network as having taken place.
Bitcoin nodes use the block chain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.

Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual [[blocks]] must contain a [[proof of work|proof of work]] to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the [[hashcash]] proof-of-work function.

The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus.
Mining is also the mechanism used to introduce Bitcoins into the system:
Miners are paid any transaction fees as well as a "subsidy" of newly created coins.
This both serves the purpose of disseminating new coins in a decentralized manner as well as motivating people to provide security for the system.

Bitcoin mining is so called because it resembles the mining of other commodities:
it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.

== Difficulty ==
=== The Computationally-Difficult Problem ===
Mining a block is difficult because the SHA-256 hash of a block's header must be lower than or equal to the [[Target|target]] in order for the block to be accepted by the network. This problem can be simplified for explanation purposes: The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a [[Nonce|nonce]] is incremented. See [[Proof of work]] for more information.

=== The Difficulty Metric ===
The [[Difficulty|difficulty]] is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every 2016 blocks to a value such that the previous 2016 blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes. As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty [[Target|target]] will simply be rejected by everyone on the network and thus will be worthless.

=== Reward ===
When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks. See [[Controlled Currency Supply]].

Additionally, the miner is awarded the fees paid by users sending transactions. The fee is an incentive for the miner to include the transaction in their block. In the future, as the number of new bitcoins miners are allowed to create in each block dwindles, the fees will make up a much more important percentage of mining income.

== The mining ecosystem ==

=== Hardware ===
[[File:Usb-fpga module 1.15x-hs-800.jpg|thumb|right|FPGA Module]]
Users have used various types of hardware over time to mine blocks. Hardware specifications and performance statistics are detailed on the [[Mining Hardware Comparison]] page.
==== CPU Mining ====
Early Bitcoin client versions allowed users to use their CPUs to mine. The advent of GPU mining made CPU mining financially unwise as the hashrate of the network grew to such a degree that the amount of bitcoins produced by CPU mining became lower than the cost of power to operate a CPU. The option was therefore removed from the core Bitcoin client's user interface.

==== GPU Mining ====
GPU Mining is drastically faster and more efficient than CPU mining. See the main article: [[Why a GPU mines faster than a CPU]]. A variety of popular [[Mining rig|mining rigs]] have been documented.
==== FPGA Mining ====
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. See [[Mining Hardware Comparison]] for FPGA hardware specifications and statistics.
==== ASIC Mining ====
An application-specific integrated circuit, or ''ASIC'', is a microchip designed and manufactured for a very specific purpose. ASICs designed for Bitcoin mining were first released in 2013. For the amount of power they consume, they are vastly faster than all previous technologies and already have made GPU mining financially unwise in some countries and setups.

==== Mining services (Cloud mining) ====
[[:Category:Mining_contractors|Mining contractors]] provide mining services with performance specified by contract. They may, for example, rent out a specific level of mining capacity for a set price for a specific duration.

=== Pools ===
As more and more miners competed for the limited supply of blocks, individuals found that they were working for months without finding a block and receiving any reward for their mining efforts. This made mining something of a gamble. To address the variance in their income miners started organizing themselves into [[Pooled mining|pools]] so that they could share rewards more evenly. See [[Pooled mining]] and [[Comparison of mining pools]].

=== History ===
Bitcoin's public ledger (the 'block chain') was started on January 3rd, 2009 at 18:15 UTC presumably by [[Satoshi Nakamoto]]. The first block is known as the [[genesis block]]. The first transaction recorded in the first block was a single transaction paying the reward of 50 new bitcoins to its creator.

==See Also==

* [http://BitcoinMiner.net Comprehensive Guide Bitcoin Miner and Mining]
* [http://codinginmysleep.com/bitcoin-mining-in-plain-english Bitcoin Mining in Plain English] by David Perry
* [[Automatically mine when computer is locked|Tutorial to automatically start mining when you lock your computer]]. (Windows 7)
* [http://www.reddit.com/r/Bitcoin/comments/18q2jx/eli5_bitcoin_mining_xpost_in_eli5/ Simplified Explanation of Bitcoin Mining] by reddit user [http://www.reddit.com/user/azotic azotic]
* [http://www.vnbitcoin.org/bitcoincalculator.php Bitcoin Mining Calculator]
* [http://www.MiningContracts.com Research, Review and Compare Cloud Mining Contracts]
[[ru:Mining]]
[[Category:Mining]][[Category:Vocabulary]]

Mining

2014-07-08T20:54:31Z

Atheros: /* The mining ecosystem */ Someone accidentally a word.

[[File:Quick-and-dirty-4x5970-cooling.jpg|thumb|right|A quick and dirty mining rig]]
== Introduction ==
'''Mining''' is the process of adding transaction records to Bitcoin's public ledger of past transactions.
This ledger of past transactions is called the [[block chain]] as it is a chain of [[block|blocks]].
The block chain serves to [[Confirmation|confirm]] transactions to the rest of the network as having taken place.
Bitcoin nodes use the block chain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.

Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual [[blocks]] must contain a [[proof of work|proof of work]] to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the [[hashcash]] proof-of-work function.

The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus.
Mining is also the mechanism used to introduce Bitcoins into the system:
Miners are paid any transaction fees as well as a "subsidy" of newly created coins.
This both serves the purpose of disseminating new coins in a decentralized manner as well as motivating people to provide security for the system.

Bitcoin mining is so called because it resembles the mining of other commodities:
it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.

== Difficulty ==
=== The Computationally-Difficult Problem ===
Mining a block is difficult because the SHA-256 hash of a block's header must be lower than or equal to the [[Target|target]] in order for the block to be accepted by the network. This problem can be simplified for explanation purposes: The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a [[Nonce|nonce]] is incremented. See [[Proof of work]] for more information.

=== The Difficulty Metric ===
The [[Difficulty|difficulty]] is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every 2016 blocks to a value such that the previous 2016 blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes. As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty [[Target|target]] will simply be rejected by everyone on the network and thus will be worthless.

=== Reward ===
When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks. See [[Controlled Currency Supply]].

Additionally, the miner is awarded the fees paid by users sending transactions. The fee is an incentive for the miner to include the transaction in their block. In the future, as the number of new bitcoins miners are allowed to create in each block dwindles, the fees will make up a much more important percentage of mining income.

== The mining ecosystem ==

=== Hardware ===
[[File:Usb-fpga module 1.15x-hs-800.jpg|thumb|right|FPGA Module]]
Users have used various types of hardware over time to mine blocks. Hardware specifications and performance statistics are detailed on the [[Mining Hardware Comparison]] page.
==== CPU Mining ====
Early Bitcoin client versions allowed users to use their CPUs to mine. The advent of GPU mining made CPU mining financially unwise as the hashrate of the network grew to such a degree that the amount of bitcoins produced by CPU mining became lower than the cost of power to operate a CPU. The option was therefore removed from the core Bitcoin client's user interface.

==== GPU Mining ====
GPU Mining is drastically faster and more efficient than CPU mining. See the main article: [[Why a GPU mines faster than a CPU]]. A variety of popular [[Mining rig|mining rigs]] have been documented.
==== FPGA Mining ====
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. See [[Mining Hardware Comparison]] for FPGA hardware specifications and statistics.
==== ASIC Mining ====
An application-specific integrated circuit, or ''ASIC'', is a microchip designed and manufactured for a very specific purpose. ASICs designed for Bitcoin mining were first released in 2013. For the amount of power they consume, they are vastly faster than all previous technologies and already has made GPU mining financially unwise in some countries and setups.

==== Mining services (Cloud mining) ====
[[:Category:Mining_contractors|Mining contractors]] provide mining services with performance specified by contract. They may, for example, rent out a specific level of mining capacity for a set price for a specific duration.

=== Pools ===
As more and more miners competed for the limited supply of blocks, individuals found that they were working for months without finding a block and receiving any reward for their mining efforts. This made mining something of a gamble. To address the variance in their income miners started organizing themselves into [[Pooled mining|pools]] so that they could share rewards more evenly. See [[Pooled mining]] and [[Comparison of mining pools]].

=== History ===
Bitcoin's public ledger (the 'block chain') was started on January 3rd, 2009 at 18:15 UTC presumably by [[Satoshi Nakamoto]]. The first block is known as the [[genesis block]]. The first transaction recorded in the first block was a single transaction paying the reward of 50 new bitcoins to its creator.

==See Also==

* [http://BitcoinMiner.net Comprehensive Guide Bitcoin Miner and Mining]
* [http://codinginmysleep.com/bitcoin-mining-in-plain-english Bitcoin Mining in Plain English] by David Perry
* [[Automatically mine when computer is locked|Tutorial to automatically start mining when you lock your computer]]. (Windows 7)
* [http://www.reddit.com/r/Bitcoin/comments/18q2jx/eli5_bitcoin_mining_xpost_in_eli5/ Simplified Explanation of Bitcoin Mining] by reddit user [http://www.reddit.com/user/azotic azotic]
* [http://www.vnbitcoin.org/bitcoincalculator.php Bitcoin Mining Calculator]
* [http://www.MiningContracts.com Research, Review and Compare Cloud Mining Contracts]
[[ru:Mining]]
[[Category:Mining]][[Category:Vocabulary]]

Mining

2014-07-08T20:51:35Z

Atheros: /* Mining services (Cloud mining) */ Moved some text to the Mining contractors category where it is more relevant to keep this page shorter

[[File:Quick-and-dirty-4x5970-cooling.jpg|thumb|right|A quick and dirty mining rig]]
== Introduction ==
'''Mining''' is the process of adding transaction records to Bitcoin's public ledger of past transactions.
This ledger of past transactions is called the [[block chain]] as it is a chain of [[block|blocks]].
The block chain serves to [[Confirmation|confirm]] transactions to the rest of the network as having taken place.
Bitcoin nodes use the block chain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.

Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual [[blocks]] must contain a [[proof of work|proof of work]] to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the [[hashcash]] proof-of-work function.

The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus.
Mining is also the mechanism used to introduce Bitcoins into the system:
Miners are paid any transaction fees as well as a "subsidy" of newly created coins.
This both serves the purpose of disseminating new coins in a decentralized manner as well as motivating people to provide security for the system.

Bitcoin mining is so called because it resembles the mining of other commodities:
it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.

== Difficulty ==
=== The Computationally-Difficult Problem ===
Mining a block is difficult because the SHA-256 hash of a block's header must be lower than or equal to the [[Target|target]] in order for the block to be accepted by the network. This problem can be simplified for explanation purposes: The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a [[Nonce|nonce]] is incremented. See [[Proof of work]] for more information.

=== The Difficulty Metric ===
The [[Difficulty|difficulty]] is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every 2016 blocks to a value such that the previous 2016 blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes. As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty [[Target|target]] will simply be rejected by everyone on the network and thus will be worthless.

=== Reward ===
When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks. See [[Controlled Currency Supply]].

Additionally, the miner is awarded the fees paid by users sending transactions. The fee is an incentive for the miner to include the transaction in their block. In the future, as the number of new bitcoins miners are allowed to create in each block dwindles, the fees will make up a much more important percentage of mining income.

== The mining ecosystem ==

=== Hardware ===
[[File:Usb-fpga module 1.15x-hs-800.jpg|thumb|right|FPGA Module]]
Users have used various types of hardware over time to mine blocks. Hardware specifications and performance statistics are detailed on the [[Mining Hardware Comparison]] page.
==== CPU Mining ====
Early Bitcoin client versions allowed users to use their CPUs to mine. The advent of GPU mining made CPU mining financially unwise as the hashrate of the network grew to such a degree that the amount of bitcoins produced by CPU mining became lower than the cost of power to operate a CPU. The option was therefore removed from the core Bitcoin client's user interface.

==== GPU Mining ====
GPU Mining is drastically faster and more efficient than CPU mining. See the main article: [[Why a GPU mines faster than a CPU]]. A variety of popular [[Mining rig|mining rigs]] have been documented.
==== FPGA Mining ====
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. See [[Mining Hardware Comparison]] for FPGA hardware specifications and statistics.
==== ASIC Mining ====
An application-specific integrated circuit, or ''ASIC'', is a microchip designed and manufactured for a very specific purpose. ASICs designed for Bitcoin mining were first released in 2013. For the amount of power they consume, they are vastly faster than all previous technologies and already has made GPU mining financially unwise in some countries and setups.

==== Mining services (Cloud mining) ====
[[:Category:Mining_contractors|Mining contractors]] provide mining services with performance specified by contract. They may, for example, rent out a specific level of mining capacity for a set price for a specific duration.

=== Pools ===
As more and more miners competed for the limited supply of blocks, individuals found that they were working for months without finding a block and receiving reward for their mining efforts. This made mining something of a gamble. To address the variance in their income miners started organizing themselves into [[Pooled mining|pools]] so that they could share rewards more evenly. See [[Pooled mining]] and [[Comparison of mining pools]].

=== History ===
Bitcoin's public ledger (the 'block chain') was started on January 3rd, 2009 at 18:15 UTC presumably by [[Satoshi Nakamoto]]. The first block is known as the [[genesis block]]. The first transaction recorded in the first block was a single transaction paying the reward of 50 new bitcoins to its creator.

==See Also==

* [http://BitcoinMiner.net Comprehensive Guide Bitcoin Miner and Mining]
* [http://codinginmysleep.com/bitcoin-mining-in-plain-english Bitcoin Mining in Plain English] by David Perry
* [[Automatically mine when computer is locked|Tutorial to automatically start mining when you lock your computer]]. (Windows 7)
* [http://www.reddit.com/r/Bitcoin/comments/18q2jx/eli5_bitcoin_mining_xpost_in_eli5/ Simplified Explanation of Bitcoin Mining] by reddit user [http://www.reddit.com/user/azotic azotic]
* [http://www.vnbitcoin.org/bitcoincalculator.php Bitcoin Mining Calculator]
* [http://www.MiningContracts.com Research, Review and Compare Cloud Mining Contracts]
[[ru:Mining]]
[[Category:Mining]][[Category:Vocabulary]]

Category:Mining contractors

2014-07-08T20:50:32Z

Atheros: moved some text from the Mining article to this one

Provides mining services with performance specified by contract. For example, a specific level of mining capacity may be rented out for a set price for a specific duration. Mining shares provide Mining as a Service (MaaS). These break large-scale datacenter mining down to easily manageable pieces that are available in the form of shares of equipment.

Hosted mining services create some systemic risk for the Bitcoin system because they undermine the security assumption that the control of mining power is well distributed. If too much mining becomes consolidated in large hosting providers and an attacker is able to compromise some of these providers they could potentially disrupt the Bitcoin system or rip off people they transact with with reversals.

[[Category:Mining]]

Mining

2014-07-08T20:25:35Z

Atheros: /* CPU Mining */ rewrote sentence to fix grammar problem

[[File:Quick-and-dirty-4x5970-cooling.jpg|thumb|right|A quick and dirty mining rig]]
== Introduction ==
'''Mining''' is the process of adding transaction records to Bitcoin's public ledger of past transactions.
This ledger of past transactions is called the [[block chain]] as it is a chain of [[block|blocks]].
The block chain serves to [[Confirmation|confirm]] transactions to the rest of the network as having taken place.
Bitcoin nodes use the block chain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.

Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual [[blocks]] must contain a [[proof of work|proof of work]] to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the [[hashcash]] proof-of-work function.

The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus.
Mining is also the mechanism used to introduce Bitcoins into the system:
Miners are paid any transaction fees as well as a "subsidy" of newly created coins.
This both serves the purpose of disseminating new coins in a decentralized manner as well as motivating people to provide security for the system.

Bitcoin mining is so called because it resembles the mining of other commodities:
it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.

== Difficulty ==
=== The Computationally-Difficult Problem ===
Mining a block is difficult because the SHA-256 hash of a block's header must be lower than or equal to the [[Target|target]] in order for the block to be accepted by the network. This problem can be simplified for explanation purposes: The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a [[Nonce|nonce]] is incremented. See [[Proof of work]] for more information.

=== The Difficulty Metric ===
The [[Difficulty|difficulty]] is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every 2016 blocks to a value such that the previous 2016 blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes. As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty [[Target|target]] will simply be rejected by everyone on the network and thus will be worthless.

=== Reward ===
When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks. See [[Controlled Currency Supply]].

Additionally, the miner is awarded the fees paid by users sending transactions. The fee is an incentive for the miner to include the transaction in their block. In the future, as the number of new bitcoins miners are allowed to create in each block dwindles, the fees will make up a much more important percentage of mining income.

== The mining ecosystem ==

=== Hardware ===
[[File:Usb-fpga module 1.15x-hs-800.jpg|thumb|right|FPGA Module]]
Users have used various types of hardware over time to mine blocks. Hardware specifications and performance statistics are detailed on the [[Mining Hardware Comparison]] page.
==== CPU Mining ====
Early Bitcoin client versions allowed users to use their CPUs to mine. The advent of GPU mining made CPU mining financially unwise as the hashrate of the network grew to such a degree that the amount of bitcoins produced by CPU mining became lower than the cost of power to operate a CPU. The option was therefore removed from the core Bitcoin client's user interface.

==== GPU Mining ====
GPU Mining is drastically faster and more efficient than CPU mining. See the main article: [[Why a GPU mines faster than a CPU]]. A variety of popular [[Mining rig|mining rigs]] have been documented.
==== FPGA Mining ====
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. See [[Mining Hardware Comparison]] for FPGA hardware specifications and statistics.
==== ASIC Mining ====
An application-specific integrated circuit, or ''ASIC'', is a microchip designed and manufactured for a very specific purpose. ASICs designed for Bitcoin mining were first released in 2013. For the amount of power they consume, they are vastly faster than all previous technologies and already has made GPU mining financially unwise in some countries and setups.

==== Mining services (Cloud mining) ====
[[:Category:Mining_contractors|Mining contractors]] provide mining services with performance specified by contract. They may, for example, rent out a specific level of mining capacity for a set price for a specific duration.

Mining shares provide Mining as a Service (MaaS). These break large-scale datacenter mining down to easily manageable pieces that are available in the form of shares of equipment.

Hosted mining services create some systemic risk for the Bitcoin system because they undermine the security assumption that the control of mining power is well distributed. If too much mining becomes consolidated in large hosting providers and an attacker is able to compromise some of these providers they could potentially disrupt the Bitcoin system or rip off people they transact with with reversals.

=== Pools ===
As more and more miners competed for the limited supply of blocks, individuals found that they were working for months without finding a block and receiving reward for their mining efforts. This made mining something of a gamble. To address the variance in their income miners started organizing themselves into [[Pooled mining|pools]] so that they could share rewards more evenly. See [[Pooled mining]] and [[Comparison of mining pools]].

=== History ===
Bitcoin's public ledger (the 'block chain') was started on January 3rd, 2009 at 18:15 UTC presumably by [[Satoshi Nakamoto]]. The first block is known as the [[genesis block]]. The first transaction recorded in the first block was a single transaction paying the reward of 50 new bitcoins to its creator.

==See Also==

* [http://BitcoinMiner.net Comprehensive Guide Bitcoin Miner and Mining]
* [http://codinginmysleep.com/bitcoin-mining-in-plain-english Bitcoin Mining in Plain English] by David Perry
* [[Automatically mine when computer is locked|Tutorial to automatically start mining when you lock your computer]]. (Windows 7)
* [http://www.reddit.com/r/Bitcoin/comments/18q2jx/eli5_bitcoin_mining_xpost_in_eli5/ Simplified Explanation of Bitcoin Mining] by reddit user [http://www.reddit.com/user/azotic azotic]
* [http://www.vnbitcoin.org/bitcoincalculator.php Bitcoin Mining Calculator]
* [http://www.MiningContracts.com Research, Review and Compare Cloud Mining Contracts]
[[ru:Mining]]
[[Category:Mining]][[Category:Vocabulary]]

Mining

2014-01-13T02:32:28Z

Atheros: /* Pools */ This is not the place to discuss the virtues and vices of pools; it is only a quick introduction. Do that on the pools page.

[[File:Quick-and-dirty-4x5970-cooling.jpg|thumb|right|A quick and dirty mining rig]]
== Introduction ==
'''Mining''' is the process of adding transaction records to Bitcoin's public ledger of past transactions.
This ledger of past transactions is called the [[block chain]] as it is a chain of [[block|blocks]].
The block chain serves to [[Confirmation|confirm]] transactions to the rest of the network as having taken place.
Bitcoin nodes use the block chain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.

Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual [[blocks]] must contain a [[proof of work|proof of work]] to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the [[hashcash]] proof-of-work function.

The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus.
Mining is also the mechanism used to introduce Bitcoins into the system:
Miners are paid any transaction fees as well as a "subsidy" of newly created coins.
This both serves the purpose of disseminating new coins in a decentralized manner as well as motivating people to provide security for the system.

Bitcoin mining is so called because it resembles the mining of other commodities:
it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.

== Difficulty ==
=== The Computationally-Difficult Problem ===
Mining a block is difficult because the SHA-256 hash of a block's header must be lower than or equal to the [[Target|target]] in order for the block to be accepted by the network. This problem can be simplified for explanation purposes: The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a [[Nonce|nonce]] is incremented. See [[Proof of work]] for more information.

=== The Difficulty Metric ===
The [[Difficulty|difficulty]] is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every 2016 blocks to a value such that the previous 2016 blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes. As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty [[Target|target]] will simply be rejected by everyone on the network and thus will be worthless.

=== Reward ===
When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks. See [[Controlled Currency Supply]].

Additionally, the miner is awarded the fees paid by users sending transactions. The fee is an incentive for the miner to include the transaction in their block. In the future, as the number of new bitcoins miners are allowed to create in each block dwindles, the fees will make up a much more important percentage of mining income.

== The mining ecosystem ==

=== Hardware ===
[[File:Usb-fpga module 1.15x-hs-800.jpg|thumb|right|FPGA Module]]
Users have used various types of hardware over time to mine blocks. Hardware specifications and performance statistics are detailed on the [[Mining Hardware Comparison]] page.
==== CPU Mining ====
Early Bitcoin client versions allowed users to use their CPUs to mine. As the network hashrate grew with more power efficient GPU miners the amount of Bitcoin's produced by CPU mining became lower than the cost of power to operate the CPUS. The option still exists in the reference Bitcoin client, but it is disabled by default.

==== GPU Mining ====
GPU Mining is drastically faster and more efficient than CPU mining. See the main article: [[Why a GPU mines faster than a CPU]]. A variety of popular [[Mining rig|mining rigs]] have been documented.
==== FPGA Mining ====
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. See [[Mining Hardware Comparison]] for FPGA hardware specifications and statistics.
==== ASIC Mining ====
An application-specific integrated circuit, or ''ASIC'', is a microchip designed and manufactured for a very specific purpose. ASICs designed for Bitcoin mining were first released in 2013. For the amount of power they consume, they are vastly faster than all previous technologies and already has made GPU mining financially unwise in some countries and setups.

=== Pools ===
As more and more miners competed for the limited supply of blocks, individuals found that they were working for months without finding a block and receiving reward for their mining efforts. This made mining something of a gamble. To address the variance in their income miners started organizing themselves into [[Pooled mining|pools]] so that they could share rewards more evenly. See [[Pooled mining]] and [[Comparison of mining pools]].

=== Mining services ===
[[:Category:Mining_contractors|Mining contractors]] provide mining services with performance specified by contract. They may, for example, rent out a specific level of mining capacity for a set price for a specific duration.

Mining shares provide Mining as a Service (MaaS). These break large-scale datacenter mining down to easily manageable pieces that are available in the form of shares of equipment.

=== History ===
Bitcoin's public ledger (the 'block chain') was started on January 3rd, 2009 at 18:15 UTC presumably by [[Satoshi Nakamoto]]. The first block is known as the [[genesis block]]. The first transaction recorded in the first block was a single transaction paying the reward of 50 new bitcoins to its creator.

==See Also==

* [http://codinginmysleep.com/bitcoin-mining-in-plain-english Bitcoin Mining in Plain English] by David Perry
* [[Automatically mine when computer is locked|Tutorial to automatically start mining when you lock your computer]]. (Windows 7)
* [http://www.reddit.com/r/Bitcoin/comments/18q2jx/eli5_bitcoin_mining_xpost_in_eli5/ Simplified Explanation of Bitcoin Mining] by reddit user [http://www.reddit.com/user/azotic azotic]

[[ru:Mining]]
[[Category:Mining]][[Category:Vocabulary]]

Mining

2014-01-13T02:31:55Z

Atheros: /* The mining ecosystem */ Made article more neutral by linking to category pages instead of specific company pages.

[[File:Quick-and-dirty-4x5970-cooling.jpg|thumb|right|A quick and dirty mining rig]]
== Introduction ==
'''Mining''' is the process of adding transaction records to Bitcoin's public ledger of past transactions.
This ledger of past transactions is called the [[block chain]] as it is a chain of [[block|blocks]].
The block chain serves to [[Confirmation|confirm]] transactions to the rest of the network as having taken place.
Bitcoin nodes use the block chain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.

Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual [[blocks]] must contain a [[proof of work|proof of work]] to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the [[hashcash]] proof-of-work function.

The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus.
Mining is also the mechanism used to introduce Bitcoins into the system:
Miners are paid any transaction fees as well as a "subsidy" of newly created coins.
This both serves the purpose of disseminating new coins in a decentralized manner as well as motivating people to provide security for the system.

Bitcoin mining is so called because it resembles the mining of other commodities:
it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.

== Difficulty ==
=== The Computationally-Difficult Problem ===
Mining a block is difficult because the SHA-256 hash of a block's header must be lower than or equal to the [[Target|target]] in order for the block to be accepted by the network. This problem can be simplified for explanation purposes: The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a [[Nonce|nonce]] is incremented. See [[Proof of work]] for more information.

=== The Difficulty Metric ===
The [[Difficulty|difficulty]] is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every 2016 blocks to a value such that the previous 2016 blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes. As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty [[Target|target]] will simply be rejected by everyone on the network and thus will be worthless.

=== Reward ===
When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks. See [[Controlled Currency Supply]].

Additionally, the miner is awarded the fees paid by users sending transactions. The fee is an incentive for the miner to include the transaction in their block. In the future, as the number of new bitcoins miners are allowed to create in each block dwindles, the fees will make up a much more important percentage of mining income.

== The mining ecosystem ==

=== Hardware ===
[[File:Usb-fpga module 1.15x-hs-800.jpg|thumb|right|FPGA Module]]
Users have used various types of hardware over time to mine blocks. Hardware specifications and performance statistics are detailed on the [[Mining Hardware Comparison]] page.
==== CPU Mining ====
Early Bitcoin client versions allowed users to use their CPUs to mine. As the network hashrate grew with more power efficient GPU miners the amount of Bitcoin's produced by CPU mining became lower than the cost of power to operate the CPUS. The option still exists in the reference Bitcoin client, but it is disabled by default.

==== GPU Mining ====
GPU Mining is drastically faster and more efficient than CPU mining. See the main article: [[Why a GPU mines faster than a CPU]]. A variety of popular [[Mining rig|mining rigs]] have been documented.
==== FPGA Mining ====
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. See [[Mining Hardware Comparison]] for FPGA hardware specifications and statistics.
==== ASIC Mining ====
An application-specific integrated circuit, or ''ASIC'', is a microchip designed and manufactured for a very specific purpose. ASICs designed for Bitcoin mining were first released in 2013. For the amount of power they consume, they are vastly faster than all previous technologies and already has made GPU mining financially unwise in some countries and setups.

=== Pools ===
As more and more miners competed for the limited supply of blocks, individuals found that they were working for months without finding a block and receiving reward for their mining efforts. This made mining something of a gamble. To address the variance in their income miners started organizing themselves into [[Pooled mining|pools]] so that they could share rewards more evenly. See [[Pooled mining]] and [[Comparison of mining pools]].

Similar to cloud mining traditional mining pools also create some potentially risky consolidation of control over hashing power. Although the individual miners are free to move to other pools if a pool misbehaves it can take days for them to notice misbehavior and react. Decentralized mining pools such as [[P2Pool]] exist to eliminate this risk but are more complicated to use.

=== Mining services ===
[[:Category:Mining_contractors|Mining contractors]] provide mining services with performance specified by contract. They may, for example, rent out a specific level of mining capacity for a set price for a specific duration.

Mining shares provide Mining as a Service (MaaS). These break large-scale datacenter mining down to easily manageable pieces that are available in the form of shares of equipment.

=== History ===
Bitcoin's public ledger (the 'block chain') was started on January 3rd, 2009 at 18:15 UTC presumably by [[Satoshi Nakamoto]]. The first block is known as the [[genesis block]]. The first transaction recorded in the first block was a single transaction paying the reward of 50 new bitcoins to its creator.

==See Also==

* [http://codinginmysleep.com/bitcoin-mining-in-plain-english Bitcoin Mining in Plain English] by David Perry
* [[Automatically mine when computer is locked|Tutorial to automatically start mining when you lock your computer]]. (Windows 7)
* [http://www.reddit.com/r/Bitcoin/comments/18q2jx/eli5_bitcoin_mining_xpost_in_eli5/ Simplified Explanation of Bitcoin Mining] by reddit user [http://www.reddit.com/user/azotic azotic]

[[ru:Mining]]
[[Category:Mining]][[Category:Vocabulary]]

Wallet import format

2013-12-06T22:32:17Z

Atheros:

Wallet Import Format (WIF, also known as Wallet Export Format) is a way of encoding a private ECDSA key so as to make it easier to copy.

A testing suite is available for encoding and decoding of WIF at:

http://gobittest.appspot.com/PrivateKey

==Private key to WIF==
1 - Take a private key
0C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D
2 - Add a 0x80 byte in front of it for mainnet addresses or 0xef for testnet addresses
800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D
3 - Perform SHA-256 hash on the extended key
8147786C4D15106333BF278D71DADAF1079EF2D2440A4DDE37D747DED5403592
4 - Perform SHA-256 hash on result of SHA-256 hash
507A5B8DFED0FC6FE8801743720CEDEC06AA5C6FCA72B07C49964492FB98A714
5 - Take the first 4 bytes of the second SHA-256 hash, this is the checksum
507A5B8D
6 - Add the 4 checksum bytes from point 5 at the end of the extended key from point 2
800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D507A5B8D
7 - Convert the result from a byte string into a base58 string using [[Base58Check encoding]]. This is the Wallet Import Format
5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ

==WIF to private key==
1 - Take a Wallet Import Format string
5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ
2 - Convert it to a byte string using [[Base58Check encoding]]
800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D507A5B8D
3 - Drop the last 4 checksum bytes from the byte string
800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D
4 - Drop the first byte (it should be 0x80). This is the private key
0C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D
==WIF checksum checking==
1 - Take the Wallet Import Format string
5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ
2 - Convert it to a byte string using [[Base58Check encoding]]
800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D507A5B8D
3 - Drop the last 4 checksum bytes from the byte string
800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D
3 - Perform SHA-256 hash on the shortened string
8147786C4D15106333BF278D71DADAF1079EF2D2440A4DDE37D747DED5403592
4 - Perform SHA-256 hash on result of SHA-256 hash
507A5B8DFED0FC6FE8801743720CEDEC06AA5C6FCA72B07C49964492FB98A714
5 - Take the first 4 bytes of the second SHA-256 hash, this is the checksum
507A5B8D
6 - Make sure it is the same, as the last 4 bytes from point 2
507A5B8D
7 - If they are, and the byte string from point 2 starts with 0x80 (0xef for testnet addresses), then there is no error.

{{Stub}}

Foreign exchange markets

2013-12-03T21:40:27Z

Atheros: Created page with "(empty page in anticipation of page edits by a different user)"

(empty page in anticipation of page edits by a different user)

Abe

2013-07-24T20:11:45Z

Atheros:

[[File:penny-abe-160.png|thumb|160px|Abe]]

'''Abe''' is a free, open-source [[block chain browser]] released by [[User:JohnTobey253|John Tobey]] under the [[wikipedia:Affero General Public License|Affero General Public License]].

Written in [[wikipedia:Python (programming language)|Python]] and portable [[wikipedia:SQL|SQL]],<ref>https://bitcointalk.org/index.php?topic=16141.0</ref> Abe draws inspiration from [[Bitcoin Block Explorer]] and seeks some level of compatibility with it but uses a completely new implementation.<ref>https://raw.github.com/jtobey/bitcoin-abe/master/README.md</ref>

==See Also==

* [[Block chain browser]]

== External Links ==

* [http://abe.john-edwin-tobey.org/ Original demonstration site]
* [https://bitcointalk.org/index.php?topic=22785.0 Project announcement]
* [https://github.com/jtobey/bitcoin-abe Project on Github]

==References==
<references />

[[Category:Block chain browsers]]
[[Category:Free Software]]
[[Category:Open Source]]

Časté otázky

2013-07-24T20:08:22Z

Atheros:

Na tomto mieste nájdete odpovede na najčastejšie kladené otázky.

== Všeobecné ==
=== Čo sú to bitcoiny? ===
Bitcoiny sú menové jednotky  systému Bitcoin. Zaužívaná skratka je “BTC” pri cenách alebo množstvách (napríklad “100 BTC”).
Existujú aj [[physical bitcoins|fyzické bitcoiny]], ale v konečnom dôsledku je bitcoin len číslo priradené k [[Address|bitcoinovej adrese]]. Fyzický bitcoin je objekt, napríklad minca, v ktorom je toto číslo ukryté.  Pozri aj [[Úvod|jednoduchý úvod]] do bitcoinu.

=== Ako môžem získať bitcoiny? ===

Existuje niekoľko spôsobov, ako získať bitcoiny:

* Prijímajte bitcoiny ako platbu za tovary alebo služby.
* Existujú viaceré služby, kde sa bitcoiny dajú [[buying bitcoins|kúpiť]] za tradičné meny
* Nájdite si miestneho obchodníka na [http://tradebitcoin.com tradebitcoin] (alebo niekde inde) a zameňte s ním hotovosť
* Vytvorte nový [[block|blok]] (momentálne je odmena 50 bitcoinov)
* Zapojte sa do [[Pooled mining|zdieľanej ťažby (pooled mining)]]

=== Garantuje Bitcoin prísun peňazí zadarmo? ===

Bitcoin je nová technológia, a preto nemusí byť celkom jasné, čo to presne je a ako to funguje. Bitcoin je občas prezentovaný ako niektoré z nasledovného:
'''A)''' Internetový podvod lákajúci ľudí vidinou rýchleho zbohatnutia
'''B)''' Diera v trhovej ekonomike, ktorej fungovanie zabezpečí stabilný príjem
'''C)''' Bezpečná investícia, ktorá takmer určite prinesie zisk

V skutočnosti nič z toho nie je pravda. 
=== Dajú sa bitcoiny kúpiť pomocou PayPal-u? ===
Fyzické bitcoiny sa dajú kúpiť pomocou PayPal-u. Oveľa ťažšie je kúpiť digitálne bitcoiny s PayPal-om kvôli riziku, že predajca bude reklamovať a žiadať peniaze naspäť. Predaj fyzických vecí je menej riskantný ako predaj digitálnych vecí.

Aj keď sa dajú nájsť ľudia ochotní predať Vám bitcoiny cez PayPal (napríklad na [http://www.bitcoin-otc.com/ #bitcoin-otc] ), väčšina veľkých búrz nepovoľuje platby cez PayPal. Dôvodom sú opakované prípady, keď podvodník zaplatí za bitcoiny cez PayPal, obdrží bitcoiny a potom sa sťažuje, že tovar nedostal. PayPal dosť často dáva za pravdu takýmto podvodníkom, a preto burzy už nedovoľujú tento spôsob platby.

Aj tak je možné kúpiť bitcoiny od jednotlivcov, ale v tomto prípade je potrebná vzájomná dôvera a predajca bitcoinov by si mal dávať pozor.

=== Where can I find a forum of Bitcoin users? ===

There is no longer an "official" forum for Bitcoin. The [[Bitcoin:Community_portal#Bitcoin_Community_Forums_on_various_platforms|Community Portal]] includes links to some forums.

=== How are new Bitcoins created? ===

[[File:total_bitcoins_over_time_graph.png|thumb|Number of bitcoins over time, assuming a perfect 10-minute interval.]]
New coins are generated by a network node each time it finds the solution to a certain mathematical problem (i.e. creates a new [[block]]), which is difficult to perform and can demonstrate a [[proof of work]]. The reward for solving a block is [[Controlled Currency Supply|automatically adjusted]] so that in the first 4 years of the Bitcoin network, 10,500,000 BTC will be created. The amount is halved each 4 years, so it will be 5,250,000 over years 4-8, 2,625,000 over years 8-12 and so on. Thus the total number of bitcoins in existence will not exceed 21,000,000. See [[Controlled Currency Supply]].

Blocks are [[Mining|generated]] every 10 minutes, on average. As the number of people who attempt to generate these new coins changes, the difficulty of creating new coins changes. This happens in a manner that is agreed upon in advance by the network as a whole, based upon the time taken to generate the previous 2016 blocks. The difficulty is therefore related to the average computing resources devoted to generate these new coins over the time it took to create these previous blocks. The likelihood of somebody creating a block is based on the calculation speed of the system that they are using compared to the aggregate calculation speed of all the other systems generating blocks on the network. See [[Mining]].

=== What's the current total number of Bitcoins in existence? ===

[http://blockexplorer.com/q/totalbc Current count]. Also see [https://blockchain.info/charts/total-bitcoins Total Bitcoins in circulation chart]

The number of blocks times the coin value of a block is the number of coins in existence. The coin value of a block is 50 BTC for each of the first 210,000 blocks, 25 BTC for the next 210,000 blocks, then 12.5 BTC, 6.25 BTC and so on.

=== How divisible are Bitcoins? ===

Technically, a Bitcoin can be divided down to 8 decimals using existing data structures, so 0.00000001 BTC is the smallest amount currently possible. Discussions about and ideas for ways to provide for even smaller quantities of Bitcoins may be created in the future if the need for them ever arises.

=== What do I call the various denominations of Bitcoins? ===

There is a lot of discussion about the naming of these fractions of Bitcoins. The leading candidates are:

* 1 BTC = 1 Bitcoin
* 0.01 BTC = 1 cBTC = 1 Centi-Bitcoin (also referred to as Bitcent)
* 0.001 BTC = 1 mBTC = 1 Milli-Bitcoin (also referred to as mbit (pronounced em-bit) or millibit)
* 0.000 001 BTC = 1 μBTC = 1 Micro-Bitcoin (also referred to as ubit (pronounced yu-bit) or microbit)

The above follows the accepted international SI units for thousandths, millionths and billionths. There are many arguments against the special case of 0.01 BTC since it is unlikely to represent anything meaningful as the Bitcoin economy grows (it certainly won't be the equivalent of 0.01 USD, GBP or EUR). Equally, the inclusion of existing national currency denominations such as "cent", "nickel", "dime", "pence", "pound", "kopek" and so on are to be discouraged. This is a worldwide currency.

One exception is the "satoshi" which is smallest denomination currently possible

* 0.000 000 01 BTC = 1 Satoshi (pronounced sa-toh-shee)

which is so named in honour of Satoshi Nakamoto the pseudonym of the inventor of Bitcoin.

For an overview of all defined units of Bitcoin (including less common and niche units), see [[Units]].

Further discussion on this topic can be found on the forums here:

* [http://forum.bitcoin.org/index.php?topic=14438.msg195287#msg195287 We need names]
* [http://forum.bitcoin.org/index.php?topic=8282.0 What to call 0.001 BTC]

=== How does the halving work when the number gets really small? ===

The reward will go from 0.00000001 BTC to 0. Then no more coins will likely be created.

The calculation is done as a right bitwise shift of a 64-bit signed integer, which means it is divided by 2 and rounded down. The integer is equal to the value in BTC * 100,000,000. This is how all Bitcoin balances/values are stored internally.

Keep in mind that using current rules this will take nearly 100 years before it becomes an issue and Bitcoins may change considerably before that happens.

=== How long will it take to generate all the coins? ===

The last block that will generate coins will be block #6,929,999. This should be generated around year 2140. Then the total number of coins in circulation will remain static at 20,999,999.9769 BTC.

Even if the allowed precision is expanded from the current 8 decimals, the total BTC in circulation will always be slightly below 21 million (assuming everything else stays the same). For example, with 16 decimals of precision, the end total would be 20999999.999999999496 BTC.

=== If no more coins are going to be generated, will more blocks be created? ===

Absolutely! Even before the creation of coins ends, the use of [[transaction fee|transaction fees]] will likely make creating new blocks more valuable from the fees than the new coins being created. When coin generation ends, what will sustain the ability to use bitcoins will be these fees entirely. There will be blocks generated after block #6,929,999.

=== But if no more coins are generated, what happens when Bitcoins are lost? Won't that be a problem? ===

Because of the law of supply and demand, when fewer bitcoins are available the ones that are left will be in higher demand, and therefore will have a higher value. So, as Bitcoins are lost, the remaining bitcoins will eventually increase in value to compensate. As the value of a bitcoin increases, the number of bitcoins required to purchase an item '''de'''creases. This is a [[Deflationary spiral|deflationary economic model]]. As the average transaction size reduces, transactions will probably be denominated in sub-units of a bitcoin such as millibitcoins ("Millies") or microbitcoins ("Mikes").

The Bitcoin protocol uses a base unit of one hundred-millionth of a Bitcoin ("a Satoshi"), but unused bits are available in the protocol fields that could be used to denote even smaller subdivisions.

=== If every transaction is broadcast via the network, does Bitcoin scale? ===
The Bitcoin protocol allows lightweight clients that can use Bitcoin without downloading the entire transaction history. As traffic grows and this becomes more critical, implementations of the concept will be developed. Full network nodes will at some point become a more specialized service.

With some modifications to the software, full Bitcoin nodes could easily keep up with both VISA and MasterCard combined, using only fairly modest hardware (a couple of racks of machines using todays hardware). It's worth noting that the MasterCard network is structured somewhat like Bitcoin itself - as a peer to peer broadcast network.

Learn more about [[Scalability]].

==Economy==
=== Where does the value of Bitcoin stem from? What backs up Bitcoin? ===
Bitcoins have value because they are useful and because they are [[Controlled Currency Supply|scarce]]. As they are accepted by more merchants, their value will [http://en.wikipedia.org/wiki/Sticky_%28economics%29 stabilize]. See the [[Trade|list of Bitcoin-accepting sites]].

When we say that a currency is backed up by gold, we mean that there's a promise in place that you can exchange the currency for gold. Bitcoins, like dollars and euros, are not backed up by anything except the variety of merchants that accept them.

It's a common misconception that Bitcoins gain their value from the cost of electricity required to generate them. Cost doesn't equal value – hiring 1,000 men to shovel a big hole in the ground may be costly, but not valuable. Also, even though scarcity is a critical requirement for a useful currency, it alone doesn't make anything valuable. For example, your fingerprints are scarce, but that doesn't mean they have any exchange value.

=== Is Bitcoin a bubble? ===
Yes, in the same way as the euro and dollar are. They only have value in exchange and have no inherent value. If everyone suddenly stopped accepting your dollars, euros or bitcoins, the "bubble" would burst and their value would drop to zero. But that is unlikely to happen: even in Somalia, where the government collapsed 20 years ago, [http://en.wikipedia.org/wiki/Somali_shilling Somali shillings] are still accepted as payment.

=== Is Bitcoin a Ponzi scheme? ===
In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. Early adopters can only profit at the expense of late adopters. Bitcoin has possible win-win outcomes. Early adopters profit from the rise in value. Late adopters, and indeed, society as a whole, benefit from the usefulness of a stable, fast, inexpensive, and widely accepted p2p currency.

The fact that early adopters benefit more doesn't alone make anything a Ponzi scheme. All good investments in successful companies have this quality.

=== Doesn't Bitcoin unfairly benefit early adopters? ===
Early adopters have a large number of bitcoins now because they took a risk and invested resources in an unproven technology. By so doing, they have helped Bitcoin become what it is now and what it will be in the future (hopefully, a ubiquitous decentralized digital currency). It is only fair they will reap the benefits of their successful investment.

In any case, any bitcoin generated will probably change hands dozens of time as a medium of exchange, so the profit made from the initial distribution will be insignificant compared to the total commerce enabled by Bitcoin.

Since the pricing of Bitcoins has fallen greatly from its June 2011 peak, prices today are much more similar to those enjoyed by many early adopters. Those who are buying Bitcoins today likely believe that Bitcoin will grow significantly in the future. Setting aside the brief opportunity to have sold Bitcoins at the June 2011 peak enjoyed by few, the early-adopter window is arguably still open.

===Won't loss of wallets and the finite amount of Bitcoins create excessive deflation, destroying Bitcoin? ===
Worries about Bitcoin being destroyed by deflation are not entirely unfounded. Unlike most currencies, which experience inflation as their founding institutions create more and more units, Bitcoin will likely experience gradual deflation with the passage of time. Bitcoin is unique in that only a small amount of units will ever be produced (twenty-one million to be exact), this number has been known since the project's inception, and the units are created at a predicable rate.

Also, Bitcoin users are faced with a danger that doesn't threaten users of any other currency: if a Bitcoin user loses his wallet, his money is gone forever, unless he finds it again. And not just to him; it's gone completely out of circulation, rendered utterly inaccessible to anyone. As people will lose their wallets, the total number of Bitcoins will slowly decrease.

Therefore, Bitcoin seems to be faced with a unique problem. Whereas most currencies inflate over time, Bitcoin will mostly likely do the just the opposite. Time will see the irretrievable loss of an ever-increasing number of Bitcoins. An already small number will be permanently whittled down further and further. And as there become fewer and fewer Bitcoins, the laws of supply and demand suggest that their value will probably continually rise.

Thus Bitcoin is bound to once again stray into mysterious territory, because no one exactly knows what happens to a currency that grows continually more valuable. Economists generally agree that a low level of inflation is a good thing for a currency, but nobody is quite sure about what might happens to one that continually deflates. Although deflation could hardly be called a rare phenomenon, steady, constant deflation is unheard of. There may be a lot of speculation, no one has any hard data to back up their claims.

That being said, there is a mechanism in place to combat the obvious consequences. Extreme deflation would render most currencies highly impractical: if a single Canadian dollar could suddenly buy the holder a car, how would one go about buying bread or candy? Even pennies would fetch more than a person could carry. Bitcoin, however, offers a simple and stylish solution: infinite divisibility. Bitcoins can be divided up and trade into as small of pieces as one wants, so no matter how valuable Bitcoins become, one can trade them in practical quantities.

In fact, infinite divisibility should allow Bitcoins to function in cases of extreme wallet loss. Even if, in the far future, so many people have lost their wallets that only a single Bitcoin, or a fraction of one, remains, Bitcoin should continue to function just fine. No one can claim to be sure what is going to happen, but deflation may prove to present a smaller threat than many expect.

For more information, see the [[Deflationary spiral]] page.

=== What if someone bought up all the existing Bitcoins? ===
Bitcoin markets are competitive -- meaning the price of a bitcoin will rise or fall depending on supply and demand at certain price levels. Only a fraction of bitcoins issued to date are found on the exchange markets for sale. So even though technically a buyer with lots of money could buy all the bitcoins offered for sale, unless those holding the rest of the bitcoins offer them for sale as well, even the wealthiest, most determined buyer can't get at them.

Additionally, new currency continues to be issued daily and will continue to do so for decades though over time the rate at which they are issued declines to insignificant levels. Those who are mining aren't obligated to sell their bitcoins so not all bitcoins will make it to the markets even.

This situation doesn't suggest, however, that the markets aren't vulnerable to price manipulation. It doesn't take significant amounts of money to move the market price up or down and thus Bitcoin remains a volatile asset.

===What if someone creates a new block chain, or a new digital currency that renders Bitcoin obsolete?===

That the block chain cannot be easily forked represents one of the central security mechanisms of Bitcoin. Given the choice between two block chains, a Bitcoin miner always chooses the longer one - that is to say, the one with the more complex hash. Thusly, it ensures that each user can only spend their bitcoins once, and that no user gets ripped off.

As a consequence of the block chain structure, there may at any time be many different sub-branches, and the possibility always exists of a transaction being over-written by the longest branch, if it has been recorded in a shorter one. The older a transaction is though, the lower its chances of being over-written, and the higher of becoming permanent. Although the block chain prevents one from spending more Bitcoins than one has, it means that transactions can be accidentally nullified.

A new block chain would leave the network vulnerable to [[double-spending|double-spend]] attacks. However, the creation of a viable new chain presents considerable difficulty, and the possibility does not present much of a risk.

Bitcoin will always choose the longer Block Chain and determines the relative length of two branches by the complexities of their hashes. Since the hash of each new block is made from that of the block preceding it, to create a block with a more complex hash, one must be prepared to do more computation than has been done by the entire Bitcoin network from the fork point up to the newest of the blocks one is trying to supersede. Needless to say, such an undertaking would require a very large amount of processing power and since Bitcoin is continually growing and expanding, it will likely only require more with the passage of time.

A much more distinct and real threat to the Bitcoin use is the development of other, superior virtual currencies, which could supplant Bitcoin and render it obsolete and valueless.

A great deal of careful thought and ingenuity has gone into the development of Bitcoin, but it is the first of its breed, a prototype, and vulnerable to more highly-evolved competitors. At present, any threatening rivals have yet to rear its head; Bitcoin remains the first and foremost private virtual currency, but we can offer no guarantees that it will retain that position. It would certainly be in keeping with internet history for similar system built from the same principles to supersede and cast Bitcoin into obsolescence, after time had revealed its major shortcomings. Friendster and Myspace suffered similar fates at the hand of Facebook, Napster was ousted by Limeware, Bearshare and torrent applications, and Skype has all but crushed the last few disciples of the Microsoft Messenger army.

This may sound rather foreboding, so bear in mind that introduction of new and possibly better virtual currencies will not necessarily herald Bitcoin's demise. If Bitcoin establishes itself sufficiently firmly before the inception of the next generation of private, online currencies as to gain widespread acceptance and general stability, future currencies may pose little threat even if they can claim superior design.

==Sending and Receiving Payments==

=== Why do I have to wait 10 minutes before I can spend money I received? ===

10 minutes is the average time taken to find a block. It can be significantly more or less time than that depending on luck; 10 minutes is simply the average case.

[[Blocks]] (shown as "confirmations" in the GUI) are how the Bitcoin achieves consensus on who owns what. Once a block is found everyone agrees that you now own those coins, so you can spend them again. Until then it's possible that some network nodes believe otherwise, if somebody is attempting to defraud the system by reversing a transaction. The more confirmations a transaction has, the less risk there is of a reversal. Only 6 blocks or 1 hour is enough to make reversal computationally impractical. This is dramatically better than credit cards which can see chargebacks occur up to three months after the original transaction!

Ten minutes was specifically chosen by [[Satoshi]] as a tradeoff between propagation time of new blocks in large networks and the amount of work wasted due to chain splits. For a more technical explanation, see Satoshi's [http://www.bitcoin.org/bitcoin.pdf original technical paper].

[[File:TransactionConfirmationTimesExample.PNG]]

=== Do you have to wait until my transactions are confirmed in order to buy or sell things with Bitcoin? ===

YES, you do, IF the transaction is non-recourse. The Bitcoin reference software does not display transactions as confirmed until six blocks have passed (confirmations). As transactions are burred in the chain they become increasingly non-reversible but are very reversible before the first confirmation. Two to six confirmations are recommended for non-recourse situations depending on the value of the transactions involved.

When people ask this question they are usually thinking about applications like supermarkets. This generally is a recourse situation: if somebody tries to double-spend on a face-to-face transaction it might work a few times, but probabalistically speaking eventually one of the double-spends will get noticed, and the penalty for shoplifting charges in most localities is calibrated to be several times worse than the proceeds of a single shoplifting event.

Double-spends might be a concern for something like a snack machine in a low-traffic area with no nearby security cameras. Such a machine shouldn't honor 0-confirmation payments, and should instead use some other mechanism of clearing Bitcoin or validating transactions against reversal, see the wiki article [[Myths#Point_of_sale_with_bitcoins_isn.27t_possible_because_of_the_10_minute_wait_for_confirmation|here]] for alternatives.

When people ask this question they are usually thinking about applications that require immediate payment processing, like supermarkets or snack machines. Here is one way to reverse an unconfirmed payment:

A [[Double-spending#Finney_attack|Finney attack]], in which an attacker mines a block containing a movement of some coins back to themselves. Once they find a block solution, they quickly go to a merchant and make a purchase, then broadcast the block, thus taking back the coins. This attack is a risk primarily for goods that are dispatched immediately, like song downloads or currency trades. Because the attacker can't choose the time of the attack, it isn't a risk for merchants such as supermarkets where you can't choose exactly when to pay (due to queues, etc). The attack can fail if somebody else finds a block containing the purchasing transaction before you release your own block, therefore, merchants can reduce but not eliminate the risk by making purchasers wait some length of time that's less than a confirm.

Because pulling off this attack is not trivial, merchants who need to sell things automatically and instantly are most likely to just price the cost of reversal fraud in, or use insurance.

=== I was sent some bitcoins and they haven't arrived yet! Where are they? ===

Don't panic! There are a number of reasons why your bitcoins might not show up yet, and a number of ways to diagnose them.

The latest version of the Bitcoin-Qt client will tell you how far it has to go yet in downloading the blockchain. Hover over the icon in the bottom right corner of the client to learn your client's status.

If it has not caught up then it's possible that your transaction hasn't been included in a block yet.

You can check pending transactions in the network by going [http://blockchain.info here] and then searching for your address. If the transaction is listed here then it's a matter of waiting until it gets included in a block before it will show in your client.

Bear in mind that if the transaction is based on a coin that was in a recent transaction then it could be considered a low priority transaction take longer to transfer if the transaction fee paid isn't high enough. Very low priority transactions with 0 fees might take hours or days to be included in a block.

=== Why does my Bitcoin address keep changing? ===

Whenever the address listed in "Your address" receives a transaction, Bitcoin replaces it with a new address. This is meant to encourage you to use a new address for every transaction, which enhances [[anonymity]]. All of your old addresses are still usable: you can see them in ''Settings -> Your Receiving Addresses''.

===How much will the transaction fee be?===

Some transactions might require a [[transaction fee]] for them to get confirmed in a timely manner. The transaction fee is processed by and received by the bitcoin miner. The most recent version of the Bitcoin client will estimate an appropriate fee when a fee might be required.

The fee is added to the payment amount. For example, if you are sending a 1.234 BTC payment and the client requires a 0.0005 BTC fee, then 1.2345 BTC will be subtracted from the wallet balance for the entire transaction and the address for where the payment was sent will receive a payment of 1.234 BTC.

In cases where a fee is required it is required because your transaction objectively looks like a denial of service attack to the bitcoin system, either due to it being burdensome to transmit or it recycles bitcoins you recently received. The wallet software attempts to avoid generating burdensome transactions, but it isn't always able if the funds in your wallet are new or are composed of many very tiny payments.

Because the fee is related to the amount of data that makes up the transaction and not to the amount of bitcoins being sent, the fee may seem extremely low (0.0005 BTC for a 1,000 BTC transfer) or unfairly high (0.004 BTC for a 0.02 BTC payment, or about 20%). If you are receiving tiny amounts (e.g., as small payments from a mining pool) then fees when sending will be higher than if your activity follows a more normal consumer or business transaction pattern. As of bitcoin 0.5.3 the required fee it will ask for will not be higher than 0.05 BTC, though for most users there is usually no required fee at all and 0.0005 is the most common when one is required.

=== What happens when someone sends me a bitcoin but my computer is powered off? ===

Bitcoins aren't actually "sent" to your wallet, the software only uses that term so that we can use the currency without having to learn new concepts. Your wallet is only needed when you wish to spend coins that you've received.

The coins that were sent to you when the client was not running will later appear as if they were received in your wallet when you later launch the client. It will download blocks and catch up with any transactions it didn't already have.

=== How long does "synchronizing" take when the bitcoin client is first installed? What is it doing? ===

The popular bitcoin client software from bitcoin.org implements a "full" bitcoin node: It can carry out all the duties of the bitcoin P2P system, it isn't simply a "client". One of the principles behind the operation of full bitcoin nodes is that they don't trust that the other participants have followed the rules of the bitcoin system. During synchronization the software is processing historical bitcoin transactions and making sure for itself that all of the rules of the system have been correctly followed.

In normal operation after synchronizing the software should use a hardly noticeable amount of IO, CPU, or network capacity.

The initial validation is very disk IO intensive so the amount of time to synchronize depend on your disk speed and, to a lesser extent, your cpu speed. It can take anywhere from a few hours to a day or so. You can use the software while this process is going on, but you may not see recent payments to you until the synchronization has caught up to the point where those transactions happened.

If this is too long for you, you can download a pre-synchronized blockchain from [http://eu1.bitcoincharts.com/blockchain/ http://eu1.bitcoincharts.com/blockchain/]. Alternatively, you can try an alternative "lite" client such as Multibit or a super-light client like electrum though these clients have somewhat weaker security, are less mature, and don't contribute to the health of the P2P network.

==Networking==
=== Do I need to configure my firewall to run bitcoin? ===

Bitcoin will connect to other nodes, usually on tcp port 8333. You will need to allow outgoing TCP connections to port 8333 if you want to allow your bitcoin client to connect to many nodes. [[Testnet]] uses tcp port 18333 instead of 8333.

If you want to restrict your firewall rules to a few ips, you can find stable nodes in the [[Fallback Nodes|fallback nodes list]].

=== How does the peer finding mechanism work? ===

Bitcoin finds peers primarily by forwarding peer announcements within its own network and each node saves a database of peers that it's aware of for use in the future. In order to bootstrap this process Bitcoin needs a list of initial peers, these can be provided manually but normally it obtains them by querying a set of DNS domain names which have automatically updated lists, if that doesn't work it falls back to a build-in list which is updated from time to time in new versions of the software. There is also an IRC based mechanism but it is disabled by default.

==Mining==
===What is mining?===
[[Mining]] is the process of spending computation power to secure Bitcoin transactions against reversal and introducing new Bitcoins to the system.

Technically speaking, mining is the calculation of a [[hash]] of the a block header, which includes among other things a reference to the previous block, a hash of a set of transactions and a [[nonce]]. If the hash value is found to be less than the current [[target]] (which is inversely proportional to the [[difficulty]]), a new block is formed and the miner gets the newly generated Bitcoins (50 per block at current levels). If the hash is not less than the current target, a new nonce is tried, and a new hash is calculated. This is done millions of times per second by each miner.

===Is mining used for some useful computation?===
The computations done when mining are internal to Bitcoin and not related to any other distributed computing projects. They serve the purpose of securing the Bitcoin network, which is useful.

===Is it not a waste of energy?===
Spending energy on creating and securing a free monetary system is hardly a waste. Also, services necessary for the operation of currently widespread monetary systems, such as banks and credit card companies, also spend energy, arguably more than Bitcoin would.

===Why don't we use calculations that are also useful for some other purpose?===
To provide security for the Bitcoin network, the calculations involved need to have some very specific features. These features are incompatible with leveraging the computation for other purposes.

===How does the proof-of-work system help secure Bitcoin?===
To give a general idea of the mining process, imagine this setup:

payload = <some data related to things happening on the Bitcoin network>
nonce = 1
hash = [http://en.wikipedia.org/wiki/SHA2 SHA2]( [http://en.wikipedia.org/wiki/SHA2 SHA2]( payload + nonce ) )

The work performed by a miner consists of repeatedly increasing "nonce" until
the hash function yields a value, that has the rare property of being below a certain
target threshold. (In other words: The hash "starts with a certain number of zeroes",
if you display it in the fixed-length representation, that is typically used.)

As can be seen, the mining process doesn't compute anything special. It merely
tries to find a number (also referred to as nonce) which - in combination with the payload -
results in a hash with special properties.

The advantage of using such a mechanism consists of the fact, that it is very easy to check a result: Given
the payload and a specific nonce, only a single call of the hashing function
is needed to verify that the hash has the required properties. Since there is no
known way to find these hashes other than brute force, this can be used as a "proof of work"
that someone invested a lot of computing power to find the correct nonce for this payload.

This feature is then used in the Bitcoin network to secure various aspects. An attacker
that wants to introduce malicious payload data into the network, will need to do the
required proof of work before it will be accepted. And as long as honest miners have more
computing power, they can always outpace an attacker.

Also see [http://en.wikipedia.org/wiki/SHA2 SHA2] and [http://en.wikipedia.org/wiki/Proof-of-work_system Proof-of-work system] on Wikipedia.

===Why was the "Generate coin" option of the client software removed?===

In the early days of Bitcoin, it was easy for anyone to find new blocks using standard CPUs. As more and more people started mining, the [[difficulty]] of finding new blocks has greatly increased to the point where the average time for a CPU to find a single block can be many years. The only cost-effective method of [[Mining|mining]] is using a high-end graphics card with special software (see also [[Why a GPU mines faster than a CPU]]) and/or joining a [[Bitcoin Pool|mining pool]]. Since solo CPU mining is essentially useless, it was removed from the GUI of the Bitcoin software.

==Security==

===Could miners collude to give themselves money or to fundamentally change the nature of Bitcoin?===

There are two questions in here. Let's look at them separately.

'''Could miners gang up and give themselves money?'''

Mining itself is the process of creating new blocks in the block chain. Each block contains a list of all the transactions that have taken place across the entire Bitcoin network since the last block was created, as well as a hash of the previous block. New blocks are 'mined', or rather, generated, by Bitcoin clients correctly guessing sequences of characters in codes called 'hashes,' which are created using information from previous blocks. Bitcoin users may download specialized 'mining' software, which allows them to dedicate some amount of their processing power – however large or small – to guessing at strings within the hash of the previous block. Whoever makes the right guess first, thus creating a new block, receives a reward in Bitcoins.

The block chain is one of the two structures that makes Bitcoin secure, the other being the public-key encryption system on which Bitcoin trade is based. The block chain assures that not only is every single transaction that ever takes place recorded, but that every single transaction is recorded on the computer of anyone who chooses to store the relevant information. Many, many users have complete records of every transaction in Bitcoins history readily available to them at any point, and anyone who wants in the information can obtain it with ease. These things make Bitcoin very hard to fool.

The Bitcoin network takes considerable processing power to run, and since those with the most processing power can make the most guesses, those who put the most power toward to sustaining the network earn the most currency. Each correct guess yields, at present, fifty Bitcoins, and as Bitcoins are presently worth something (although the value still fluctuates) every miner who earns any number of Bitcoins makes money. Some miners pull in Bitcoins on their own; and some also join or form pools wherein all who contribute earn a share of the profits.

Therefore, first answer is a vehement “yes” – no only can miners collude to get more money, Bitcoin is designed to encourage them to do so. Bitcoin pools are communal affairs, and there is nothing dishonest or underhanded about them.

Of course, the real question is:

'''Can they do so in ways not sanction by Bitcoin developers? Is there any way to rip off the network and make loads of money dishonestly?'''

Bitcoin isn't infallible. It can be cheated. But doing so is extremely difficult. Bitcoin was designed to evade some of the central problems with modern currencies – namely, that their trustworthiness hinges upon that of people who might not have user's best interests in mind. Every currency in the world (other than Bitcoin) is controlled by large institutions who keep track of what's done with done with it, and who can manipulate it's value. And every other currency has value because people trust the institutions that control them.

Bitcoin doesn't ask that it users trust any institution. Its security is based on the cryptography that is an integral part of its structure, and that is readily available for any and all to see. Instead of one entity keeping track of transactions, the entire network does, so Bitcoins are astoundingly difficult to steal, or double-spend. Bitcoins are created in a regular and predictable fashion, and by many different users, so no one can decide to make a whole lot more and lessen their value. In short, Bitcoin is designed to be inflation-proof, double-spend-proof and completely distributed.

Nonetheless, there are a few ways that one can acquire Bitcoins dishonestly. Firstly, one can steal private keys. Key theft isn't something that Bitcoin security has been designed to prevent: it's up to users to keep their's safe. But the cryptography is designed so that it is completely impossible to deduce someone's private from their public one. So long as you keep your private key to yourself, you don't have much to worry about. Furthermore, one could theoretically create a new block chain, but due to the way in which the block chain is constructed, this would be extremely difficult and require massive amounts of processing power. A full explanation of the difficulties involved can be found in the [[block chain]] article.

Bitcoin can be ripped off – but doing so would be extremely hard and require considerable expertise and a staggering amount of processing power. And it's only going to get harder with the passage of time. Bitcoin is isn't impenetrable, but it's close enough to put any real worries in the peripherals.

'''Could miners fundamentally change the nature of Bitcoin?'''

Once again, almost certainly not.

Bitcoin is a distributed network, so any changes implemented to the system must be accepted by all users. Someone trying to change the way Bitcoins are generated would have to convince every user to download and use their software – so the only changes that would go through are those that would be equally benefit all users.

And thus, it is more or less impossible for any person to change the function of Bitcoin to their advantage. If users don't like the changes, they won't take, and if uses do like them, then they'll help everyone equally. Of course, one can conceive of a situation where someone manages to get a change pushed through that provides them with an advantage that no one notices, but given that Bitcoin is structurally relatively simple, it is unlikely that any major changes will go through without someone noticing first.

The fact that such changes are so difficult to make testifies to the fully distributed nature of Bitcoin. Any centrally-controlled currency can be modified by its central agency without the consent of its adherents. Bitcoin has no central authority, so it changes only at the behest of the whole community. Bitcoins development represents a kind of collective evolution; the first of its kind among currencies.

==Help==
===I'd like to learn more. Where can I get help?===

* Read the [[Introduction|introduction to bitcoin]]
* See the videos, podcasts, and blog posts from the [[Press]]
* Read and post on the [[Bitcoin:Community_portal#Bitcoin_Community_Forums|forums]]
* Chat on one of the [[Bitcoin:Community_portal#IRC_Chat|Bitcoin IRC]] channels
* Listen to [http://omegataupodcast.net/2011/03/59-bitcoin-a-digital-decentralized-currency/ this podcast], which goes into the details of how bitcoin works
* Ask questions on the [http://bitcoin.stackexchange.com Bitcoin Stack Exchange]

==See Also==

* [[Man page]]
* [[Introduction]]

[[de:FAQ]]
[[zh-cn:FAQ]]
[[fr:FAQ]]
[[ru:FAQ]]

[[Category:Technical]]
[[Category:Vocabulary]]

Help:FAQ

2013-07-24T20:07:49Z

Atheros:

Here you will find answers to the most commonly asked questions.

== General ==
=== What are bitcoins? ===
Bitcoins are the unit of currency of the Bitcoin system. A commonly used shorthand for this is “BTC” to refer to a price or amount (eg: “100 BTC”).
There are such things as [[physical bitcoins]], but ultimately, a bitcoin is just a number associated with a [[Address|Bitcoin Address]]. A physical bitcoin is simply an object, such as a coin, with the number carefully embedded inside. See also an [[Introduction|easy intro]] to bitcoin.

=== How can I get bitcoins? ===

There are a variety of ways to acquire bitcoins:

* Accept bitcoins as payment for goods or services.
* The most common way to buy bitcoins are the [[Buying bitcoins|Bitcoin Exchanges]]
* There are several services where you can [[Buying_Bitcoins_(the_noob_version)|trade them]] for traditional currency.
* Find someone to trade cash for bitcoins in-person through a [https://en.bitcoin.it/wiki/Category:Directories local directory].
* Participate in a [[Pooled mining|mining pool]].
* If you have a lot of mining hardware, you can solo mine and attempt to create a new [[block]] (currently yields 25 bitcoins plus transaction fees).
* Visit sites that provide [[Trade#Free_Samples_and_Offers|free samples and offers]].

===Does Bitcoin guarantee an influx of free money?===

Since Bitcoin is a new technology, what it is and how it works may be initially unclear. Bitcoin is sometimes presented as being one of three things:
<ol style="list-style-type: upper-alpha;">
<li>Some sort of online 'get-rich-quick' scam.</li>
<li>A loophole in the market economy, the installation of which guarantees a steady influx of cash.</li>
<li>A sure investment that will almost certainly yield a profit.</li>
</ol>
In fact, none of the above are true. Let's look at them independently.

;Is Bitcoin a 'get-rich-quick' scheme?
:If you've spent much time on the Internet, you've probably seen ads for many 'get-rich-quick' schemes. These ads usually promise huge profits for a small amounts of easy work. Such schemes are usually pyramid/matrix-style schemes that make money from their own employees and offer nothing of any real value. Most convince one to buy packages that will make them earn hundreds a day, which in fact have the buyer distribute more such ads, and make minute profits.

:Bitcoin is in no way similar to these schemes. Bitcoin doesn't promise windfall profits. There is no way for the developers to make money from your involvement or to take money from you. That bitcoins are nearly impossible to acquire without the owner's consent represents one of its greatest strengths. Bitcoin is an experimental, virtual currency that may succeed or may fail. None of its developers expect to get rich off of it.

:A more detailed answer to this question can be found [http://bitcointalk.org/?topic=7815.0 here].

;Will I make money by installing the client?
:Most people who use Bitcoin don't earn anything by doing so, and the default client has no built-in way to earn Bitcoins. A small minority of people with dedicated, high-performance hardware do earn some Bitcoins by "''mining''" (generating new bitcoins, see [[#What is mining?|What is mining?]]) with special software, but joining Bitcoin shouldn't be construed as being the road to riches. Most Bitcoin users get involved because they find the project conceptually interesting and don't earn anything by doing so. This is also why you won't find much speculation about the political or economic repercussions of Bitcoin anywhere on this site: Bitcoin developers owe their dedication to the project's intellectual yieldings more than to those of a monetary nature. Bitcoin is still taking its first baby steps; it may go on to do great things but right now it only has something to offer those chasing conceptually interesting projects or bleeding edge technology.

;As an investment, is Bitcoin a sure thing?
:Bitcoin is a new and interesting electronic currency, the value of which is not backed by any single government or organization. Like other currencies, it is worth something partly because people are willing to trade it for goods and services. Its exchange rate fluctuates continuously, and sometimes wildly. It lacks wide acceptance and is vulnerable to manipulation by parties with modest funding. Security incidents such as website and account compromise may trigger major sell-offs. Other fluctuations can build into positive feedback loops and cause much larger exchange rate fluctuations. Anyone who puts money into Bitcoin should understand the risk they are taking and consider it a high-risk currency. Later, as Bitcoin becomes better known and more widely accepted, it may stabilize, but for the time being it is unpredictable. Any investment in Bitcoin should be done carefully and with a clear plan to manage the risk.

=== Can I buy bitcoins with Paypal? ===

It is possible to buy [[physical bitcoins]] with PayPal but it is otherwise difficult and/or expensive to do so for non-physical bitcoins, because of significant risk to the seller.

While it is possible to find an individual who wishes to sell Bitcoin to you via Paypal, (perhaps via [http://www.bitcoin-otc.com/ #bitcoin-otc] ) most exchanges do not allow funding through PayPal. This is due to repeated cases where someone pays for bitcoins with Paypal, receives their bitcoins, and then fraudulently complains to Paypal that they never received their purchase. PayPal often sides with the fraudulent buyer in this case, which means any seller needs to cover that risk with higher fees or refuse to accept PayPal altogether.

Buying Bitcoins from individuals this way is still possible, but requires the seller to have some trust that the buyer will not file a claim with PayPal to reverse the payment.

=== Where can I find a forum to discuss Bitcoin? ===

Please visit the [[Bitcoin:Community_portal#Bitcoin_Community_Forums_on_various_platforms|Community Portal]] for links to Bitcoin-related forums.

=== How are new bitcoins created? ===

[[File:total_bitcoins_over_time_graph.png|thumb|Number of bitcoins over time, assuming a perfect 10-minute interval.]]
New bitcoins are generated by the network through the process of "[[#What is mining?|''mining'']]". In a process that is similar to a continuous raffle draw, mining nodes on the network are awarded bitcoins each time they find the solution to a certain mathematical problem (and thereby create a new [[block]]). Creating a block is a [[proof of work]] with a difficulty that varies with the overall strength of the network. The reward for solving a block is [[Controlled Currency Supply|automatically adjusted]] so that roughly every four years of operation of the Bitcoin network, half the amount of bitcoins created in the prior 4 years are created. {{formatnum:10500000}} bitcoins were created in the first 4 (approx.) years from January 2009 to November 2012. Every four years thereafter this amount halves, so it will be {{formatnum:5250000}} over years 4-8, {{formatnum:2625000}} over years 8-12, and so on. Thus the total number of bitcoins in existence will never exceed {{formatnum:21000000}}. See [[Controlled Currency Supply]].

Blocks are [[Mining|mined]] every 10 minutes, on average and for the first four years ({{formatnum:210000}} blocks) each block included 50 new bitcoins. As the amount of processing power directed at mining changes, the difficulty of creating new bitcoins changes. This difficulty factor is calculated every 2016 blocks and is based upon the time taken to generate the previous 2016 blocks. See [[Mining]].

=== What's the current total number of bitcoins in existence? ===

[http://blockexplorer.com/q/totalbc Current count]. Also see [https://blockchain.info/charts/total-bitcoins Total bitcoins in circulation chart]

The number of blocks times the coin value of a block is the number of coins in existence. The coin value of a block is 50 BTC for each of the first {{formatnum:210000}} blocks, 25 BTC for the next {{formatnum:210000}} blocks, then 12.5 BTC, 6.25 BTC and so on.

=== How divisible are bitcoins? ===

A bitcoin can be divided down to 8 decimal places. Therefore, 0.00000001 BTC is the smallest amount that can be handled in a transaction. If necessary, the protocol and related software can be modified to handle even smaller amounts.

=== What do I call the various denominations of bitcoin? ===

There is a lot of discussion about the naming of these fractions of bitcoins. The leading candidates are:

* 1 BTC = 1 bitcoin
* 0.01 BTC = 1 cBTC = 1 centibitcoin (also referred to as bitcent)
* 0.001 BTC = 1 mBTC = 1 millibitcoin (also referred to as mbit (pronounced em-bit) or millibit or even bitmill)
* 0.000 001 BTC = 1 μBTC = 1 microbitcoin (also referred to as ubit (pronounced yu-bit) or microbit)

The above follows the accepted international SI prefixes for hundredths, thousandths, and millionths. There are many arguments against the special case of 0.01 BTC since it is unlikely to represent anything meaningful as the Bitcoin economy grows (it certainly won't be the equivalent of 0.01 USD, GBP or EUR). Equally, the inclusion of existing national currency denominations such as "cent", "nickel", "dime", "pence", "pound", "kopek" and so on are to be discouraged; this is a worldwide currency.

One exception is the "satoshi" which is smallest denomination currently possible

* 0.000 000 01 BTC = 1 satoshi (pronounced sa-toh-shee)
which is so named in honour of Satoshi Nakamoto, the pseudonym of the inventor of Bitcoin.

For an overview of all defined units of Bitcoin (including less common and niche units), see [[Units]].

Further discussion on this topic can be found on the forums here:

* [https://bitcointalk.org/index.php?topic=14438.msg195287#msg195287 We need names]
* [https://bitcointalk.org/index.php?topic=8282.0 What to call 0.001 BTC]

=== How does the halving work when the number gets really small? ===

Eventually the reward will go from 0.00000001 BTC to zero and no more bitcoins will be created.

The block reward calculation is done as a right bitwise shift of a 64-bit signed integer, which means it is divided by two and rounded down. The integer is equal to the value in BTC * 100,000,000 since internally in the reference client software, all Bitcoin balances and values are stored as unsigned integers.

With an initial block reward of 50 BTC, it will take many 4-year periods for the block reward to reach zero.

=== How long will it take to generate all the coins? ===

The last block that will generate coins will be block #6,929,999 which should be generated at or near the year 2140. The total number of coins in circulation will then remain static at 20,999,999.9769 BTC.

Even if the allowed precision is expanded from the current 8 decimals, the total BTC in circulation will always be slightly below 21 million (assuming everything else stays the same). For example, with 16 decimals of precision, the end total would be 20,999,999.999999999496 BTC.

=== If no more coins are going to be generated, will more blocks be created? ===

Absolutely! Even before the creation of coins ends, the use of [[transaction fee|transaction fees]] will likely make creating new blocks more valuable from the fees than the new coins being created. When coin generation ends, these fees will sustain the ability to use bitcoins and the Bitcoin network. There is no practical limit on the number of blocks that will be mined in the future.

=== But if no more coins are generated, what happens when Bitcoins are lost? Won't that be a problem? ===

Because of the law of supply and demand, when fewer bitcoins are available the ones that are left will be in higher demand, and therefore will have a higher value. So, as Bitcoins are lost, the remaining bitcoins will eventually increase in value to compensate. As the value of a bitcoin increases, the number of bitcoins required to purchase an item '''de'''creases. This is a [[Deflationary spiral|deflationary economic model]]. As the average transaction size reduces, transactions will probably be denominated in sub-units of a bitcoin such as millibitcoins ("Millies") or microbitcoins ("Mikes").

The Bitcoin protocol uses a base unit of one hundred-millionth of a Bitcoin ("a Satoshi"), but unused bits are available in the protocol fields that could be used to denote even smaller subdivisions.

=== If every transaction is broadcast via the network, does Bitcoin scale? ===
The Bitcoin protocol allows lightweight clients that can use Bitcoin without downloading the entire transaction history. As traffic grows and this becomes more critical, implementations of the concept will be developed. Full network nodes will at some point become a more specialized service.

With some modifications to the software, full Bitcoin nodes could easily keep up with both VISA and MasterCard combined, using only fairly modest hardware (a single high end server by todays standards). It is worth noting that the MasterCard network is structured somewhat like Bitcoin itself - as a peer to peer broadcast network.

Learn more about [[Scalability]].

==Economy==
=== Where does the value of Bitcoin stem from? What backs up Bitcoin? ===
Bitcoins have value because they are useful and because they are [[Controlled Currency Supply|scarce]]. As they are accepted by more merchants, their value will [http://en.wikipedia.org/wiki/Sticky_%28economics%29 stabilize]. See the [[Trade|list of Bitcoin-accepting sites]].

When we say that a currency is backed up by gold, we mean that there's a promise in place that you can exchange the currency for gold. Bitcoins, like dollars and euros, are not backed up by anything except the variety of merchants that accept them.

It's a common misconception that Bitcoins gain their value from the cost of electricity required to generate them. Cost doesn't equal value – hiring 1,000 men to shovel a big hole in the ground may be costly, but not valuable. Also, even though scarcity is a critical requirement for a useful currency, it alone doesn't make anything valuable. For example, your fingerprints are scarce, but that doesn't mean they have any exchange value.

Alternatively it needs to be added that while the law of supply and demand applies it does not guarantee value of Bitcoins in the future. If confidence in Bitcoins is lost then it will not matter that the supply can no longer be increased, the demand will fall off with all holders trying to get rid of their coins. An example of this can be seen in cases of state currencies, in cases when the state in question dissolves and so no new supply of the currency is available (the central authority managing the supply is gone), however the demand for the currency falls sharply because confidence in its purchasing power disappears. Of-course Bitcoins do not have such central authority managing the supply of the coins, but it does not prevent confidence from eroding due to other situations that are not necessarily predictable.

=== Is Bitcoin a bubble? ===
Yes, in the same way as the euro and dollar are. They only have value in exchange and have no inherent value. If everyone suddenly stopped accepting your dollars, euros or bitcoins, the "bubble" would burst and their value would drop to zero. But that is unlikely to happen: even in Somalia, where the government collapsed 20 years ago, [http://en.wikipedia.org/wiki/Somali_shilling Somali shillings] are still accepted as payment.

=== Is Bitcoin a Ponzi scheme? ===
In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. Early adopters can only profit at the expense of late adopters. Bitcoin has possible win-win outcomes. Early adopters profit from the rise in value. Late adopters, and indeed, society as a whole, benefit from the usefulness of a stable, fast, inexpensive, and widely accepted p2p currency.

The fact that early adopters benefit more doesn't alone make anything a Ponzi scheme. All good investments in successful companies have this quality.

=== Doesn't Bitcoin unfairly benefit early adopters? ===
Early adopters have a large number of bitcoins now because they took a risk and invested resources in an unproven technology. By so doing, they have helped Bitcoin become what it is now and what it will be in the future (hopefully, a ubiquitous decentralized digital currency). It is only fair they will reap the benefits of their successful investment.

In any case, any bitcoin generated will probably change hands dozens of time as a medium of exchange, so the profit made from the initial distribution will be insignificant compared to the total commerce enabled by Bitcoin.

Since the pricing of Bitcoins has fallen greatly from its June 2011 peak, prices today are much more similar to those enjoyed by many early adopters. Those who are buying Bitcoins today likely believe that Bitcoin will grow significantly in the future. Setting aside the brief opportunity to have sold Bitcoins at the June 2011 peak enjoyed by few, the early-adopter window is arguably still open.

===Won't loss of wallets and the finite amount of Bitcoins create excessive deflation, destroying Bitcoin? ===
Worries about Bitcoin being destroyed by deflation are not entirely unfounded. Unlike most currencies, which experience inflation as their founding institutions create more and more units, Bitcoin will likely experience gradual deflation with the passage of time. Bitcoin is unique in that only a small amount of units will ever be produced (twenty-one million to be exact), this number has been known since the project's inception, and the units are created at a predictable rate.

Also, Bitcoin users are faced with a danger that doesn't threaten users of any other currency: if a Bitcoin user loses his wallet, his money is gone forever, unless he finds it again. And not just to him; it's gone completely out of circulation, rendered utterly inaccessible to anyone. As people will lose their wallets, the total number of Bitcoins will slowly decrease.

Therefore, Bitcoin seems to be faced with a unique problem. Whereas most currencies inflate over time, Bitcoin will mostly likely do just the opposite. Time will see the irretrievable loss of an ever-increasing number of Bitcoins. An already small number will be permanently whittled down further and further. And as there become fewer and fewer Bitcoins, the laws of supply and demand suggest that their value will probably continually rise.

Thus Bitcoin is bound to once again stray into mysterious territory, because no one exactly knows what happens to a currency that grows continually more valuable. Many economists claim that a low level of inflation is a good thing for a currency, but nobody is quite sure about what might happens to one that continually deflates. Although deflation could hardly be called a rare phenomenon, steady, constant deflation is unheard of. There may be a lot of speculation, no one has any hard data to back up their claims.

That being said, there is a mechanism in place to combat the obvious consequences. Extreme deflation would render most currencies highly impractical: if a single Canadian dollar could suddenly buy the holder a car, how would one go about buying bread or candy? Even pennies would fetch more than a person could carry. Bitcoin, however, offers a simple and stylish solution: infinite divisibility. Bitcoins can be divided up and trade into as small of pieces as one wants, so no matter how valuable Bitcoins become, one can trade them in practical quantities.

In fact, infinite divisibility should allow Bitcoins to function in cases of extreme wallet loss. Even if, in the far future, so many people have lost their wallets that only a single Bitcoin, or a fraction of one, remains, Bitcoin should continue to function just fine. No one can claim to be sure what is going to happen, but deflation may prove to present a smaller threat than many expect.

For more information, see the [[Deflationary spiral]] page.

=== What if someone bought up all the existing Bitcoins? ===
Bitcoin markets are competitive -- meaning the price of a bitcoin will rise or fall depending on supply and demand at certain price levels. Only a fraction of bitcoins issued to date are found on the exchange markets for sale. So even though technically a buyer with lots of money could buy all the bitcoins offered for sale, unless those holding the rest of the bitcoins offer them for sale as well, even the wealthiest, most determined buyer can't get at them.

Additionally, new currency continues to be issued daily and will continue to do so for decades though over time the rate at which they are issued declines to insignificant levels. Those who are mining aren't obligated to sell their bitcoins so not all bitcoins will make it to the markets even.

This situation doesn't suggest, however, that the markets aren't vulnerable to price manipulation. It doesn't take significant amounts of money to move the market price up or down and thus Bitcoin remains a volatile asset.

===What if someone creates a new block chain, or a new digital currency that renders Bitcoin obsolete?===

That the block chain cannot be easily forked represents one of the central security mechanisms of Bitcoin. Given the choice between two block chains, a Bitcoin miner always chooses the longer one - that is to say, the one with the more complex hash. Thusly, it ensures that each user can only spend their bitcoins once, and that no user gets ripped off.

As a consequence of the block chain structure, there may at any time be many different sub-branches, and the possibility always exists of a transaction being over-written by the longest branch, if it has been recorded in a shorter one. The older a transaction is though, the lower its chances of being over-written, and the higher of becoming permanent. Although the block chain prevents one from spending more Bitcoins than one has, it means that transactions can be accidentally nullified.

A new block chain would leave the network vulnerable to [[double-spending|double-spend]] attacks. However, the creation of a viable new chain presents considerable difficulty, and the possibility does not present much of a risk.

Bitcoin will always choose the longer Block Chain and determines the relative length of two branches by the complexities of their hashes. Since the hash of each new block is made from that of the block preceding it, to create a block with a more complex hash, one must be prepared to do more computation than has been done by the entire Bitcoin network from the fork point up to the newest of the blocks one is trying to supersede. Needless to say, such an undertaking would require a very large amount of processing power and since Bitcoin is continually growing and expanding, it will likely only require more with the passage of time.

A much more distinct and real threat to the Bitcoin use is the development of other, superior virtual currencies, which could supplant Bitcoin and render it obsolete and valueless.

A great deal of careful thought and ingenuity has gone into the development of Bitcoin, but it is the first of its breed, a prototype, and vulnerable to more highly-evolved competitors. At present, any threatening rivals have yet to rear their heads; Bitcoin remains the first and foremost private virtual currency, but we can offer no guarantees that it will retain that position. It would certainly be in keeping with internet history for a similar system built from the same principles to supersede and cast Bitcoin into obsolescence, after time had revealed its major shortcomings. Friendster and Myspace suffered similar fates at the hand of Facebook, Napster was ousted by Limeware, Bearshare and torrent applications, and Skype has all but crushed the last few disciples of the Microsoft Messenger army.

This may sound rather foreboding, so bear in mind that the introduction of new and possibly better virtual currencies will not necessarily herald Bitcoin's demise. If Bitcoin establishes itself sufficiently firmly before the inception of the next generation of private, online currencies so as to gain widespread acceptance and general stability, future currencies may pose little threat even if they can claim superior design. This is known as the network effect.

=== Is Bitcoin open to value manipulation? ===

The current low market cap of Bitcoin means that any investor with deep enough pockets can significantly change/manipulate the rate. Is this a problem?

This is only a problem if you are investing in Bitcoin for short period of time. A manipulator can't change the fundamentals, and over a period of 5-10 years they will win over any short term manipulations.

==Sending and Receiving Payments==

=== Why do I have to wait 10 minutes before I can spend money I received? ===

10 minutes is the average time taken to find a block. It can be significantly more or less time than that depending on luck; 10 minutes is simply the average case.

[[Blocks]] (shown as "confirmations" in the GUI) are how the Bitcoin achieves consensus on who owns what. Once a block is found everyone agrees that you now own those coins, so you can spend them again. Until then it's possible that some network nodes believe otherwise, if somebody is attempting to defraud the system by reversing a transaction. The more confirmations a transaction has, the less risk there is of a reversal. Only 6 blocks or 1 hour is enough to make reversal computationally impractical. This is dramatically better than credit cards which can see chargebacks occur up to three months after the original transaction!

Ten minutes was specifically chosen by [[Satoshi]] as a tradeoff between first confirmation time and the amount of work wasted due to chain splits. After a block is mined, it takes time for other miners to find out about it, and until then they are actually competing against the new block instead of adding to it. If someone mines another new block based on the old block chain, the network can only accept one of the two, and all the work that went into the other block gets wasted. For example, if it takes miners 1 minute on average to learn about new blocks, and new blocks come every 10 minutes, then the overall network is wasting about 10% of its work. Lengthening the time between blocks reduces this waste.

As a thought experiment, what if the Bitcoin network grew to include Mars? From the farthest points in their orbits, it takes about 20 minutes for a signal to travel from Earth to Mars. With only 10 minutes between new blocks, miners on Mars would always be 2 blocks behind the miners on Earth. It would be almost impossible for them to contribute to the block chain. If we wanted collaborate with those kinds of delays, we would need at least a few hours between new blocks.

[[File:TransactionConfirmationTimesExample.PNG]]

=== Do you have to wait until my transactions are confirmed in order to buy or sell things with Bitcoin? ===

YES, you do, IF the transaction is non-recourse. The Bitcoin reference software does not display transactions as confirmed until six blocks have passed (confirmations). As transactions are burred in the chain they become increasingly non-reversible but are very reversible before the first confirmation. Two to six confirmations are recommended for non-recourse situations depending on the value of the transactions involved.

When people ask this question they are usually thinking about applications like supermarkets. This generally is a recourse situation: if somebody tries to double-spend on a face-to-face transaction it might work a few times, but probabalistically speaking eventually one of the double-spends will get noticed, and the penalty for shoplifting charges in most localities is calibrated to be several times worse than the proceeds of a single shoplifting event.

Double-spends might be a concern for something like a snack machine in a low-traffic area with no nearby security cameras. Such a machine shouldn't honor 0-confirmation payments, and should instead use some other mechanism of clearing Bitcoin or validating transactions against reversal, see the wiki article [[Myths#Point_of_sale_with_bitcoins_isn.27t_possible_because_of_the_10_minute_wait_for_confirmation|here]] for alternatives.

Applications that require immediate payment processing, like supermarkets or snack machines, need to manage the risks. Here is one way to reverse an unconfirmed payment:

A [[Double-spending#Finney_attack|Finney attack]], in which an attacker mines a block containing a movement of some coins back to themselves. Once they find a block solution, they quickly go to a merchant and make a purchase, then broadcast the block, thus taking back the coins. This attack is a risk primarily for goods that are dispatched immediately, like song downloads or currency trades. Because the attacker can't choose the time of the attack, it isn't a risk for merchants such as supermarkets where you can't choose exactly when to pay (due to queues, etc). The attack can fail if somebody else finds a block containing the purchasing transaction before you release your own block, therefore, merchants can reduce but not eliminate the risk by making purchasers wait some length of time that's less than a confirm.

Because pulling off this attack is not trivial, merchants who need to sell things automatically and instantly are most likely to just price the cost of reversal fraud in, or use insurance.

=== I was sent some bitcoins and they haven't arrived yet! Where are they? ===

Don't panic! There are a number of reasons why your bitcoins might not show up yet, and a number of ways to diagnose them.

The latest version of the Bitcoin-Qt client tells you how far it has yet to go in downloading the blockchain. Hover over the icon in the bottom right corner of the client to learn your client's status.

If it has not caught up then it's possible that your transaction hasn't been included in a block yet.

You can check pending transactions in the network by going [http://blockchain.info here] and then searching for your address. If the transaction is listed here then it's a matter of waiting until it gets included in a block before it will show in your client.

If the transaction is based on a coin that was in a recent transaction then it could be considered a low priority transaction. Transfers can take longer if the transaction fee paid was not high enough. If there is no fee at all the transfer can get a very low priority and take hours or even days to be included in a block.

=== Why does my Bitcoin address keep changing? ===

Whenever the address listed in "Your address" receives a transaction, Bitcoin replaces it with a new address. This is meant to encourage you to use a new address for every transaction, which enhances [[anonymity]]. All of your old addresses are still usable: you can see them in ''Settings -> Your Receiving Addresses''.

===How much will the transaction fee be?===

Some transactions might require a [[transaction fee]] for them to get confirmed in a timely manner. The transaction fee is processed by and received by the bitcoin miner. The most recent version of the Bitcoin client will estimate an appropriate fee when a fee might be required.

The fee is added to the payment amount. For example, if you are sending a 1.234 BTC payment and the client requires a 0.0005 BTC fee, then 1.2345 BTC will be subtracted from the wallet balance for the entire transaction and the address for where the payment was sent will receive a payment of 1.234 BTC.

A fee might be imposed because your transaction looks like a denial of service attack to the Bitcoin system. For example, it might be burdensome to transmit or it might recycle Bitcoins you recently received. The wallet software attempts to avoid generating burdensome transactions, but it isn't always able to do so: The funds in your wallet might be new or composed of many tiny payments.

Because the fee is related to the amount of data that makes up the transaction and not to the amount of Bitcoins being sent, the fee may seem extremely low (0.0005 BTC for a 1,000 BTC transfer) or unfairly high (0.004 BTC for a 0.02 BTC payment, or about 20%). If you are receiving tiny amounts (''e.g.'' as small payments from a mining pool) then fees when sending will be higher than if your activity follows the pattern of conventional consumer or business transactions.

As of Bitcoin 0.5.3 the required fee will not be higher than 0.05 BTC. For most users there is usually no required fee at all. If a fee is required it will most commonly be 0.0005 BTC.

=== What happens when someone sends me a bitcoin but my computer is powered off? ===

Bitcoins are not actually "sent" to your wallet; the software only uses that term so that we can use the currency without having to learn new concepts. Your wallet is only needed when you wish to spend coins that you've received.

If you are sent coins when your wallet client program is not running, and you later launch the wallet client program, the coins will eventually appear as if they were just received in the wallet. That is to say, when the client program is started it must download blocks and catch up with any transactions it did not already know about.

=== How long does "synchronizing" take when the Bitcoin client is first installed? What's it doing? ===

The popular Bitcoin client software from bitcoin.org implements a "full" Bitcoin node: It can carry out all the duties of the Bitcoin P2P system, it isn't simply a "client". One of the principles behind the operation of full Bitcoin nodes is that they don't assume that the other participants have followed the rules of the Bitcoin system. During synchronization, the software is processing historical Bitcoin transactions and making sure for itself that all of the rules of the system have been correctly followed.

In normal operation, after synchronizing, the software should use a hardly noticeable amount of your computer's resources.

When the wallet client program is first installed, its initial validation requires a lot of work from your computer's hard disk, so the amount of time to synchronize depends on your disk speed and, to a lesser extent, your CPU speed. It can take anywhere from a few hours to a day or so. On a slow computer it could take more than 40 hours of continuous synchronization, so check your computer's power-saving settings to ensure that it does not turn its hard disk off when unattended for a few hours. You can use the Bitcoin software during synchronization, but you may not see recent payments to you until the client program has caught up to the point where those transactions happened.

If you feel that this process takes too long, you can download a pre-synchronized blockchain from [http://eu2.bitcoincharts.com/blockchain/ http://eu2.bitcoincharts.com/blockchain/]. Alternatively, you can try an alternative "lite" client such as Multibit or a super-light client like electrum, though these clients have somewhat weaker security, are less mature, and don't contribute to the health of the P2P network.

==Networking==
=== Do I need to configure my firewall to run Bitcoin? ===

Bitcoin will connect to other nodes, usually on TCP port 8333. You will need to allow outgoing TCP connections to port 8333 if you want to allow your Bitcoin client to connect to many nodes. [[Testnet]] uses TCP port 18333 instead of 8333.

If you want to restrict your firewall rules to a few IPs, you can find stable nodes in the [[Fallback Nodes|fallback nodes list]].

=== How does the peer finding mechanism work? ===

Bitcoin finds peers primarily by forwarding peer announcements within its own network and each node saves a database of peers that it's aware of, for future use. In order to bootstrap this process Bitcoin needs a list of initial peers, these can be provided manually but normally it obtains them by querying a set of DNS domain names which have automatically updated lists, if that doesn't work it falls back to a built-in list which is updated from time to time in new versions of the software. There is also an IRC based mechanism but it is disabled by default.

==Mining==
===What is mining?===
[[Mining]] is the process of spending computation power to secure Bitcoin transactions against reversal and introducing new Bitcoins to the system.

Technically speaking, mining is the calculation of a [[hash]] of the a block header, which includes among other things a reference to the previous block, a hash of a set of transactions and a [[nonce]]. If the hash value is found to be less than the current [[target]] (which is inversely proportional to the [[difficulty]]), a new block is formed and the miner gets the newly generated Bitcoins (25 per block at current levels). If the hash is not less than the current target, a new nonce is tried, and a new hash is calculated. This is done millions of times per second by each miner.

===Is mining used for some useful computation?===
The computations done when mining are internal to Bitcoin and not related to any other distributed computing projects. They serve the purpose of securing the Bitcoin network, which is useful.

===Is it not a waste of energy?===
Spending energy on creating and securing a free monetary system is hardly a waste. Also, services necessary for the operation of currently widespread monetary systems, such as banks and credit card companies, also spend energy, arguably more than Bitcoin would.

===Why don't we use calculations that are also useful for some other purpose?===
To provide security for the Bitcoin network, the calculations involved need to have some [http://bitcoin.stackexchange.com/questions/5617/why-are-bitcoin-calculation-useless/5618#5618 very specific features]. These features are incompatible with leveraging the computation for other purposes.

===How can we stop miners from creating zero transaction blocks?===
The incentive for miners to include transactions is in the fees that come along with them. If we were to implement some minimum number of transactions per block it would be trivial for a miner to create and include transactions merely to surpass that threshold. As the network matures, the block reward drops, and miners become more dependent on transactions fees to pay their costs, the problem of zero transaction blocks should diminish over time.

===How does the proof-of-work system help secure Bitcoin?===
To give a general idea of the mining process, imagine this setup:

payload = <some data related to things happening on the Bitcoin network>
nonce = 1
hash = [http://en.wikipedia.org/wiki/SHA2 SHA2]( [http://en.wikipedia.org/wiki/SHA2 SHA2]( payload + nonce ) )

The work performed by a miner consists of repeatedly increasing "nonce" until
the hash function yields a value, that has the rare property of being below a certain
target threshold. (In other words: The hash "starts with a certain number of zeroes",
if you display it in the fixed-length representation, that is typically used.)

As can be seen, the mining process doesn't compute anything special. It merely
tries to find a number (also referred to as nonce) which - in combination with the payload -
results in a hash with special properties.

The advantage of using such a mechanism consists of the fact, that it is very easy to check a result: Given the payload and a specific nonce, only a single call of the hashing function is needed to verify that the hash has the required properties. Since there is no known way to find these hashes other than brute force, this can be used as a "proof of work" that someone invested a lot of computing power to find the correct nonce for this payload.

This feature is then used in the Bitcoin network to secure various aspects. An attacker
that wants to introduce malicious payload data into the network, will need to do the
required proof of work before it will be accepted. And as long as honest miners have more
computing power, they can always outpace an attacker.

Also see [http://en.wikipedia.org/wiki/Hashcash Hashcash] and [http://en.wikipedia.org/wiki/Proof-of-work_system Proof-of-work system] and [http://en.wikipedia.org/wiki/SHA2 SHA2] and on Wikipedia.

===Why was the "Generate coin" option of the client software removed?===

In the early days of Bitcoin, it was easy for anyone to find new blocks using standard CPUs. As more and more people started mining, the [[difficulty]] of finding new blocks has greatly increased to the point where the average time for a CPU to find a single block can be many years. The only cost-effective method of [[Mining|mining]] is using a high-end graphics card with special software (see also [[Why a GPU mines faster than a CPU]]) and/or joining a [[Bitcoin Pool|mining pool]]. Since solo CPU mining is essentially useless, it was removed from the GUI of the Bitcoin software.

==Security==

===Could miners collude to give themselves money or to fundamentally change the nature of Bitcoin?===

There are two questions in here. Let's look at them separately.

;Could miners gang up and give themselves money?

Mining itself is the process of creating new blocks in the block chain. Each block contains a list of all the transactions that have taken place across the entire Bitcoin network since the last block was created, as well as a hash of the previous block. New blocks are 'mined', or rather, generated, by Bitcoin clients correctly guessing sequences of characters in codes called 'hashes,' which are created using information from previous blocks. Bitcoin users may download specialized 'mining' software, which allows them to dedicate some amount of their processing power – however large or small – to guessing at strings within the hash of the previous block. Whoever makes the right guess first, thus creating a new block, receives a reward in Bitcoins.

The block chain is one of the two structures that makes Bitcoin secure, the other being the public-key encryption system on which Bitcoin trade is based. The block chain assures that not only is every single transaction that ever takes place recorded, but that every single transaction is recorded on the computer of anyone who chooses to store the relevant information. Many, many users have complete records of every transaction in Bitcoins history readily available to them at any point, and anyone who wants in the information can obtain it with ease. These things make Bitcoin very hard to fool.

The Bitcoin network takes considerable processing power to run, and since those with the most processing power can make the most guesses, those who put the most power toward to sustaining the network earn the most currency. Each correct guess yields, at present, twenty-five Bitcoins, and as Bitcoins are presently worth something (although the value still fluctuates) every miner who earns any number of Bitcoins makes money. Some miners pull in Bitcoins on their own; and some also join or form pools wherein all who contribute earn a share of the profits.

Therefore, first answer is a vehement “yes” – not only can miners collude to get more money, Bitcoin is designed to encourage them to do so. Bitcoin pools are communal affairs, and there is nothing dishonest or underhanded about them.

Of course, the real question is:

;Can they do so in ways not sanctioned by Bitcoin developers? Is there any way to rip off the network and make loads of money dishonestly?

Bitcoin isn't infallible. It can be cheated, but doing so is extremely difficult. Bitcoin was designed to evade some of the central problems with modern currencies – namely, that their trustworthiness hinges upon that of people who might not have users' best interests in mind. Every currency in the world (other than Bitcoin) is controlled by large institutions who keep track of what's done with it, and who can manipulate its value. And every other currency has value because people trust the institutions that control them.

Bitcoin doesn't ask that its users trust any institution. Its security is based on the cryptography that is an integral part of its structure, and that is readily available for any and all to see. Instead of one entity keeping track of transactions, the entire network does, so Bitcoins are astoundingly difficult to steal, or double-spend. Bitcoins are created in a regular and predictable fashion, and by many different users, so no one can decide to make a whole lot more and lessen their value. In short, Bitcoin is designed to be inflation-proof, double-spend-proof and completely distributed.

Nonetheless, there are a few ways that one can acquire Bitcoins dishonestly. Firstly, one can steal private keys. Key theft isn't something that Bitcoin security has been designed to prevent: it's up to users to keep theirs safe. But the cryptography is designed so that it is completely impossible to deduce someone's private key from their public one. As long as you keep your private key to yourself, you don't have much to worry about. Furthermore, one could theoretically create a new block chain, but due to the way in which the block chain is constructed, this would be extremely difficult and require massive amounts of processing power. A full explanation of the difficulties involved can be found in the [[block chain]] article.

Bitcoin can be ripped off – but doing so would be extremely hard and require considerable expertise and a staggering amount of processing power. And it's only going to get harder with time. Bitcoin isn't impenetrable, but it's close enough to put any real worries in the peripherals.

;Could miners fundamentally change the nature of Bitcoin?

Once again, almost certainly not.

Bitcoin is a distributed network, so any changes implemented to the system must be accepted by all users. Someone trying to change the way Bitcoins are generated would have to convince every user to download and use their software – so the only changes that would go through are those that would be equally benefit all users.

And thus, it is more or less impossible for anyone to change the function of Bitcoin to their advantage. If users don't like the changes, they won't adopt them, whereas if users do like them, then these will help everyone equally. Of course, one can conceive of a situation where someone manages to get a change pushed through that provides them with an advantage that no one notices, but given that Bitcoin is structurally relatively simple, it is unlikely that any major changes will go through without someone noticing first.

The fact that such changes are so difficult to make testifies to the fully distributed nature of Bitcoin. Any centrally controlled currency can be modified by its central agency without the consent of its adherents. Bitcoin has no central authority, so it changes only at the behest of the whole community. Bitcoins development represents a kind of collective evolution; the first of its kind among currencies.

==Help==
===I'd like to learn more. Where can I get help?===

* Read the [[Introduction|introduction to bitcoin]]
* See the videos, podcasts, and blog posts from the [[Press]]
* Read and post on the [[:Bitcoin:Community_portal#Bitcoin_Community_Forums|forums]]
* Chat on one of the [[:Bitcoin:Community_portal#IRC_Chat|Bitcoin IRC]] channels
* Listen to [http://omegataupodcast.net/2011/03/59-bitcoin-a-digital-decentralized-currency/ this podcast], which goes into the details of how bitcoin works
* Ask questions on the [http://bitcoin.stackexchange.com Bitcoin Stack Exchange]

==See Also==

* [[Man page]]
* [[Introduction]]

[[de:FAQ]]
[[zh-cn:FAQ]]
[[fr:FAQ]]
[[ru:FAQ]]

[[Category:Technical]]
[[Category:Vocabulary]]

Template:MainPage Topics

2013-03-08T20:47:31Z

Atheros: Removed press coverage link because it is quite obsolete. Added link to the page on the History article since it is more relevant there.

{|cellpadding="2" style="background-color: inherit;"
|-
| scope="col" style="width: 200px;" |
* [[Introduction]]
* [http://www.weusecoins.com/getting-started.php Getting started]
* [[Myths]]
* [[Securing your wallet]]
| scope="col" style="width: 200px;" |
* [[PHP developer intro]]
* [[API reference (JSON-RPC)]]
* [[Protocol specification]]
* [[Secure Trading|Best practices for traders]]
* [[Bitcoin Improvement Proposals]]
|}

{|cellpadding="2" style="background-color: inherit;"
|-
! scope="col" style="width: 200px;" |
! scope="col" style="width: 200px;" |
|-
|
* [[Software]]
* [[Mining]]
* [[:Category:Exchanges|Exchanges]]
* [[:Category:Directories|Local Directories]]
* [[:Category:Marketing|Marketing resources]]
* [[People]]
|
* [[:Category:Technical|Technical articles]]
* [[:Category:Clients|Clients]] / [[:Category:Frontends|Frontends]]
* [[:Category:Economics|Economics]]
* [[Trade|Businesses (Trade)]]
* [[:Category:Games|Games]]
* [[Real world shops|Real world merchants map]]
* [[Donation-accepting_organizations_and_projects|Donation-accepting sites]]
* [[Meetups]]
|}

<div style="text-align: right;" class="noprint">[{{fullurl:Template:MainPage_Topics|action=edit}} '''Edit'''] – '''[[Special:Categories|See More]]'''</div>

Category:History

2013-03-08T20:46:33Z

Atheros: /* See Also */

== Important milestones of the Bitcoin project ==
=== 2008 ===
{| style="text-align: left"
|-
! width="8em" | August 18
|| Domain name "bitcoin.org" registered<ref>[https://bitcointalk.org/index.php?topic=103369.msg1135218#msg1135218 According to theymos], Satoshi registered bitcoin.org via https://www.anonymousspeech.com/ which allows to anonymously register domains.</ref>.
|-
! October 31
|| [http://article.gmane.org/gmane.comp.encryption.general/12588/ Bitcoin design paper] published
|-
! November 09
|| Bitcoin project registered at SourceForge.net
|}

=== 2009 ===
{| style="text-align: left"
|-
! width="8em" | January 3
|| [http://www.BlockExplorer.com/b/0 Genesis block] established at 18:15:05 GMT
|-
! January 11
|| Bitcoin v0.1 released and announced on the [http://www.mail-archive.com/cryptography@metzdowd.com/msg10152.html cryptography mailing list]
|-
! January 12
|| First Bitcoin transaction, [http://www.BlockExplorer.com/b/170 in block 170] - from [[Satoshi]] to Hal Finney<ref>[http://bitcointalk.org/index.php?topic=91806.msg1012234#msg1012234 Earliest Block With A Spend]</ref>.
|-
! October 5
|| Exchange rates [http://newlibertystandard.wetpaint.com/page/2009+Exchange+Rate published] by New Liberty Standard. $1 = 1,309.03 BTC (and [[User:theymos|theymos]] thought NLS was overcharging<ref>[http://bitcointalk.org/index.php?topic=104287.msg1143955#msg1143955 Historical Price Data for 2009]</ref>)
|-
! October 9
|| #bitcoin-dev channel registered on freenode IRC.
|-
! December 16
|| Bitcoin v0.2 released
|-
! December 30
|| First difficulty increase at 06:11:04 GMT
|}

=== 2010 ===
{| style="text-align: left"
|-
! width="8em" | February 6
|| [[Bitcoin Market]] established
|-
! May 21
|| laszlo first to buy pizza with Bitcoins agreeing upon paying 10,000 BTC for ~$25 worth of pizza courtesy of jercos<ref>[https://bitcointalk.org/index.php?topic=137.msg1195#msg1195 bitcointalk post] where laszlo confirmed having bought pizza</ref>
|-
! July 7
|| Bitcoin v0.3 released
|-
! July 11
|| Bitcoin v0.3 release mentioned on slashdot<ref>[http://news.slashdot.org/story/10/07/11/1747245/Bitcoin-Releases-Version-03 slashdot] metiones Bitcoin</ref>, bringing a large influx of new bitcoin users.
|-
! July 12
|| Beginning of a 10x increase in exchange value over a 5 day period, from about $0.008/BTC to $0.08/BTC
|-
! July 17
|| [[MtGox]] established
|-
! July 18
|| ArtForz generated his first block after establishing his personal OpenCL GPU hash farm
|-
! August 15
|| Bug in the bitcoin code allows a bad transaction into block 74638. Users quickly adopt fixed code and the "good" block chain overtook the bad one at a block height of 74691, 53 blocks later ([[Incidents#Value_overflow]]).
|-
! September 14
|| jgarzik [https://bitcointalk.org/index.php?topic=133.msg12921#msg12921 offered] 10,000 BTC (valued at ~$600-650) to puddinpop to open source their windows-based CUDA client
|-
! September 14
|| Block [http://blockexplorer.com/b/79764 79,764] is first to be mined using split allocation of the generation reward.
|-
! September 18
|| puddinpop [https://bitcointalk.org/index.php?topic=133.msg13135#msg13135 released] source to their windows-based CUDA client under MIT license
|-
! September 29
|| kermit [https://bitcointalk.org/index.php?topic=1306.0 discovered] a microtransactions exploit which precipitated the Bitcoin v0.3.13 release
|-
! October 01
|| First public OpenCL miner released
|-
! October 04
|| Original Bitcoin History wiki page (this page) established (ooh so meta) on Bitcoin.org's wiki.
|-
! October 07
|| Exchange rate started climbing up from $0.06/BTC after several flat months.
|-
! October 16
|| First recorded escrowed bitcoin trade conducted, between nanotube and Diablo-D3, escrowed by theymos.
|-
! October 17
|| [[Bitcoin_OTC|#bitcoin-otc]] trading channel established on freenode IRC.
|-
! October 28
|| First bitcoin short sale transaction initiated, with a loan of 100 BTC by nanotube to [[User:Kiba|kiba]], facilitated by the [[Bitcoin-otc|#bitcoin-otc]] market.
|-
! November 6
|| The [https://bitcointalk.org/index.php?topic=1672 Bitcoin economy passed US $1 million]. The MtGox price touched USD $0.50/BTC.
|-
! December 7
|| Bitcoind was compiled for the Nokia N900 mobile computer by doublec. The following day, ribuck sent him 0.42 BTC in the first portable-to-portable Bitcoin transaction.
|-
! December 9
|| The generation difficulty passed 10,000.
|-
|
|| First bitcoin call option contract sold, from nanotube to [[User:Sgornick|sgornick]], via the [[Bitcoin-otc|#bitcoin-otc]] market.
|-
! December 16
|| [http://mining.bitcoin.cz/ Bitcoin Pooled Mining], operated by slush, found its first block
|}

=== 2011 ===
{| style="text-align: left"
|-
! width="8em" | January 2
|| [[Tonal Bitcoin]] units standardized.
|-
! January 8
|| [[History of Bitcoin]] page (this page) created after replicating from original Bitcoin History page on Bitcoin.org.
|-
|
|| Bitcoin Pooled Mining reached a total of 10,000 Mhash/s
|-
! January 27
|| Largest numeric value ever traded for bitcoins thus far occurred on this date. Three currency bills from Zimbabwe, known as Zimdollars, were traded on [[Bitcoin-otc|#bitcoin-otc]] at the rate of 4 BTC for each of the one-hundred trillion dollar ($100,000,000,000,000) Zimbabwe notes<ref>Serial numbers for Zimdollars sold: AA1669317, AA1669318 and AA1669319</ref>
|-
! January 28
|| Block 105000 was generated. This means that 5.25 million bitcoins have been generated, which is just over one-quarter of the eventual total of nearly 21 million.
|-
! February 9
|| Bitcoin reached parity with the US dollar, touching $1 per BTC at [[MtGox]].
|-
! February 10
|| Bitcoin.org website struggles to handle [https://bitcointalk.org/index.php?topic=3444.0 traffic] resulting from mentions on Slashdot<ref>[http://news.slashdot.org/story/11/02/10/189246/Online-Only-Currency-BitCoin-Reaches-Dollar-Parity Online-Only Currency BitCoin Reaches Dollar Parity]</ref>, Hacker News and Twitter following the news that parity had been reached.
|-
! February 14
|| A vehicle was, for the first time, offered in exchange for a certain number of bitcoins<ref>[https://bitcointalk.org/index.php?topic=3485.0 Car for Sale - Australia]</ref>.
|-
! March 6
|| Total Bitcoin network computation speed for a short time reached a new high of almost 900Ghash/sec, dropping to 500Ghash/sec soon after. Some speculate that this was due to some supercomputer or bot-net that joined the network ([http://bitcoin.atspace.com/mysteryminer.html mystery miner]).
|-
! March 18
|| BTC/USD exchange rate reaches a 6-week low point at almost $0.70/BTC, after what appeared to be a short burst of, possibly automated, BTC sales at progressively lower prices. BTC price had been declining since the February 9 high.
|-
! March 25
|| Difficulty decreased nearly 10%. A decrease has only occurred once before, and this decrease of nearly 10% was the largest.
|-
! March 27
|| The first market for exchanging bitcoins to and from the British Pound Sterling BTC/GBP, [[Britcoin]], opens.
|-
! March 31
|| The first market for exchanging bitcoins to and from Brazilian Reals, [[Bitcoin Brazil]], opens.
|-
! April 5
|| The first market for exchanging bitcoins to and from the Polish złoty, [[BitMarket.eu]], opens.
|-
! April 12
|| First bitcoin put option contract sold via the [[Bitcoin-otc|#bitcoin-otc]] market.
|-
! April 16
|| TIME does [http://techland.time.com/2011/04/16/online-cash-bitcoin-could-challenge-governments/ an article on Bitcoin].
|-
! April 23
|| BTC/USD exchange rate reaches and passes parity with the Euro (EUR) on [[MtGox]] exchange.
|-
|
|| BTC/USD exchange rate reaches and passes parity with the British Sterling Pound (GBP) on [[MtGox]] exchange.
|-
|
|| Value of the Bitcoin money stock at current exchange rate passes $10 million USD threshold.
|-
! April 27
|| [[VirWoX]] opens first market to trade bitcoins against a virtual currency on BTC/SL (Second Life Lindens) exchange.
|-
! April 30
|| The generation difficulty passed 100,000.
|-
! June 2
|| The exchange rate at [[MtGox]] touched 10 USD per BTC.
|-
! June 3
|| [[Tonal Bitcoin]] reached parity with the US cent, touching 1¢ per TBC at [[Bitcoin Market]].
|-
! June 8
|| The [[MtGox]] exchange rate peaked at 31.91 USD, at a "market capitalization" of about $206 M [http://bitcoin.stackexchange.com/questions/2047/market-capitalization-over-time].
|-
! June 12
|| The [[MtGox]] exchange rate briefly dropped to near 10 USD four days after the peak, in its largest percentage price retreat to date.
|-
! June 13
|| Forum user allinvain claimed to have had [http://forum.bitcoin.org/index.php?topic=16457.0 25,000 BTC stolen] from his Bitcoin wallet (approx. USD equivalent $375,000).
|-
! June 19
|| The MtGox database was compromised and the user table was leaked, containing details of 60,000 usernames, email addresses and password hashes, some of which were based on a highly vulnerable hashing algorithm.
|-
! June 19
|| Someone was able to access an admin account at MtGox and issue sell orders for hundreds of thousands of fake bitcoins, forcing the MtGox price down from $17.51 per bitcoin to $0.01. MtGox announced that these trades would be reversed. Trading was halted at MtGox for 7 days (and also briefly at TradeHill and Britcoin while their security was reviewed).
|-
! June 19
|| Some of the users on the leaked MtGox database had used the same username at MyBitcoin and had their passwords hacked. About 600 of them had their balance [http://forum.bitcoin.org/index.php?topic=22221.msg279396#msg279396 stolen from their MyBitcoin accounts]. One user lost over 2000 BTC.
|-
! June 20
|| The EFF announced that it was no longer accepting Bitcoin donations due to legal uncertainties.
|-
! June 24
|| The generation difficulty passed 1,000,000 with Block [http://blockexplorer.com/b/133056 133056].
|-
! July 19
|| "Let it go on record that at 4:05pm CET [19 July 2011], my manager Tadek was the first person in the world to receive [testnet] Bitcoins via NFC ;)" - Mike Hearn
|-
! July 22
|| [[BitCoins Mobile]], the first Bitcoin application for iPad was released by [http://www.intervex.net Intervex Digital].
|-
! July 30
|| [http://pastebin.com/raw.php?i=BUB3dygQ Tribute to Len Sassaman] included in the blockchain<ref>[http://bitcointalk.org/index.php?topic=33618.msg420597#msg420597 A Tribute to Len "rabbi" Sassama]</ref>.
|-
! August 20
|| First Bitcoin Conference and World Expo held, in NYC.<ref>[http://bitcoinme.com/index.php/conference/ New York Conference 2011]</ref>
|-
! August 23
|| [[P2Pool]], the first P2P decentralized pool, mines its first Bitcoin mainnet block (Block [http://blockexplorer.com/b/142312 142,312]).
|-
! August 30
|| Difficulty adjustment at block [http://blockexplorer.com/b/143136 143,136] marks the first back-to-back drop.
|-
! November 15
|| First CVE (CVE-2011-4447) assigned to a Bitcoin client exploit.
|-
! November 25
|| First European Bitcoin Conference in Prague, Czech Rep.<ref>[http://bitgroups.org/ Prague Conference 2011]</ref>
|-
! December 12
|| Largest amount of fees, to-date, in a single transaction, and most fees in a single block. A [http://blockexplorer.com/tx/1d7749c65c90c32f5e2c036217a2574f3f4403da39174626b246eefa620b58d9 transaction] paid 171 BTC in fees in [http://blockexplorer.com/b/157235 block 157235]<ref>[http://bitcointalk.org/index.php?topic=88423.msg973509#msg973509 Largest fee ever?]</ref>.
|}

=== 2012 ===
{| style="text-align: left"
|-
! width="8em" | March 1
|| Largest theft of bitcoins to-date occurred (near 50K BTC) after security breach at web host Linode.
|-
! width="8em" | April 1
|| Pay-to-script-hash ([[P2SH]]) as defined through [[BIP 0016]] goes live.
|-
! May 08
|| A single service, [[SatoshiDICE]] becomes responsible for over half the transaction volume on the Bitcoin blockchain.
|-
! June 3
|| Largest block (most transactions), to-date (June 3), is [http://BlockExplorer.com/b/181919 block 181919] with 1322 transactions<ref>[http://bitcointalk.org/index.php?topic=85353.msg939859#msg939859 Largest block to date]</ref>.
|-
! July 22
|| One millionth topic reply was posted on the unofficial [[Bitcoin Forum]] <ref>[https://bitcointalk.org/index.php?topic=94608.0 Topic about one millionth forum post]</ref>.
|-
! September 15-16
|| Bitcoin Conference in London <ref>[http://bitcoin2012.com/ London Conference 2012]</ref>.
|-
! September 27
|| Formation of the [[Bitcoin Foundation]].
|-
! November 28
|| Halving day. [http://blockexplorer.com/b/210000 Block 210,000] is the first with a block reward subsidy of only 25 BTC.
|-
! December 6
|| First Bitcoin exchange [https://bitcointalk.org/index.php?topic=129461.0 licensed "as a bank" in europe] (actually a PSP which is like a bank, without debt-money issuing).
|}

=== 2013 ===
{| style="text-align: left"
|-
! width="8em" | February 19
|| Bitcoin Client v0.8 released featuring improved download speed and [https://en.wikipedia.org/wiki/Bloom_filter Bloom Filtering]
|-
! February 28
|| The [[MtGox]] exchange rate broke the June 8 2011 peak of 31.91 USD. The first all time high since 601 days
|-
|}

==See Also==

* [[Bitcoin Firsts]]
* [[Press]]

==References==
<references />

Press

2013-03-08T20:46:11Z

Atheros:

This article lists Bitcoin-related press from the project's creation through October 2011. Since that time, due to the increased frequency of published articles, a [http://bitcointalk.org/index.php?board=77.0 Press forum board] was created on the BitcoinTalk Forum to allow the wider Bitcoin community to share articles as they are discovered.

__TOC__

==Press and notable mentions==
==Articles / Blog Posts==
=== 2011 ===
==== October====
{{Press
| source = techradar.com
| country = UK
| language = en
| title = The death of money Electronic payments are everywhere. Is it time for cash to take a hike?
| date = 2011-10-15
| link = http://www.techradar.com/news/phone-and-communications/mobile-phones/the-death-of-money-1033374
| bias = balanced
| quote1 = By 2015, cash could be looking like an endangered species.
| quote2 = So is Bitcoin the future of money, or is it only of interest to currency fans, cyber-utopians and speculators?
| screenshot = ScreenshotTechRadar201110.png
}}
{{Press
| source = The Guardian
| country = UK
| language = en
| title = Bitcoin value crashes below cost of production as broader use stutters
| date = 2011-10-18
| link = http://www.guardian.co.uk/technology/2011/oct/18/bitcoin-value-crash-cryptocurrency
| bias = negative and stupidly wrong
| quote1 = the appreciation in value was a speculative bubble, caused by people hoarding the currency, rather than the start of a new (or parallel) economy.
| quote2 = With the value of Bitcoins dropping so low, and the computing power required to produce them growing steadily, it is becoming uneconomic to generate more except through the use of hacked computers in "botnets".
| screenshot = Screenshot_theGuardian201110.png
}}

==== July ====

{{Press
| source = PacoAhlgren.com
| country = US
| language = en
| title = Bitcoin Cannot Fail
| date = 2011-07-25
| link = http://www.pacoahlgren.com/bitcoin-cannot-fail/
| bias = angrily positive
| quote1 = They can’t make the rules. And that scares the hell out of them.
| quote2 = This may be the purest form of democracy the world has ever known, and I — for one — am thrilled to be here to watch it unfold.
| screenshot = ArticlePacoAhlgren20110725.png
}}

{{Press
| source = canada.com
| country = Canada
| language = en
| title = Bitcoins create truly democratic policy, followers say
| date = 2011-07-22
| link = http://www.canada.com/Bitcoins+create+truly+democratic+policy+followers/5144669/story.html
| bias = very positive
| quote1 = Money may be the next frontier of the Internet revolution thanks to Bitcoin, a burgeoning new digital currency.
| quote2 = ``If we remember, 15 years ago if you were doing anything on the Internet you were going to make millions,'' said Kenna. ``I think it could be the same with bitcoin.''
| screenshot = ArticleCanadaCom.png
}}

{{Press
| source = npr.org
| country = United States
| language = en
| title = The Tuesday Podcast: Bitcoin
| date = 2011-07-12
| link = http://www.npr.org/blogs/money/2011/07/13/137795648/the-tuesday-podcast-bitcoin
| bias = neutral to slightly negative
| quote1 = I have to say this part of the whole Bitcoin thing for us did seem really easy. Easier than using a credit card or wiring a friend some money.
| screenshot = ArticleNPR201107.png
}}

==== June ====
{{Press
| source = The Economist
| country = GB
| language = en
| title = Bits and bob
| date = 2011-06-13
| link = http://www.economist.com/blogs/babbage/2011/06/virtual-currency
| bias = neutral
| quote1 = Now, Friedman's dream has finally been realised—albeit not by a real-world central bank.
| quote2 = Most people would rather devolve this sort of responsibility to the authorities. Until this mindset changes, Bitcoin will be no rival to real-world dosh.
| screenshot = ArticleEconomistBitsAndBob.png
}}

{{Press
| source = Telepolis
| country = DE
| language = de
| title = Wenig Unterschied zu Aktien
| date = 2011-06-10
| link = http://www.heise.de/tp/artikel/34/34919/1.html
| bias = skeptical
| quote1 = Stoppt die amerikanischen Drogenpolizei DEA den Höhenflug der Bitcoin-Währung?
| quote2 = Silk Road dürfte unter anderem deshalb schwer zu schließen sein, weil Betreiber ebenso wie Benutzer durch TOR weitgehend anonym sind.
| screenshot = ArticleTelepolis20110610.png
}}

{{Press
| source = Smart Money
| country = USA
| language = en
| title = The Bitcoin Triples Again
| date = 2011-06-10
| link = http://www.smartmoney.com/invest/stocks/the-bitcoin-triples-again-1307638613180
| bias = critical
| quote1 = To recap, it's is a purely online currency with no intrinsic value; its worth is based solely on the willingness of holders and merchants to accept it in trade.
| quote2 = Readers tempted to bet on the Bitcoin should resist, not least because it's unclear whether it will have any enduring worth.
| screenshot = ArticleSmartMoneyBitcoinTriples.png
}}

==== May ====
* [http://www.technologyreview.com/computing/37619 What Bitcoin Is, and Why It Matters] 2011-05-24 Technology Review by MIT
* [http://www.thedaily.com/page/2011/05/23/052311-apps-technews-bitcoins-1-2/ Bit Players, An open source digital currency seeks to gain wider acceptance] 2011-05-23 iPad news app The Daily
* [http://www.slate.com/id/2294980 My Money Is Cooler Than Yours] 2011-05-18 Slate
* [http://launch.is/blog/l019-bitcoin-p2p-currency-the-most-dangerous-project-weve-ev.html L019: Bitcoin P2P Currency: The Most Dangerous Project We've Ever Seen] 2011-05-15 Launch
* [http://gizmodo.com/5803518/what-is-bitcoin What Is BitCoin?] 2011-05-19 Gizmodo.com
* [http://arstechnica.com/tech-policy/news/2011/06/bitcoin-inside-the-encrypted-peer-to-peer-currency.ars Bitcoin: inside the encrypted, peer-to-peer digital currency] 2011-06-08 Ars Technica

==== April ====
* [http://www.forbes.com/forbes/2011/0509/technology-psilocybin-bitcoins-gavin-andresen-crypto-currency.html Crypto Currency] 2011-04-20 Forbes Magazine
* [http://techland.time.com/2011/04/16/online-cash-bitcoin-could-challenge-governments Online Cash Bitcoin Could Challenge Governments, Banks] 2011-04-16 TIME TechLand

==== March ====
* [http://ironwolf.dangerousgames.com/blog/archives/1063 Bitcoin: It's Not Too Late To Send Me Money] 2011-03-27 Ironwolf Blog
* [http://www.cio.com.au/article/380394/open_source_identity_bitcoin_technical_lead_gavin_andresen Open source identity: Bitcoin technical lead Gavin Andresen] 2011-03-21 CIO Australia
* [http://civicactions.com/blog/2011/mar/14/what_the_frack_is_bitcoin_and_can_i_use_it_with_drupal What the Frack is Bitcoin and Can I Use it with Drupal?] 2011-03-14 CivicActions
* [http://www.howtogeek.com/howto/44718/htg-explains-what-is-bitcoin HTG Explains: What Is Bitcoin, the Virtual Digital Currency?] 2011-03-01 HowToGeek.com

==== Feb ====
* [http://news.slashdot.org/story/11/02/10/189246/Online-Only-Currency-BitCoin-Reaches-Dollar-Parity Online-Only Currency BitCoin Reaches Dollar Parity] 2011-02-10 news.Slashdot.org

==== Jan ====
{{Press
| source = Electronic Frontier Foundation (EFF)
| country = USA
| language = en
| title = Bitcoin - a Step Toward Censorship-Resistant Digital Currency
| date = 2011-01-20
| link = http://www.eff.org/deeplinks/2011/01/bitcoin-step-toward-censorship-resistant
| bias = balanced to positive
| quote1 = To understand digital currency, one must first note that money in the digital age has moved from a largely anonymous system to one increasingly laden with tracking, control and regulatory overhead.
| quote2 = It's too early to say whether Bitcoin will be a success. Any new currency system faces an uphill battle, both technically and legally.
| screenshot = ArticleEFF201101.png
}}

=== 2010 ===
* [http://www.readwriteweb.com/hack/2010/12/interview-bitcoin.php Interview: How Bitcoin Created a Decentralized Crypto-Currency] 2010-12-29 ReadWriteWeb
* [http://www.pcworld.com/businesscenter/article/213230/could_the_wikileaks_scandal_lead_to_new_virtual_currency.html Could the Wikileaks Scandal Lead to New Virtual Currency?] 2010-12-10 PC World
* [http://www.irishtimes.com/newspaper/finance/2010/1126/1224284180416.html Imagine your computer as a wallet full of Bitcoins] 2010-11-26 Irish Times

{{Press
| source = LWN
| country = USA
| language = en
| title = Bitcoin: Virtual money created by CPU cycles
| date = 2010-11-10
| link = http://lwn.net/Articles/414452/
| bias = positive
| quote1 = The bigger open questions about Bitcoin are about its viability as a currency system.
| quote2 = Bitcoin is different from electronic payment systems like Paypal that are really just computerized interfaces to traditional banks.
| screenshot = ArticleLWN2010.png
}}

{{Press
| source = Bitcoin Blogger
| country = ?
| language = en
| title = Bitcoin Electronic Currency: The Future of Money
| date = 2010-09-30
| link = http://www.bitcoinblogger.com/2010/09/bitcoin-electronic-currency-future-of.html
| bias = positive
| quote1 =
| quote2 =
| screenshot = ArticleBitcoinBlogger2010.png
}}

{{Press
| source = /.
| country = USA
| language = en
| title = Bitcoin Releases Version 0.3
| date = 2010-07-11
| link = http://news.slashdot.org/story/10/07/11/1747245/Bitcoin-Releases-Version-03
| bias = neutral
| quote1 =
| quote2 =
| screenshot = ArticleSlashDot2010.png
}}

===Podcasts / Video===
* [http://www.youtube.com/watch?v=1ZAFGRrp_kc Free Talk Live - interview with Roger Ver] 2011-11-19 An hour-long interview with Roger Ver of Memorydealers.com
* [http://surprisinglyfree.com/2012/01/31/reuben-grinberg Reuben Grinberg on the legality of Bitcoin] 2011-01-31 ([http://surprisinglyfree.com/wp-content/uploads/SFC-101-122701.mp3 mp3])
* [http://www.npr.org/blogs/money/2011/07/12/137795648 NPR Planet Money - The Tuesday Podcast: Bitcoin] 2011-07-12 ([http://pd.npr.org/anon.npr-mp3/npr/specials/2011/07/20110712_specials_pmoney.mp3?dl=1 mp3])
* [http://sixgun.org/linuxoutlaws-215 Linux Outlaws 215 - Bitcoins] 2011-06-30 ([http://traffic.libsyn.com/linuxoutlaws/linuxoutlaws215.mp3 mp3], [http://linuxoutlaws.com/podcast/ogg/215 ogg])
* [http://www.youtube.com/watch?v=jYiWHNkZIes CBS / What’s Trending - Bitcoin: The Future Of Money] 2011-06-08 Shira Lazar interviews Bitcoin [[Developers|developer]] Jeff Garzik.
* [http://www.youtube.com/watch?v=gcn8cNCk9hM The World's First Bitcoin Road Trip] 2011-05-30 An interview with The Real Plato on the Corbett Report.
* [http://www.npr.org/2011/05/24/136620231/what-are-bitcoins What Are Bitcoins?] 2011-05-24 NPR All Things Considered ([http://pd.npr.org/anon.npr-mp3/npr/atc/2011/05/20110524_atc_08.mp3?dl=1 mp3])
* [http://youtube.com/watch?v=TwNfBgwbqng TWIST #140] 2011-05-10 This Week In Startups interviews Gavin Andresen and Britcoin's Amir Taaki
* [http://agoristradio.com/?p=112 Cypherpunkd Episode 005: "Bitcoin Mania" Part 1 - mids] 2011-04-06 Podcast interview of mids, from AgoristRadio.com ([http://library.agoristradio.com/library/cypherpunkd/cypherpunkd-EP005.mp3 mp3])
* [http://vimeo.com/22072121 Bitcoin at EPCA] 2011-04-04 Video of Genjix's presentation on Bitcoin at EPCA conference. ([http://www.dyndy.net/2011/04/bitcoin-presented-to-the-old-world followup])
* [http://www.econtalk.org/archives/2011/04/andresen_on_bit.html Andresen on BitCoin and Virtual Currency] 2011-04-04 EconTalk's Russell Roberts interview Bitcoin lead Gavin Andresen ([http://files.libertyfund.org/econtalk/y2011/Andresenbitcoin.mp3 mp3], [http://www.econtalk.org/archives/2011/04/andresen_on_bit.html#highlights transcript])
* [http://www.youtube.com/watch?v=Um63OQz3bjo What is Bitcoin?] video introduction ([http://c2995102.r2.cf0.rackcdn.com/What_is_Bitcoin_hd.mp4 mp4])
* [http://omegataupodcast.net/2011/03/59-bitcoin-a-digital-decentralized-currency Bitcoin – a Digital, Decentralized Currency] 2011-03-18 omega tau interviews Bitcoin technical lead [[User:gavinandresen|Gavin Andresen]] ([http://traffic.libsyn.com/omegataupodcast/omegatau-59-bitcoin.mp3 podcast])
* [http://www.cbc.ca/spark/2011/02/spark-139-february-27-march-2-2011 Spark 139] 2011-02-27 CBC Radio covers Bitcoin. A nice non-technical overview ([http://podcast.cbc.ca/mp3/spark_20110227_45926.mp3 podcast])
* [http://www.youtube.com/watch?v=RCzsCmhkjMM Security Now 288: Q&A] 2011-02-16 Bitcoin coverage is from 0:44:00 to about 1:13 of the podcast ([http://www.podtrac.com/pts/redirect.mp3/aolradio.podcast.aol.com/sn/sn0288.mp3 podcast]),([http://dts.podtrac.com/redirect.mp4/twit.cachefly.net/video/sn/sn0288/sn0288_h264b_864x480_500.mp4 video])
* [http://blip.tv/file/4771178 Ignite Amherst] 2011-02-15 Presentation by Bitcoin Principal [[User:Gavinandresen|Gavin Andresen]] ([http://www.skypaint.com/bitcoin/GavinIgniteTalk.pdf Slides])
* [http://ignite-dc.blip.tv/file/4801077 Ignite D.C. 6] 2011-02-03 Presentation by [[User:Dduane|Darrell Duane]] ([http://bitcoinbasics.com/ignitedc Slides]) About Bitcoin and Potomac local currency
* [http://www.youtube.com/watch?v=XQPSwA2Itbs Security Now 287: BitCoin CryptoCurrency] 2011-02-09 Bitcoin coverage is from 0:41:25 to the end of the netcast ([http://dts.podtrac.com/redirect.mp4/twit.cachefly.net/video/sn/sn0288/sn0288_h264b_864x480_500.mp4 video]), ([http://www.podtrac.com/pts/redirect.mp3/aolradio.podcast.aol.com/sn/sn0287.mp3 podcast])

===Presentations===
* [http://www.slideshare.net/ashmoran/the-barcampers-guide-to-bitcoin-8682810 The BarCamper's Guide to Bitcoin] 2011-07-25 by Ash Moran
* [http://s3.amazonaws.com/gavinandresen-bitcoin/GavinAndresenCIATalk.pdf Bitcoin - The World's 1st P2P Digital Currency] 2011-06-?? Gavin Andresen Presentation given at In-Q-Tel investment conference
* [http://btcbids.com/bitcoin.pdf Bitcoin - P2P Virtual Currency] 2011-06-05 Jake Hansen Presentation submission for Defcon 19<ref>[https://forum.bitcoin.org/index.php?topic=12416.0 Forum I Need help]</ref>
* [http://www.slideshare.net/jonmatonis/monetising-game-play-on-social-network-sites Monetising Game Play on Social Network Sites] 2011-03-31 Jon Matonis at KPMG eGaming Summit
* [http://prezi.com/tbpky5fm7qbl/bitcoin-new-p2p-currency Bitcoin - new P2P currency] 2011-02-19 Juraj Bednar

==See Also==

* [http://bitcointalk.org/index.php?board=77.0 Bitcoin Press] forum board
* [[:Category:Blogs|Blogs]]
* [[Bitcoin News]] daily posts
* [[Research]]

==References==
<references />

[[Category:Marketing]]
[[Category:Introduction]]
[[de:Presse]]

Category:Mining

2013-03-08T20:29:59Z

Atheros: /* Guides */ Obsolete.

For the mining article, see [[Mining]].

==Guides==

* [https://www.coindl.com/page/item/201 Introduction to Bitcoin Mining eBook]
* [http://bitcointalk.org/?topic=7514.0 Ubuntu Natty Narwhal 11.04 Mining Guide / HOWTO]
* [http://bitcointalk.org/index.php?topic=17805.0 MineCo.in pool: Beginners guide to pooled bitcoin mining]
* [[CM1Quickstart| CM1 QuickStart Guide]]

[[zh-cn:Category:开采]]
[[de:Kategorie:Mining]]

Category:Mining

2013-03-08T20:26:33Z

Atheros: /* Guides */ Guide is now obsolete. Please re-add when updated.

For the mining article, see [[Mining]].

==Guides==

* [https://www.coindl.com/page/item/201 Introduction to Bitcoin Mining eBook]
* [http://ewoah.com/technology/a-very-good-guide-to-building-a-bitcoin-mining-rig-cluster-guide eWoah: How to build a Bitcoin Mining Rig Cluster]
* [http://bitcointalk.org/?topic=7514.0 Ubuntu Natty Narwhal 11.04 Mining Guide / HOWTO]
* [http://bitcointalk.org/index.php?topic=17805.0 MineCo.in pool: Beginners guide to pooled bitcoin mining]
* [http://bitclockers.com/forums/index.php?topic=3.0 BitClockers pool: Getting started mining]
* [http://foreverrising.wordpress.com/ Foreverrising: Mining Guides and Overclocking w/ examples]
* [http://btcbase.com/guides/ BTCBase - German Guides: GPU-Mining, Mining-Software, Overclocking w/ examples]
* [[CM1Quickstart| CM1 QuickStart Guide]]

[[zh-cn:Category:开采]]
[[de:Kategorie:Mining]]

Bitcoin Rigs

2013-03-08T20:23:40Z

Atheros: Replaced content with "This page needs to be deleted."

This page needs to be deleted.

BlightyCoin

2013-03-08T20:23:26Z

Atheros: Replaced content with "This page needs to be deleted."

This page needs to be deleted.

Template:MainPage Topics

2013-03-08T20:18:28Z

Atheros: We have an article just for this purpose. It is perfect for beginners.

{|cellpadding="2" style="background-color: inherit;"
|-
| scope="col" style="width: 200px;" |
* [[Introduction]]
* [http://www.weusecoins.com/getting-started.php Getting started]
* [[Myths]]
* [[Securing your wallet]]
| scope="col" style="width: 200px;" |
* [[PHP developer intro]]
* [[API reference (JSON-RPC)]]
* [[Protocol specification]]
* [[Secure Trading|Best practices for traders]]
* [[Bitcoin Improvement Proposals]]
|}

{|cellpadding="2" style="background-color: inherit;"
|-
! scope="col" style="width: 200px;" |
! scope="col" style="width: 200px;" |
|-
|
* [[Software]]
* [[Mining]]
* [[:Category:Exchanges|Exchanges]]
* [[:Category:Directories|Local Directories]]
* [[Press|Press coverage]]
* [[:Category:Marketing|Marketing resources]]
* [[People]]
|
* [[:Category:Technical|Technical articles]]
* [[:Category:Clients|Clients]] / [[:Category:Frontends|Frontends]]
* [[:Category:Economics|Economics]]
* [[Trade|Businesses (Trade)]]
* [[:Category:Games|Games]]
* [[Real world shops|Real world merchants map]]
* [[Donation-accepting_organizations_and_projects|Donation-accepting sites]]
* [[Meetups]]
|}

<div style="text-align: right;" class="noprint">[{{fullurl:Template:MainPage_Topics|action=edit}} '''Edit'''] – '''[[Special:Categories|See More]]'''</div>

Help:Introduction

2013-03-08T20:16:36Z

Atheros: /* Capitalization / Nomenclature */ Capitalization

The purpose of this page is to provide a general overview of the Bitcoin system and economy.

==Basic Concepts==

===Currency===

Alice wants to buy the [http://www.grasshillalpacas.com/alpacaproductsforbitcoinoffer.html Alpaca socks] which Bob has for sale. In return, she must provide something of equal value to Bob. The most efficient way to do this is by using a medium of exchange that Bob accepts which would be classified as currency. Currency makes trade easier by eliminating the need for [http://en.wikipedia.org/wiki/Coincidence_of_wants coincidence of wants] required in other systems of trade such as barter. Currency adoption and acceptance can be global, national, or in some cases local or community-based.

===Banks===

Alice need not provide currency to Bob in-person. She may instead transfer this value by first entrusting her currency to a bank who promises to store and protect Alice's currency notes. The bank gives Alice a written promise (called a "bank statement") that entitles her to withdraw the same number of currency bills that she deposited. Since the money is still Alice's, she is entitled to do with it whatever she pleases, and the bank (like most banks), for a small fee, will do Alice the service of passing on the currency bills to Bob on her behalf. This is done by Alice's bank by giving the dollar bills to Bob's bank and informing them that the money is for Bob, who will then see the amount the next time he checks his balance or receives his bank statement.

Since banks have many customers, and bank employees require money for doing the job of talking to people and signing documents, banks in recent times have been using machines such as ATMs and web servers that do the job of interacting with customers instead of paid bank employees. The task of these machines is to learn what each customer wants to do with their money and, to the extent that it is possible, act on what the customer wants (for example, ATMs can hand out cash). Customers can always know how much money they have in their accounts, and they are confident that the numbers they see in their bank statements and on their computer screens accurately reflect the number of dollars that they can get from the bank on demand. They can be so sure of this that they can accept those numbers in the same way they accept paper banknotes (this is similar to the way people started accepting paper dollars when they had been accepting gold or silver).

Such a system has several disadvantages:
* It is costly. [https://en.wikipedia.org/wiki/Electronic_funds_transfer EFTs] in Europe can cost 25 euros. Credit transactions can cost several percent of the transaction.
* It is slow. Checking and low cost wire services take days to complete.
* In most cases, it cannot be anonymous.
* Accounts can be frozen.
* Banks and other payment processors like PayPal, Visa, and Mastercard may refuse to process payments for legal entities.

Bitcoin is a system of owning and voluntarily transferring amounts of so-called ''bitcoins'', in a manner similar to an on-line banking, but pseudonymously and without reliance on a central authority to maintain account balances. If bitcoins are valuable, it is because they are useful and limited in supply.

==Bitcoin Basics==

===Creation of coins===
The creation of coins must be limited for the currency to have any value.

New coins are slowly [[Mining|mined]] into existence by following a mutually agreed-upon set of rules. A user [[Mining|mining]] bitcoins is running a software program that searches tirelessly for a solution to a very difficult math problem whose difficulty is precisely known. The difficulty is automatically adjusted regularly so that the number of solutions found globally, by everyone, is constant: an average of 6 per hour. When a solution is found, the user may tell everyone of the existence of this newly found solution, along with other information, packaged together in what is called a "[[Block|block]]".

Blocks contain 50 bitcoins at present. This amount, known as the block reward, is an incentive for people to perform the computation work required for generating blocks. Roughly every 4 years, the number of bitcoins that can be "mined" in a block reduces by 50%. Any block that is created by a malicious user that does not follow this rule (or any other rules) will be rejected by everyone else. In the end, no more than 21 million bitcoins will ever exist.

Because the block reward will decrease over the long term, miners will some day instead pay for their hardware and electricity costs by collecting [[Transaction_fee|transaction fees]]. The sender of money may voluntarily pay a small transaction fee which will be kept by whoever finds the next block. Paying this fee will encourage miners to include the transaction in a block more quickly.

===Sending payments===
To guarantee that a third-party, let's call her Eve, cannot spend other people's bitcoins by creating transactions in their names, Bitcoin uses [[Wikipedia:Public-key_cryptography|public key cryptography]] to make and verify digital signatures. In this system, each person, such as Alice or Bob, has one or more addresses each with an associated pair of public and private keys that they may hold in a [[Wallet|wallet]]. Only the user with the private key can sign a transaction to give some of their bitcoins to somebody else, but anyone can validate the signature using that user’s public key.

Suppose Alice wants to send a bitcoin to Bob.
* Bob sends his address (from which the public key can be derived) to Alice.
* Alice adds Bob’s public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Alice signs the transaction with her private key.
* Alice broadcasts the transaction on the Bitcoin network for all to see.

(Only the first two steps require human action. The rest is done by the Bitcoin client software.)

Looking at this transaction from the outside, anyone who knows that these addresses belong to Alice and Bob can see that Alice has agreed to transfer the amount to Bob, because nobody else has Alice's private key. Alice would be foolish to give her private key to other people, as this would allow them to sign transactions in her name, removing funds from her control.

Later on, when Bob wishes to transfer the same bitcoins to Charley, he will do the same thing:
* Charlie sends Bob his address.
* Bob adds Charlie's public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Bob signs the transaction with his private key.
* Bob broadcasts the transaction on the Bitcoin network for all to see.

Only Bob can do this because only he has the private key that can create a valid signature for the transaction.

Eve cannot change whose coins these are by replacing Bob’s public key with her public key, because Alice signed the transfer to Bob using her own private key, which is kept secret from Eve, and instructing that the coins which were hers now belong to Bob. So if Charlie accepts that the original coin was in the hands of Alice, he will also accept the fact that this coin was later passed to Bob, and now Bob is passing this same coin to him.

===Preventing [[double-spending]]===
The process described above does not prevent Alice from using the same bitcoins in more than one transaction. The following process does; this is the primary innovation behind Bitcoin.

* Details about the [[Transactions|transaction]] are [[Network|sent and forwarded]] to all or as many other computers as possible.
* A constantly growing chain of [[Blocks|blocks]] that contains a record of all transactions is collectively maintained by all computers (each has a full copy).
* To be accepted in the chain, transaction blocks must be valid and must include [[proof of work]] (one block generated by the network every 10 minutes).
* Blocks are chained in a way so that, if any one is modified, all following blocks will have to be recomputed.
* When multiple valid continuations to this chain appear, only the longest such branch is accepted and it is then extended further.

When Bob sees that his transaction has been included in a block, which has been made part of the single longest and fastest-growing block chain (extended with significant computational effort), he can be confident that the transaction by Alice has been accepted by the computers in the network and is permanently recorded, preventing Alice from creating a second transaction with the same coin. In order for Alice to thwart this system and double-spend her coins, she would need to muster more computing power than all other Bitcoin users combined.

===Anonymity===
When it comes to the Bitcoin network itself, there are no "accounts" to set up, and no e-mail addresses, user-names or passwords are required to hold or spend bitcoins. Each balance is simply associated with an address and its public-private key pair. The money "belongs" to anyone who has the private key and can sign transactions with it. Moreover, those keys do not have to be registered anywhere in advance, as they are only used when required for a transaction. Transacting parties do not need to know each other's identity in the same way that a store owner does not know a cash-paying customer's name.

A [[Address|Bitcoin address]] mathematically corresponds to a public key and looks like this:

:1PC9aZC4hNX2rmmrt7uHTfYAS3hRbph4UN

Each person can have many such addresses, each with its own balance, which makes it very difficult to know which person owns what amount. In order to protect his [[Anonymity|privacy]], Bob can generate a new public-private key pair for each individual receiving transaction and the Bitcoin software encourages this behavior by default. Continuing the example from above, when Charlie receives the bitcoins from Bob, Charlie will not be able to identify who owned the bitcoins before Bob.

===Capitalization / Nomenclature===
Since Bitcoin is both a currency and a protocol, capitalization can be confusing. Accepted practice is to use ''Bitcoin'' (singular with an upper case letter B) to label the protocol, software, and community, and ''bitcoins'' (with a lower case b) to label units of the currency.

==Where to see and explore==
You can directly explore the system in action by visiting [http://blockchain.info/ Blockchain.info] or [http://blockexplorer.com/ Bitcoin Block Explorer].
The site shows you the latest blocks in the block chain. The [[Block_chain|block chain]] contains the agreed history of all transactions that took place in the system.
Note how many blocks were generated in the last hour, which on average will be 6. Also notice the number of transactions and the total amount transferred in the last hour (last time I checked it was about 64 and 15K).
This should give you an indication of how active the system is.

Next, navigate to one of these blocks.
The block's [[hash]] begins with a run of zeros. This is what made creating the block so difficult; a hash that begins with many zeros is much more difficult to find than a hash with few or no zeros. The computer that generated this block had to try many ''Nonce'' values (also listed on the block's page) until it found one that generated this run of zeros.
Next, see the line titled ''Previous block''. Each block contains the hash of the block that came before it. This is what forms the chain of blocks.
Now take a look at all the transactions the block contains. The first transaction is the income earned by the computer that generated this block. It includes a fixed amount of coins created out of "thin air" and possibly a fee collected from other transactions in the same block.

Drill down into any of the transactions and you will see how it is made up of one or more amounts coming in and out.
Having more than one incoming and outgoing amount in a transaction enables the system to join and break amounts in any possible way, allowing for any fractional amount needed. Each incoming amount is a past transaction (which you can also view) from someone's address, and each outgoing amount is addressed to someone and will be part of a future transaction (which you can also navigate down into if it has already taken place.)

Finally you can follow any of the [[Address|addresses]] links and see what public information is available for them.

To get an impression of the amount of activity on the Bitcoin network, you might like to visit the monitoring websites [[Bitcoin Monitor]] and [[Bitcoin Watch]]. The first shows a real-time visualization of events on the Bitcoin network, and the second lists general statistics on the amount and size of recent transactions.

===How many people use Bitcoin?===

This is quite a difficult question to answer accurately. One approach is to count how many bitcoin clients connected to the network in the last 24 hours. We can do this because some clients transmit their addresses to the other members of the network periodically. In September 2011 this method suggested that there were about {{formatnum:60000}} users.

==See Also==

* [http://www.youtube.com/watch?v=Um63OQz3bjo What is Bitcoin?] video introduction
* Installing Bitcoin [[getting started]]
* [[Using Bitcoin]]
* A gentle introduction to Bitcoin - [[BitcoinMe]]
* [http://coinlab.com/2011/12/bitcoin-primer Bitcoin Primer] from CoinLab
* Another introduction, ''The Rebooting Of Money'' podcast is found at [[Bitcoin Money]]
* A beginner's step-by-step guide to using Bitcoin, use of alternative wallets, and generally keeping your money and computer secure - [http://BitcoinIntro.com BitcoinIntro.com]
* [http://howtobitcoin.info howtobitcoin.info] Directory of bitcoin links for beginners
* Amazon Kindle Book [http://www.amazon.com/Bitcoin-Step-by-ebook/dp/B00A1CUQQU Bitcoin Step by Step] $3.99 (USD). The author walks you step by step through getting started.

[[zh-cn:简介]]

[[de:Einführung]]

Help:Introduction

2013-03-08T20:05:41Z

Atheros: Ambiguous.

The purpose of this page is to provide a general overview of the Bitcoin system and economy.

==Basic Concepts==

===Currency===

Alice wants to buy the [http://www.grasshillalpacas.com/alpacaproductsforbitcoinoffer.html Alpaca socks] which Bob has for sale. In return, she must provide something of equal value to Bob. The most efficient way to do this is by using a medium of exchange that Bob accepts which would be classified as currency. Currency makes trade easier by eliminating the need for [http://en.wikipedia.org/wiki/Coincidence_of_wants coincidence of wants] required in other systems of trade such as barter. Currency adoption and acceptance can be global, national, or in some cases local or community-based.

===Banks===

Alice need not provide currency to Bob in-person. She may instead transfer this value by first entrusting her currency to a bank who promises to store and protect Alice's currency notes. The bank gives Alice a written promise (called a "bank statement") that entitles her to withdraw the same number of currency bills that she deposited. Since the money is still Alice's, she is entitled to do with it whatever she pleases, and the bank (like most banks), for a small fee, will do Alice the service of passing on the currency bills to Bob on her behalf. This is done by Alice's bank by giving the dollar bills to Bob's bank and informing them that the money is for Bob, who will then see the amount the next time he checks his balance or receives his bank statement.

Since banks have many customers, and bank employees require money for doing the job of talking to people and signing documents, banks in recent times have been using machines such as ATMs and web servers that do the job of interacting with customers instead of paid bank employees. The task of these machines is to learn what each customer wants to do with their money and, to the extent that it is possible, act on what the customer wants (for example, ATMs can hand out cash). Customers can always know how much money they have in their accounts, and they are confident that the numbers they see in their bank statements and on their computer screens accurately reflect the number of dollars that they can get from the bank on demand. They can be so sure of this that they can accept those numbers in the same way they accept paper banknotes (this is similar to the way people started accepting paper dollars when they had been accepting gold or silver).

Such a system has several disadvantages:
* It is costly. [https://en.wikipedia.org/wiki/Electronic_funds_transfer EFTs] in Europe can cost 25 euros. Credit transactions can cost several percent of the transaction.
* It is slow. Checking and low cost wire services take days to complete.
* In most cases, it cannot be anonymous.
* Accounts can be frozen.
* Banks and other payment processors like PayPal, Visa, and Mastercard may refuse to process payments for legal entities.

Bitcoin is a system of owning and voluntarily transferring amounts of so-called ''bitcoins'', in a manner similar to an on-line banking, but pseudonymously and without reliance on a central authority to maintain account balances. If bitcoins are valuable, it is because they are useful and limited in supply.

==Bitcoin Basics==

===Creation of coins===
The creation of coins must be limited for the currency to have any value.

New coins are slowly [[Mining|mined]] into existence by following a mutually agreed-upon set of rules. A user [[Mining|mining]] bitcoins is running a software program that searches tirelessly for a solution to a very difficult math problem whose difficulty is precisely known. The difficulty is automatically adjusted regularly so that the number of solutions found globally, by everyone, is constant: an average of 6 per hour. When a solution is found, the user may tell everyone of the existence of this newly found solution, along with other information, packaged together in what is called a "[[Block|block]]".

Blocks contain 50 bitcoins at present. This amount, known as the block reward, is an incentive for people to perform the computation work required for generating blocks. Roughly every 4 years, the number of bitcoins that can be "mined" in a block reduces by 50%. Any block that is created by a malicious user that does not follow this rule (or any other rules) will be rejected by everyone else. In the end, no more than 21 million bitcoins will ever exist.

Because the block reward will decrease over the long term, miners will some day instead pay for their hardware and electricity costs by collecting [[Transaction_fee|transaction fees]]. The sender of money may voluntarily pay a small transaction fee which will be kept by whoever finds the next block. Paying this fee will encourage miners to include the transaction in a block more quickly.

===Sending payments===
To guarantee that a third-party, let's call her Eve, cannot spend other people's bitcoins by creating transactions in their names, Bitcoin uses [[Wikipedia:Public-key_cryptography|public key cryptography]] to make and verify digital signatures. In this system, each person, such as Alice or Bob, has one or more addresses each with an associated pair of public and private keys that they may hold in a [[Wallet|wallet]]. Only the user with the private key can sign a transaction to give some of their bitcoins to somebody else, but anyone can validate the signature using that user’s public key.

Suppose Alice wants to send a bitcoin to Bob.
* Bob sends his address (from which the public key can be derived) to Alice.
* Alice adds Bob’s public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Alice signs the transaction with her private key.
* Alice broadcasts the transaction on the Bitcoin network for all to see.

(Only the first two steps require human action. The rest is done by the Bitcoin client software.)

Looking at this transaction from the outside, anyone who knows that these addresses belong to Alice and Bob can see that Alice has agreed to transfer the amount to Bob, because nobody else has Alice's private key. Alice would be foolish to give her private key to other people, as this would allow them to sign transactions in her name, removing funds from her control.

Later on, when Bob wishes to transfer the same bitcoins to Charley, he will do the same thing:
* Charlie sends Bob his address.
* Bob adds Charlie's public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Bob signs the transaction with his private key.
* Bob broadcasts the transaction on the Bitcoin network for all to see.

Only Bob can do this because only he has the private key that can create a valid signature for the transaction.

Eve cannot change whose coins these are by replacing Bob’s public key with her public key, because Alice signed the transfer to Bob using her own private key, which is kept secret from Eve, and instructing that the coins which were hers now belong to Bob. So if Charlie accepts that the original coin was in the hands of Alice, he will also accept the fact that this coin was later passed to Bob, and now Bob is passing this same coin to him.

===Preventing [[double-spending]]===
The process described above does not prevent Alice from using the same bitcoins in more than one transaction. The following process does; this is the primary innovation behind Bitcoin.

* Details about the [[Transactions|transaction]] are [[Network|sent and forwarded]] to all or as many other computers as possible.
* A constantly growing chain of [[Blocks|blocks]] that contains a record of all transactions is collectively maintained by all computers (each has a full copy).
* To be accepted in the chain, transaction blocks must be valid and must include [[proof of work]] (one block generated by the network every 10 minutes).
* Blocks are chained in a way so that, if any one is modified, all following blocks will have to be recomputed.
* When multiple valid continuations to this chain appear, only the longest such branch is accepted and it is then extended further.

When Bob sees that his transaction has been included in a block, which has been made part of the single longest and fastest-growing block chain (extended with significant computational effort), he can be confident that the transaction by Alice has been accepted by the computers in the network and is permanently recorded, preventing Alice from creating a second transaction with the same coin. In order for Alice to thwart this system and double-spend her coins, she would need to muster more computing power than all other Bitcoin users combined.

===Anonymity===
When it comes to the Bitcoin network itself, there are no "accounts" to set up, and no e-mail addresses, user-names or passwords are required to hold or spend bitcoins. Each balance is simply associated with an address and its public-private key pair. The money "belongs" to anyone who has the private key and can sign transactions with it. Moreover, those keys do not have to be registered anywhere in advance, as they are only used when required for a transaction. Transacting parties do not need to know each other's identity in the same way that a store owner does not know a cash-paying customer's name.

A [[Address|Bitcoin address]] mathematically corresponds to a public key and looks like this:

:1PC9aZC4hNX2rmmrt7uHTfYAS3hRbph4UN

Each person can have many such addresses, each with its own balance, which makes it very difficult to know which person owns what amount. In order to protect his [[Anonymity|privacy]], Bob can generate a new public-private key pair for each individual receiving transaction and the Bitcoin software encourages this behavior by default. Continuing the example from above, when Charlie receives the bitcoins from Bob, Charlie will not be able to identify who owned the bitcoins before Bob.

===Capitalization / Nomenclature===
Since Bitcoin is both a currency and a protocol, capitalization of Bitcoin can be confusing. Generally accepted practice is to just use Bitcoin (singular, with upper case letter b) to describe the protocol and currency, together.

==Where to see and explore==
You can directly explore the system in action by visiting [http://blockchain.info/ Blockchain.info] or [http://blockexplorer.com/ Bitcoin Block Explorer].
The site shows you the latest blocks in the block chain. The [[Block_chain|block chain]] contains the agreed history of all transactions that took place in the system.
Note how many blocks were generated in the last hour, which on average will be 6. Also notice the number of transactions and the total amount transferred in the last hour (last time I checked it was about 64 and 15K).
This should give you an indication of how active the system is.

Next, navigate to one of these blocks.
The block's [[hash]] begins with a run of zeros. This is what made creating the block so difficult; a hash that begins with many zeros is much more difficult to find than a hash with few or no zeros. The computer that generated this block had to try many ''Nonce'' values (also listed on the block's page) until it found one that generated this run of zeros.
Next, see the line titled ''Previous block''. Each block contains the hash of the block that came before it. This is what forms the chain of blocks.
Now take a look at all the transactions the block contains. The first transaction is the income earned by the computer that generated this block. It includes a fixed amount of coins created out of "thin air" and possibly a fee collected from other transactions in the same block.

Drill down into any of the transactions and you will see how it is made up of one or more amounts coming in and out.
Having more than one incoming and outgoing amount in a transaction enables the system to join and break amounts in any possible way, allowing for any fractional amount needed. Each incoming amount is a past transaction (which you can also view) from someone's address, and each outgoing amount is addressed to someone and will be part of a future transaction (which you can also navigate down into if it has already taken place.)

Finally you can follow any of the [[Address|addresses]] links and see what public information is available for them.

To get an impression of the amount of activity on the Bitcoin network, you might like to visit the monitoring websites [[Bitcoin Monitor]] and [[Bitcoin Watch]]. The first shows a real-time visualization of events on the Bitcoin network, and the second lists general statistics on the amount and size of recent transactions.

===How many people use Bitcoin?===

This is quite a difficult question to answer accurately. One approach is to count how many bitcoin clients connected to the network in the last 24 hours. We can do this because some clients transmit their addresses to the other members of the network periodically. In September 2011 this method suggested that there were about {{formatnum:60000}} users.

==See Also==

* [http://www.youtube.com/watch?v=Um63OQz3bjo What is Bitcoin?] video introduction
* Installing Bitcoin [[getting started]]
* [[Using Bitcoin]]
* A gentle introduction to Bitcoin - [[BitcoinMe]]
* [http://coinlab.com/2011/12/bitcoin-primer Bitcoin Primer] from CoinLab
* Another introduction, ''The Rebooting Of Money'' podcast is found at [[Bitcoin Money]]
* A beginner's step-by-step guide to using Bitcoin, use of alternative wallets, and generally keeping your money and computer secure - [http://BitcoinIntro.com BitcoinIntro.com]
* [http://howtobitcoin.info howtobitcoin.info] Directory of bitcoin links for beginners
* Amazon Kindle Book [http://www.amazon.com/Bitcoin-Step-by-ebook/dp/B00A1CUQQU Bitcoin Step by Step] $3.99 (USD). The author walks you step by step through getting started.

[[zh-cn:简介]]

[[de:Einführung]]

Help:Introduction

2013-03-08T20:03:34Z

Atheros: Revert some changes by Jepo. Bad grammar.

The purpose of this page is to provide a general overview of the Bitcoin system and economy.

==Basic Concepts==

===Currency===

Alice wants to buy the [http://www.grasshillalpacas.com/alpacaproductsforbitcoinoffer.html Alpaca socks] which Bob has for sale. In return, she must provide something of equal value to Bob. The most efficient way to do this is by using a medium of exchange that Bob accepts which would be classified as currency. Currency makes trade easier by eliminating the need for [http://en.wikipedia.org/wiki/Coincidence_of_wants coincidence of wants] required in other systems of trade such as barter. Currency adoption and acceptance can be global, national, or in some cases local or community-based.

===Banks===

Alice need not provide currency to Bob in-person. She may instead transfer this value by first entrusting her currency to a bank who promises to store and protect Alice's currency notes. The bank gives Alice a written promise (called a "bank statement") that entitles her to withdraw the same number of currency bills that she deposited. Since the money is still Alice's, she is entitled to do with it whatever she pleases, and the bank (like most banks), for a small fee, will do Alice the service of passing on the currency bills to Bob on her behalf. This is done by Alice's bank by giving the dollar bills to Bob's bank and informing them that the money is for Bob, who will then see the amount the next time he checks his balance or receives his bank statement.

Since banks have many customers, and bank employees require money for doing the job of talking to people and signing documents, banks in recent times have been using machines such as ATMs and web servers that do the job of interacting with customers instead of paid bank employees. The task of these machines is to learn what each customer wants to do with their money and, to the extent that it is possible, act on what the customer wants (for example, ATMs can hand out cash). Customers can always know how much money they have in their accounts, and they are confident that the numbers they see in their bank statements and on their computer screens accurately reflect the number of dollars that they can get from the bank on demand. They can be so sure of this that they can accept those numbers in the same way they accept paper banknotes (this is similar to the way people started accepting paper dollars when they had been accepting gold or silver).

Such a system has several disadvantages:
* It is costly. [https://en.wikipedia.org/wiki/Electronic_funds_transfer EFTs] in Europe can cost 25 euros. Credit transactions can cost several percent of the transaction.
* It is slow. Checking and low cost wire services take days to complete.
* In most cases, it cannot be anonymous.
* Accounts can be frozen.
* Banks and other payment processors like PayPal, Visa, and Mastercard may refuse to process payments for legal entities.

Bitcoin is a system of owning and voluntarily transferring amounts of so-called ''bitcoins'', in a manner similar to an on-line banking, but pseudonymously and without reliance on a central authority to maintain account balances. If bitcoins are valuable, it is because they are useful and limited in supply.

==Bitcoin Basics==

===Creation of coins===
The creation of coins must be limited for the currency to have any value.

New coins are slowly [[Mining|mined]] into existence by following a mutually agreed-upon set of rules. A user [[Mining|mining]] bitcoins is running a software program that searches tirelessly for a solution to a very difficult math problem whose difficulty is precisely known. The difficulty is automatically adjusted regularly so that the number of solutions found globally, by everyone, is constant: an average of 6 per hour. When a solution is found, the user may tell everyone of the existence of this newly found solution, along with other information, packaged together in what is called a "[[Block|block]]".

Blocks contain 50 bitcoins at present. This amount, known as the block reward, is an incentive for people to perform the computation work required for generating blocks. Roughly every 4 years, the number of bitcoins that can be "mined" in a block reduces by 50%. Any block that is created by a malicious user that does not follow this rule (or any other rules) will be rejected by everyone else. In the end, no more than 21 million bitcoins will ever exist.

Because the block reward will decrease over the long term, miners will some day instead pay for their hardware and electricity costs by collecting [[Transaction_fee|transaction fees]]. The sender of money may voluntarily pay a small transaction fee which will be kept by whoever finds the next block. Paying this fee will encourage miners to include the transaction in a block more quickly.

===Sending payments===
To guarantee that a third-party, let's call her Eve, cannot spend other people's bitcoins by creating transactions in their names, Bitcoin uses [[Wikipedia:Public-key_cryptography|public key cryptography]] to make and verify digital signatures. In this system, each person, such as Alice or Bob, has one or more addresses each with an associated pair of public and private keys that they may hold in a [[Wallet|wallet]]. Only the user with the private key can sign a transaction to give some of their bitcoins to somebody else, but anyone can validate the signature using that user’s public key.

Suppose Alice wants to send a bitcoin to Bob.
* Bob sends his address (from which the public key can be derived) to Alice.
* Alice adds Bob’s public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Alice signs the transaction with her private key.
* Alice broadcasts the transaction on the Bitcoin network for all to see.

(Only the first two steps require human action. The rest is done by the Bitcoin client software.)

Looking at this transaction from the outside, anyone who knows that these addresses belong to Alice and Bob can see that Alice has agreed to transfer the amount to Bob, because nobody else has Alice's private key. Alice would be foolish to give her private key to other people, as this would allow them to sign transactions in her name, removing funds from her control.

Later on, when Bob wishes to transfer the same bitcoins to Charley, he will do the same thing:
* Charlie sends Bob his address.
* Bob adds Charlie's public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Bob signs the transaction with his private key.
* Bob broadcasts the transaction on the Bitcoin network for all to see.

Only Bob can do this because only he has the private key that can create a valid signature for the transaction.

Eve cannot change whose coins these are by replacing Bob’s public key with her public key, because Alice signed the transfer to Bob using her own private key, which is kept secret from Eve, and instructing that the coins which were hers now belong to Bob. So if Charlie accepts that the original coin was in the hands of Alice, he will also accept the fact that this coin was later passed to Bob, and now Bob is passing this same coin to him.

===Preventing [[double-spending]]===
The process described above does not prevent Alice from using the same bitcoins in more than one transaction. The following process does; this is the primary innovation behind Bitcoin.

* Details about the [[Transactions|transaction]] are [[Network|sent and forwarded]] to all or as many other computers as possible.
* A constantly growing chain of [[Blocks|blocks]] that contains a record of all transactions is collectively maintained by all computers (each has a full copy).
* To be accepted in the chain, transaction blocks must be valid and must include [[proof of work]] (one block generated by the network every 10 minutes).
* Blocks are chained in a way so that, if any one is modified, all following blocks will have to be recomputed.
* When multiple valid continuations to this chain appear, only the longest such branch is accepted and it is then extended further.

When Bob sees that his transaction has been included in a block, which has been made part of the single longest and fastest-growing block chain (extended with significant computational effort), he can be confident that the transaction by Alice has been accepted by the computers in the network and is permanently recorded, preventing Alice from creating a second transaction with the same coin. In order for Alice to thwart this system and double-spend her coins, she would need to muster more computing power than all other Bitcoin users combined.

===Anonymity===
When it comes to the Bitcoin network itself, there are no "accounts" to set up, and no e-mail addresses, user-names or passwords are required to hold or spend bitcoins. Each balance is simply associated with an address and its public-private key pair. The money "belongs" to anyone who has the private key and can sign transactions with it. Moreover, those keys do not have to be registered anywhere in advance, as they are only used when required for a transaction. Transacting parties do not need to know each other's identity in the same way that a store owner does not know a cash-paying customer's name.

A [[Address|Bitcoin address]] mathematically corresponds to a public key and looks like this:

:1PC9aZC4hNX2rmmrt7uHTfYAS3hRbph4UN

Each person can have many such addresses, each with its own balance, which makes it very difficult to know which person owns what amount. In order to protect his [[Anonymity|privacy]], Bob can generate a new public-private key pair for each individual receiving transaction and the Bitcoin software encourages this behavior by default. Continuing the example from above, when Charlie receives the bitcoins from Bob, Charlie will not be able to identify who owned the bitcoins before Bob without further information.

===Capitalization / Nomenclature===
Since Bitcoin is both a currency and a protocol, capitalization of Bitcoin can be confusing. Generally accepted practice is to just use Bitcoin (singular, with upper case letter b) to describe the protocol and currency, together.

==Where to see and explore==
You can directly explore the system in action by visiting [http://blockchain.info/ Blockchain.info] or [http://blockexplorer.com/ Bitcoin Block Explorer].
The site shows you the latest blocks in the block chain. The [[Block_chain|block chain]] contains the agreed history of all transactions that took place in the system.
Note how many blocks were generated in the last hour, which on average will be 6. Also notice the number of transactions and the total amount transferred in the last hour (last time I checked it was about 64 and 15K).
This should give you an indication of how active the system is.

Next, navigate to one of these blocks.
The block's [[hash]] begins with a run of zeros. This is what made creating the block so difficult; a hash that begins with many zeros is much more difficult to find than a hash with few or no zeros. The computer that generated this block had to try many ''Nonce'' values (also listed on the block's page) until it found one that generated this run of zeros.
Next, see the line titled ''Previous block''. Each block contains the hash of the block that came before it. This is what forms the chain of blocks.
Now take a look at all the transactions the block contains. The first transaction is the income earned by the computer that generated this block. It includes a fixed amount of coins created out of "thin air" and possibly a fee collected from other transactions in the same block.

Drill down into any of the transactions and you will see how it is made up of one or more amounts coming in and out.
Having more than one incoming and outgoing amount in a transaction enables the system to join and break amounts in any possible way, allowing for any fractional amount needed. Each incoming amount is a past transaction (which you can also view) from someone's address, and each outgoing amount is addressed to someone and will be part of a future transaction (which you can also navigate down into if it has already taken place.)

Finally you can follow any of the [[Address|addresses]] links and see what public information is available for them.

To get an impression of the amount of activity on the Bitcoin network, you might like to visit the monitoring websites [[Bitcoin Monitor]] and [[Bitcoin Watch]]. The first shows a real-time visualization of events on the Bitcoin network, and the second lists general statistics on the amount and size of recent transactions.

===How many people use Bitcoin?===

This is quite a difficult question to answer accurately. One approach is to count how many bitcoin clients connected to the network in the last 24 hours. We can do this because some clients transmit their addresses to the other members of the network periodically. In September 2011 this method suggested that there were about {{formatnum:60000}} users.

==See Also==

* [http://www.youtube.com/watch?v=Um63OQz3bjo What is Bitcoin?] video introduction
* Installing Bitcoin [[getting started]]
* [[Using Bitcoin]]
* A gentle introduction to Bitcoin - [[BitcoinMe]]
* [http://coinlab.com/2011/12/bitcoin-primer Bitcoin Primer] from CoinLab
* Another introduction, ''The Rebooting Of Money'' podcast is found at [[Bitcoin Money]]
* A beginner's step-by-step guide to using Bitcoin, use of alternative wallets, and generally keeping your money and computer secure - [http://BitcoinIntro.com BitcoinIntro.com]
* [http://howtobitcoin.info howtobitcoin.info] Directory of bitcoin links for beginners
* Amazon Kindle Book [http://www.amazon.com/Bitcoin-Step-by-ebook/dp/B00A1CUQQU Bitcoin Step by Step] $3.99 (USD). The author walks you step by step through getting started.

[[zh-cn:简介]]

[[de:Einführung]]

Irreversible Transactions

2013-03-08T19:52:42Z

Atheros: Removed bad page.

Double-spending is the result of successfully spending some money more than once. Bitcoin protects against double spending by verifying each transaction added to the [[block chain]] to ensure that the inputs for the transaction had not previously already been spent.

Other electronic systems prevent double-spending by having a master authoritative source that follows business rules for authorizing each transaction. Bitcoin uses a decentralized system, where a consensus among nodes following the same protocol is substituted for a central authority.

Bitcoin has some exposure to fraudulent double-spending when a transaction is first made, with less and less risk as a transaction gains [[confirmation|confirmations]].

==Attack vectors==

===Race attack===

Traders and merchants who accept a payment immediately on seeing "0/unconfirmed" are exposed to a double-spend occurring is there was a fraudulent attempt that successfully communicated one transaction to the merchant yet communicated a different transaction that spends the same coin that was first to eventually make it into the block chain.

Merchants can take precautions (e.g., disable incoming connections, only connect to well connected nodes) to lessen the risk of a race attack but the risk cannot be eliminated. Therefore, the cost/benefit of the risk needs to be considered when accepting payment on 0/unconfirmed when there is no recourse against the attacker.

The [[research]] paper [http://eprint.iacr.org/2012/248.pdf Two Bitcoins at the Price of One] finds that the protocol allows a high degree of success by an attacker in performing race attacks. The method studied in the research paper depends on access to the merchant's Bitcoin node which is why that even prior to this paper, recommendations for merchants include disabling incoming connections and to choose specific outgoing connections<ref>[http://bitcointalk.org/index.php?topic=79090.msg881283#msg881283 BitcoinTalk Thread - Two Bitcoins at the Price of One]</ref>.

===Finney attack===

Another attack the trader or merchant is exposed to when accepting payment on 0/unconfirmed. The Finney attack is a fraudulent double-spend that requires the participation of a miner once a block has been mined<ref>[http://www.bitcointalk.org/index.php?topic=3441.msg48384#msg48384 Best practice for fast transaction acceptance - how high is the risk?]</ref>. The risk of a Finney attack cannot be eliminated regardless of the precautions taken by the merchant, but the participation of a miner is required and a specific sequence of events must occur. Thus the attack is not trivial nor inexpensive to perform and only makes sense for the attacker when the gains from the attack are significant. Just like with the race attack, a trader or merchant should consider the cost / benefit when accepting payment on just one confirmation when there is no recourse against the attacker.

===Vector76 attack===

Also referred to as a one-confirmation attack, is a combination of the race attack and the Finney attack such that a transaction that even has one confirmation can still be double-spent. The same protective action for the race attack (no incoming connections, explicit outgoing connection to a well-connected node) significantly reduces the risk of this occurring.

===Brute force attack===

This attack has a chance to work even if the merchant waits for some confirmations, but requires relatively high hashrate.

The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining a blockchain fork in which a double-spending transaction is included instead. After waiting for ''n'' confirmations, the merchant sends the product. If the attacker happened to find more than ''n'' blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network. If he never manages to do this, the attack fails and the payment to the merchant will go through.

The probability of success is a function of the attacker's hashrate (as a proportion of the total network hashrate) and the number of confirmations the merchant waits for. For example, if the attacker controls 10% of the network hashrate but the merchant waits for 6 confirmations, the success probability is on the order of 0.1%.

===>50% attack===

If the attacker controls more than half of the network hashrate, the previous attack has a probability of 100% to succeed. Since the attacker can generate blocks faster than the rest of the network, he can simply persevere with his private fork until it becomes longer than the branch built by the honest network, from whatever disadvantage.

No amount of confirmations can prevent this attack; however, waiting for confirmations does increase the aggregate resource cost of performing the attack, which could make it unprofitable or delay it long enough for the circumstances to change or slower-acting synchronization methods to kick in.

==Risk management==

There are third-party services to assist traders and merchants to help manage the risk or to insure against losses.

==See Also==

* [[Weaknesses]]
* [http://codinginmysleep.com/bitcoin-attacks-in-plain-english Bitcoin Attacks in Plain English] by David Perry

[[de:Doppelausgaben]]

==References==
<references />

[[Category:Technical]]

Public relations

2013-03-08T19:52:26Z

Atheros: Removed bad page.

'''Public relations''' is about how Bitcoin is presented to the world. The mathematical foundations of Bitcoin minimize the level of trust necessary to use it, but for anyone who isn't interested in cryptography the strength of the Bitcoin brand is more important.

This page lists some community-developed talking points, so if you'd like to promote Bitcoin consider using them.

==Terminology==

Bitcoin is a ''crypto-currency'', that is, a currency based on cryptography. However the crypto- prefix has another meaning, "something whose nature is obfuscated", as in cryptic messages. In that sense the term may not intuitively reflect the open source and community-based nature of the project. Also, cryptography is correctly perceived by many as a difficult and highly academic form of mathematics, which makes the term crypto-currency sound intimidating.

There are various alternatives, but many don't translate well into other languages or have other undesirable connotations.

'''Do say'''
* Bitcoin is an [[digital currency|internet currency.]] This is an accurate description and combines two everyday concepts people are familiar with.
* Bitcoin is a decentralized currency. This emphasizes the primary difference to regular, state backed currencies.
* Bitcoin is a predictable currency, stressing the open nature of the algorithms and number there will be
* Bitcoin is open source, demonstrating the community feeling of the currency
* Bitcoin is getting stronger every day. Try and mention news stories and the current [[MtGox]] rates.

'''Don't say'''
* Bitcoin is a crypto-currency, grassroots currency, "currency of the people" etc. All these are loaded terms that may color peoples perceptions or translate badly into other languages.

==Benefits==

Bitcoin has many benefits over more traditional payment systems. Many of them can be summed up in one word: flexibility. Everyone likes flexibility, as long as it isn't too hard to deal with.

'''Do say'''
* Bitcoins can be stored with a bank or financial institution just like existing currencies if you want, but you're free to explore alternatives right up to and including entirely bank-free operation. After the financial crisis, disillusionment with banks is widespread and this aspect may appeal to some (not all).
* Bitcoin can reduce the costs of everyday goods, by making the financial markets more competitive and eliminating the risk premium that credit card transactions entail.
* Bitcoin is fair: it's as easy for you to sell things as buy them. Contrast with most existing payment systems in which accepting payments is much harder than making them.
* Bitcoin has strong privacy: you should be able to choose who knows about your financial transactions. There are no statements mailed to you detailing your every financial move.
* Bitcoin makes it easier to sell things over the internet. Most people aren't familiar with the myriad difficulties in this seemingly simple task.

'''Don't say'''
* Bitcoin transactions are free. They usually are today, but there are a few cases where a small fee is required. And in future fees will play a larger role. It's hard to predict what level fees will end up at, as they are paying for something entirely different to existing systems. There are good reasons to believe Bitcoin transactions will always be cheaper than most financial transactions are today, but the arguments on this topic are complex.
* Bitcoin can't be taxed. Tax collectors were around before electronic payments and they'll be around after Bitcoin.
* Bitcoin is anonymous. [[Anonymity]] and Bitcoin is a complex topic, and anonymity means something slightly different to privacy.

==Politics and the law==

Bitcoin appeals to many libertarians, a political movement that emphasizes minimal government and individualism. If you are such a person, it's tempting to frame Bitcoin as some kind of anti-government force. But right or wrong many people are turned off by politics, and many others don't have an anti-government world view. This is especially true in Europe.

'''Do say'''
* Bitcoin is a chance to revolutionize the financial system, making it fairer and more democratic.
* Bitcoin offers a strong level of privacy, but the people you trade with still know who you are. If the police turn up with the right warrants, they will probably learn who owns particular addresses. This means lawbreakers can still be tracked down with sufficient effort. As an analogy you can use the internet itself - whilst the average person and even large corporations can't find out the real identity behind an IP address, the law can make everyone work together to identify the owner.
* Bitcoin allows anyone to pay anyone else. The authority to spend bitcoins belongs solely to the owner of the bitcoins. They decide and are responsible for the legality and morality of their actions, not a central authority.

'''Don't say'''
* Bitcoin is a way to topple or restrict the power of governments.
* Bitcoin is impossible to regulate or control. There are schemes in which by regulating miners, Bitcoins can be frozen much as assets are sometimes frozen today. It's hard to know if they will ever be implemented, but it's not the case that Bitcoin cannot be regulated.
* Bitcoin cannot be outlawed. There aren't any laws that would make Bitcoin obviously illegal, however, financial regulation is an extremely complex topic and it's possible that individual companies, exchanges etc, may at some point be found to not be in compliance. This happens to large, well-respected financial institutions so it's unreasonable to expect it will never happen to something Bitcoin related.

==Expectations==

Starting around the middle of 2010, Bitcoin has experienced dramatic growth in both the size of its community and exchange rates. People who are naturally optimistic or enthusiastic about Bitcoin sometimes try to promote it as a kind of get-rich-quick scheme.

'''Do say'''
* Bitcoin is an experiment that has grown rapidly as interest in the idea spreads.
* There are many people trading real goods and services with Bitcoins.
* Whilst the fundamental idea of Bitcoin is sound, pricing it is hard because nobody really knows the future potential. As a result the value swings wildly back and forth.
* Although speculation of Bitcoins' value is possible and many are doing it, hoarding coins is an extremely risky investment strategy. Like many risky investments, it has potentially high returns but losses could be severe.
* Whilst Bitcoin might fail, the concept of internet currencies is here to stay.

'''Don't say'''
* Bitcoins value has only gone up. Whilst the long term trend has been up, exchange rates are highly volatile and go down frequently.
* Get in now before it's too late. This makes Bitcoin sound like a scam.
* Bitcoin will take over the world unless <foo>. There are many potential end-games for Bitcoin of which "taking over the world" or "absolute failure" are only two. It could just as easily end up stuck in a niche, becoming an established competitor in the internet payments space but not going beyond that, etc.

==Economics==

Bitcoin uses a simple and easy to understand economic model, that is quite different to the one used by regular state-backed currencies today. Many people who just want to use the currency won't be interested in this aspect of the system. If they are:

'''Do say'''
* Bitcoin is intended to have a stable quantity of coins in existence in the long run.
* Bitcoin inflates rapidly at present because the system is young. Over many decades, inflation will slow and eventually stop.
* Assuming the (Bitcoin using) economy grows, that means that after some decades of operation, the value of a single Bitcoin will increase at roughly the same rate as the economy itself.
* A growing economy with a static currency behaves, to the end user, much like a growing economy in which you put your money into an interest-bearing account. The value increases slowly over time, but you can usually earn more by investing in higher-risk ventures.
* If it comes up, the usual formulation of the deflationary spiral argument (people won't spend money because it's always worth more tomorrow) is over-simplified. Consider consumer electronics, in which waiting a few months practically guarantees you something better for the same money. The actual economic argument, which is valid, has to do with the way existing currencies are expanded via the issuance of debt. Bitcoins are not issued via loans so the argument doesn't apply in the same way.

'''Don't say'''
* Bitcoin is deflationary. This implies the total amount of currency is intended to shrink. After inflation eventually shuts down, the currency will shrink at a very slow rate due to natural erosion, ie, people losing their wallet files due to failed hardware and missing backups (or simply losing interest and exiting the system). But this is better described as unavoidable than intentional.
* There are 21 million coins. The Bitcoin definition of a coin is very unintuitive: it's a unit that can be divided into 100,000,000 pieces. If you want to discuss the exact limit, be sure to clarify that whilst we talk about "bitcoins", the placement of the decimal point is arbitrary and was chosen for convenience.

==Notes and Addenda==

It should be noted that the way you present the currency greatly depends on your audience. If the person you are speaking to is not an anarchist or anyone too much into anonymity, don't mention these aspects of the community. Tailor the way you present the currency to the interests of the audience.

''e.g. Do not mention that you can buy all sorts of drugs untraceably at a geriatric knitting convention''

==See Also==

* [[:Category:Marketing|Marketing]]

[[Category:Marketing|Marketing]]

Help:Introduction

2013-03-08T19:51:53Z

Atheros: /* See Also */ Removed bad page.

The purpose of this page is to provide a general overview of the Bitcoin system and economy.

==Basic Concepts==

===Currency===

Alice wants to buy the [http://www.grasshillalpacas.com/alpacaproductsforbitcoinoffer.html Alpaca socks] which Bob has for sale. In return, she is to provide something of equal value to Bob. The most efficient way to do this is by using a medium of exchange that Bob accepts which would be classified as currency. Currency makes trade easier by eliminating the need for [http://en.wikipedia.org/wiki/Coincidence_of_wants coincidence of wants] required in other systems of trade such as barter. Currency adoption and acceptance can be global, national, or in some cases local or community-based.

===Banks===

Alice needs not provide currency to Bob in-person. She may instead transfer this value by first entrusting her currency to a bank who promises to store and protect Alice's currency notes. The bank gives Alice a written promise (called a "bank statement") that entitles her to withdraw the same number of currency bills that she deposited. Since the money is still Alice's, she is entitled to do with it whatever she pleases, and the bank (like most banks), for a small fee, will do Alice the service of passing on the currency bills to Bob on her behalf. This is done by Alice's bank by giving the dollar bills to Bob's bank and informing them that the money is for Bob, who will then see the amount the next time he checks his balance or receives his bank statement.

Since banks have many customers, and bank employees require money for doing the job of talking to people and signing documents, banks in recent times have been using machines such as ATMs and web servers that do the job of interacting with customers instead of paid bank employees. The task of these machines is to learn what each customer wants to do with their money and, to the extent that it is possible, act on what the customer wants (for example, ATMs can hand out cash). Customers can always know how much money they have in their accounts, and they are confident that the numbers they see in their bank statements and on their computer screens accurately reflect the number of dollars that they can get from the bank on demand. They can be so sure of this that they can accept those numbers in the same way they accept paper banknotes (this is similar to the way people started accepting paper dollars when they had been accepting gold or silver).

Such a system has several disadvantages:
* It is costly. [https://en.wikipedia.org/wiki/Electronic_funds_transfer EFTs] in Europe can cost 25 euros. Credit transactions can cost several percent of the transaction.
* It is slow. Checking and low cost wire services take days to complete.
* In most cases, it cannot be anonymous.
* Accounts can be frozen.
* Banks and other payment processors like PayPal, Visa, and Mastercard may refuse to process payments for legal entities.

Bitcoin is a system of owning and voluntarily transferring amounts of so-called ''bitcoins'', in a manner similar to an on-line banking, but pseudonymously and without reliance on a central authority to maintain account balances. If bitcoins are valuable, it is because they are useful and limited in supply.

==Bitcoin Basics==

===Creation of coins===
The creation of coins must be limited for the currency to have any value.

New coins are slowly [[Mining|mined]] into existence by following a mutually agreed-upon set of rules. A user [[Mining|mining]] bitcoins is running a software program that searches tirelessly for a solution to a very difficult math problem whose difficulty is precisely known. The difficulty is automatically adjusted regularly so that the number of solutions found globally, by everyone, is constant: an average of 6 per hour. When a solution is found, the user may tell everyone of the existence of this newly found solution, along with other information, packaged together in what is called a "[[Block|block]]".

Blocks contain 50 bitcoins at present. This amount, known as the block reward, is an incentive for people to perform the computation work required for generating blocks. Roughly every 4 years, the number of bitcoins that can be "mined" in a block reduces by 50%. Any block that is created by a malicious user that does not follow this rule (or any other rules) will be rejected by everyone else. In the end, no more than 21 million bitcoins will ever exist.

Because the block reward will decrease over the long term, miners will some day instead pay for their hardware and electricity costs by collecting [[Transaction_fee|transaction fees]]. The sender of money may voluntarily pay a small transaction fee which will be kept by whomever finds the next block. Paying this fee will encourage miners to include the transaction in a block more quickly.

===Sending payments===
To guarantee that a third-party, let's call her Eve, cannot spend other people's bitcoins by creating transactions in their names, Bitcoin uses [[Wikipedia:Public-key_cryptography|public key cryptography]] to make and verify digital signatures. In this system, each person, such as Alice or Bob, has one or more addresses each with an associated pair of public and private keys that they may hold in a [[Wallet|wallet]]. Only the user with the private key can sign a transaction to give some of their bitcoins to somebody else, but anyone can validate the signature using that user’s public key.

Suppose Alice wants to send a bitcoin to Bob.
* Bob sends his address (from which the public key can be derived) to Alice.
* Alice adds Bob’s public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Alice signs the transaction with her private key.
* Alice broadcasts the transaction on the Bitcoin network for all to see.

(Only the first two steps require human action. The rest is done by the Bitcoin client software.)

Looking at this transaction from the outside, anyone who knows that these addresses belong to Alice and Bob can see that Alice has agreed to transfer the amount to Bob, because nobody else has Alice's private key. Alice would be foolish to give her private key to other people, as this would allow them to sign transactions in her name, removing funds from her control.

Later on, when Bob wishes to transfer the same bitcoins to Charley, he will do the same thing:
* Charlie sends Bob his address.
* Bob adds Charlie's public key and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Bob signs the transaction with his private key.
* Bob broadcasts the transaction on the Bitcoin network for all to see.

Only Bob can do this because only he has the private key that can create a valid signature for the transaction.

Eve cannot change whose coins these are by replacing Bob’s public key with her public key, because Alice signed the transfer to Bob using her own private key, which is kept secret from Eve, and instructing that the coins which were hers now belong to Bob. So if Charlie accepts that the original coin was in the hands of Alice, he will also accept the fact that this coin was later passed to Bob, and now Bob is passing this same coin to him.

===Preventing [[double-spending]]===
The process described above does not prevent Alice from using the same bitcoins in more than one transaction. The following process does; this is the primary innovation behind Bitcoin.

* Details about the [[Transactions|transaction]] are [[Network|sent and forwarded]] to all or as many other computers as possible.
* A constantly growing chain of [[Blocks|blocks]] that contains a record of all transactions is collectively maintained by all computers (each has a full copy).
* To be accepted in the chain, transaction blocks must be valid and must include [[proof of work]] (one block generated by the network every 10 minutes).
* Blocks are chained in a way so that, if any one is modified, all following blocks will have to be recomputed.
* When multiple valid continuations to this chain appear, only the longest such branch is accepted and it is then extended further.

When Bob sees that his transaction has been included in a block, which has been made part of the single longest and fastest-growing block chain (extended with significant computational effort), he can be confident that the transaction by Alice has been accepted by the computers in the network and is permanently recorded, preventing Alice from creating a second transaction with the same coin. In order for Alice to thwart this system and double-spend her coins, she would need to muster more computing power than all other Bitcoin users combined.

===Anonymity===
When it comes to the Bitcoin network itself, there are no "accounts" to set up, and no e-mail addresses, user-names or passwords are required to hold or spend bitcoins. Each balance is simply associated with an address and its public-private key pair. The money "belongs" to anyone who has the private key and can sign transactions with it. Moreover, those keys do not have to be registered anywhere in advance, as they are only used when required for a transaction. Transacting parties do not need to know each other's identity in much the same way that a store owner does not know a cash-paying customer's name.

A [[Address|Bitcoin address]] mathematically corresponds to a public key and looks like this:

:1PC9aZC4hNX2rmmrt7uHTfYAS3hRbph4UN

Each person can have many such addresses, each with its own balance, which makes it very difficult to know which person owns what amount. In order to protect his [[Anonymity|privacy]], Bob can generate a new public-private key pair for each individual receiving transaction and the Bitcoin software encourages this behavior by default. Continuing the example from above, when Charlie receives the bitcoins from Bob, Charlie will not be able to identify who owned the bitcoins before Bob without further information.

===Capitalization / Nomenclature===
Since Bitcoin is both a currency and a protocol, capitalization of Bitcoin can be confusing. Generally accepted practice is to just use Bitcoin (singular, with upper case letter b) to describe the protocol and currency, together.

==Where to see and explore==
You can directly explore the system in action by visiting [http://blockchain.info/ Blockchain.info] or [http://blockexplorer.com/ Bitcoin Block Explorer].
The site shows you the latest blocks in the block chain. The [[Block_chain|block chain]] contains the agreed history of all transactions that took place in the system.
Note how many blocks were generated in the last hour, which on average will be 6. Also notice the number of transactions and the total amount transferred in the last hour (last time I checked it was about 64 and 15K).
This should give you an indication of how active the system is.

Next, navigate to one of these blocks.
The block's [[hash]] begins with a run of zeros. This is what made creating the block so difficult; a hash that begins with many zeros is much more difficult to find than a hash with few or no zeros. The computer that generated this block had to try many ''Nonce'' values (also listed on the block's page) until it found one that generated this run of zeros.
Next, see the line titled ''Previous block''. Each block contains the hash of the block that came before it. This is what forms the chain of blocks.
Now take a look at all the transactions the block contains. The first transaction is the income earned by the computer that generated this block. It includes a fixed amount of coins created out of "thin air" and possibly a fee collected from other transactions in the same block.

Drill down into any of the transactions and you will see how it is made up of one or more amounts coming in and out.
Having more than one incoming and outgoing amount in a transaction enables the system to join and break amounts in any possible way, allowing for any fractional amount needed. Each incoming amount is a past transaction (which you can also view) from someone's address, and each outgoing amount is addressed to someone and will be part of a future transaction (which you can also navigate down into if it has already taken place.)

Finally you can follow any of the [[Address|addresses]] links and see what public information is available for them.

To get an impression of the amount of activity on the Bitcoin network, you might like to visit the monitoring websites [[Bitcoin Monitor]] and [[Bitcoin Watch]]. The first shows a real-time visualization of events on the Bitcoin network, and the second lists general statistics on the amount and size of recent transactions.

===How many people use Bitcoin?===

This is quite a difficult question to answer accurately. One approach is to count how many bitcoin clients connected to the network in the last 24 hours. We can do this because some clients transmit their addresses to the other members of the network periodically. In September 2011 this method suggested that there were about {{formatnum:60000}} users.

==See Also==

* [http://www.youtube.com/watch?v=Um63OQz3bjo What is Bitcoin?] video introduction
* Installing Bitcoin [[getting started]]
* [[Using Bitcoin]]
* A gentle introduction to Bitcoin - [[BitcoinMe]]
* [http://coinlab.com/2011/12/bitcoin-primer Bitcoin Primer] from CoinLab
* Another introduction, ''The Rebooting Of Money'' podcast is found at [[Bitcoin Money]]
* A beginner's step-by-step guide to using Bitcoin, use of alternative wallets, and generally keeping your money and computer secure - [http://BitcoinIntro.com BitcoinIntro.com]
* [http://howtobitcoin.info howtobitcoin.info] Directory of bitcoin links for beginners
* Amazon Kindle Book [http://www.amazon.com/Bitcoin-Step-by-ebook/dp/B00A1CUQQU Bitcoin Step by Step] $3.99 (USD). The author walks you step by step through getting started.

[[zh-cn:简介]]

[[de:Einführung]]

Using Bitcoin

2013-03-08T19:51:10Z

Atheros: Removed bad page.

<div style="background:#dddddd;border:solid gray 1px;width:70%;margin:auto;">
Current releases of the bitcoin client have a different user interface than the versions used in this article.

This article could use an update. See the discussion for this article for more.
</div>

This page is a detailed tutorial to help new users understand and using bitcoin. After you read this page, you'll know the basics of what bitcoin is and how it is structured, how to get and install the bitcoin client, where to get coins, and how to use the client to send and receive transactions.

If you want to ignore all the details of how the system works, and just want to start using it, see the [[Getting started]] page instead.

=What is Bitcoin=

Bitcoin is a distributed [[digital currency]] based on strong cryptographic principles. Each coin is assigned to the owner's public key, and is transferrable via cryptographically signed messages.

=Getting started=

In this section, you'll learn where to get the client, how to install it on different operating systems, and download the [[block chain]].

==Download and install the client==

First, download the bitcoin client from http://bitcoin.org/. Choose the appropriate link depending on your operating system, and install in the usual manner. For Windows, easiest is probably the executable installer. For Linux, note that the tar.gz contains the binary build, in addition to the source, so if you run a recent distribution, you should be able to just run the binary without compiling yourself.

==Starting the client and connecting to the network==

[[File:First time run fin.png|400px|thumb|right|Bitcoin is initializing by establishing a connection to other clients and downloading the blocks.]]
Bitcoin comes with a GUI client called "bitcoin", and a CLI (text-mode) client called "bitcoind". It is probably more user-friendly to start with the GUI, so launch the bitcoin client.

When you start for the first time, your bitcoin wallet will be created automatically, and the client will attempt to establish connections to other nodes on the network and start downloading the bitcoin [[block chain]]. You must get all of the blocks in the chain before sending/receiving transactions. [http://blockexplorer.com/q/getblockcount Click here] to see the current number of blocks in the chain. This download may take as long as several hours.

==Client features==

Your starting bitcoin address (you can have as many as you want - we'll talk about [[#Bitcoin addresses|addresses]] later) shows in a text box at the top. Right below it is your total bitcoin balance, which, of course, to start with will be zero. There is a list box below it showing all your transactions, which can be variously filtered with tabs, which again will be empty to start with.

The status bar at the bottom will display some important information. If you have [[#Generating bitcoins|bitcoin generation (block hashing)]] turned on, on the left the client will display your hash rate. To the right of that, you will see the number of bitcoin nodes your client is connected to, then, the number of blocks your client has in its chain, and finally, the number of transactions you have in your wallet.

=Using bitcoin=

In this section you will learn about bitcoin addresses, sending and receiving transactions, the block chain and transaction confirmations, where to get your first bitcoins (faucet), generation. Tips on keeping wallet safe.

==Getting your first bitcoins==

There are few things more exciting than getting your first bitcoins! So once you have all the blocks downloaded, head on over to the [https://freebitcoins.appspot.com/ bitcoin faucet], fill out the form and put in your bitcoin address, and receive some free bitcoin! (You can do this before finishing the block chain download, but you won't see the coins in your wallet until you finish downloading the blocks... which would put a damper on the whole excitement bit.)

See [http://en.bitcoin.it/wiki/Trade#Samples_and_Marketing_Offers Samples and Marketing Offers] for other free bitcoins and marketing offers.

Once you submit the form successfully, you should see a new transaction in your client within seconds. But it will be grayed out, and have 0/unconfirmed status:
[[File:First btc recv.png|frame|none]]

Once your transaction makes it into the block chain, the confirmation count will grow in step with the number of blocks in the chain. By default, the client stops showing "unconfirmed" after the transaction is 6 blocks deep in the chain:
[[File:Six confirms bitcoin client.png|frame|none]]

==Transaction confirmations==

write about [[Blocks|blocks]] and [[Confirmation|confirmations]] here.

thanks to the [[Block chain|block chain]], you don't need to be online for receiving BTC...

==Bitcoin addresses==

You can create as many new addresses as you like. Using a different address each time helps to preserve your [[anonymity]].

You cannot send BTC to an invalid address. Client will refuse to send payment to a misspecified address. (Though with care you can craft a valid but nonexistent address.)

talk more about addresses here

==Generating bitcoins==

talk about generation here

=See also=

* [[Getting started]] A brief tutorial for the impatient

[[Category:Introduction]]

Bitcoin

2013-03-08T19:50:29Z

Atheros: Removed bad page.

'''Bitcoin''' is a decentralized [[digital currency]] created by developer [[Satoshi Nakamoto]]. It does not rely on a central server to process transactions or store funds. There are a maximum of 2,100,000,000,000,000 Bitcoin elements (called satoshis), currently most commonly measured in units of 100,000,000 known as BTC.

It is the most widely used alternative currency,<ref name="Quantitative Analysis of the Full Bitcoin Transaction Graph">{{cite web|title=Quantitative Analysis of the Full Bitcoin Transaction Graph|url=http://eprint.iacr.org/2012/584.pdf|publisher=Cryptology ePrint Archive|accessdate=18 October 2012|author=Ron Dorit|coauthors=Adi Shamir|page=17|quote=The Bitcoin system is the best known and most widely used alternative payment scheme,...}}</ref> with the total market cap at over 100 million US dollars.<ref>{{cite web|last=Koch|first=Rüdiger|title=Bitcoin - a Means for Redistribution of Wealth|url=http://ieet.org/index.php/IEET/more/koch20120927|publisher=Institute for Ethics & Emerging Technologies|accessdate=27 October 2012|quote=We’re currently at 50,000 users and a market cap of $100 Million.}}</ref><ref>{{cite web|title=Market Capitalization|url=http://blockchain.info/charts/market-cap|publisher=Blockchain.info|accessdate=28 October 2012}}</ref><ref name="Mt.Gox data">{{Cite web|title=Mt.Gox data|url=http://bitcoincharts.com/markets/mtgoxUSD.html|publisher=Bitcoincharts}}</ref>

Bitcoin has no central issuer; instead, the peer-to-peer network regulates Bitcoins, transactions and issuance according to consensus in network software.
Bitcoins are issued to various nodes that verify transactions through computing power;
it is established that there will be a limited and scheduled release of no more than 21 million BTC worth of coins, which will be fully issued by the year 2140.

Internationally, Bitcoins can be exchanged and managed through various websites and [[software]] along with physical banknotes and coins.<ref>{{Cite web|title=Physical Bitcoins by Casascius|url=https://www.casascius.com/|publisher=Casascius Coins|accessdate=29 September 2012}}</ref><ref>{{Cite web|title=Bitbills|url=http://www.bitbills.com/|publisher=Bitbills|accessdate=29 September 2012}}</ref>

==History==
:Main article: [[History]]

A cryptographic system for untraceable payments was first described by David Chaum in 1982.<ref>[http://blog.koehntopp.de/uploads/Chaum.BlindSigForPayment.1982.PDF David Chaum, Blind signatures for untraceable payments], Advances in Cryptology - Crypto '82, Springer-Verlag (1983), 199–203.</ref> In 1990 Chaum extended this system to create the first cryptographic anonymous electronic cash system.,<ref>{{cite journal|journal=Lecture Notes in Computer Science|last1=Chaum|first1=David|last2=Fiat|first2=Amos|last3=Naor|first3=Moni|title=Untraceable Electronic Cash|url=http://blog.koehntopp.de/uploads/chaum_fiat_naor_ecash.pdf}}</ref> which became known as ecash.
<ref>{{cite web|url=http://www.wired.com/wired/archive/2.12/emoney.html|publisher=Wired|title=E-Money (That's What I Want)|date=1994–2012|author=Steven Levy}}</ref> In 1998 Wei Dai published a description of an anonymous, distributed electronic cash system which he called "b-money".<ref>{{cite web|title=B-Money|url=http://www.weidai.com/bmoney.txt|author=Wei Dai|year=1998}}</ref> Around the same time, Nick Szabo created ''bit gold''.<ref>{{cite web|url=http://spectrum.ieee.org/computing/software/bitcoin-the-cryptoanarchists-answer-to-cash/0|title=Bitcoin: The Cryptoanarchists’ Answer to Cash|publisher=IEEE Spectrum|quote=Around the same time, Nick Szabo, a computer scientist who now blogs about law and the history of money, was one of the first to imagine a new digital currency from the ground up. Although many consider his scheme, which he calls “bit gold,” to be a precursor to Bitcoin}}</ref><ref name="bitgold">{{cite web|title=Bit gold|url=http://unenumerated.blogspot.co.uk/2005/12/bit-gold.html|author=Nick Szabo|quote=My proposal for bit gold is based on computing a string of bits from a string of challenge bits, using functions called variously "client puzzle function," "proof of work function," or "secure benchmark function.". The resulting string of bits is the proof of work.... The last-created string of bit gold provides the challenge bits for the next-created string.}}</ref> Like Bitcoin, ''Bit gold'' was a currency system where users would compete to solve a [[proof of work]] function, with solutions being cryptographically chained together and published via a distributed property title registry. A variant of ''Bit gold'', called ''Reusable Proofs of Work'', was implemented by Hal Finney.<ref name="bitgold"/>

In 2008, Satoshi Nakamoto published a paper<ref name="whitepaper">{{cite web
|last= Nakamoto
|first= Satoshi
|title= Bitcoin: A Peer-to-Peer Electronic Cash System
|url= http://www.cs.kent.edu/~JAVED/class-P2P12F/papers-2012/PAPER2012-p2p-bitcoin-satoshinakamoto.pdf
|accessdate = 14 December 2010
|date= 24 May 2009
|postscript=
}}</ref><ref>{{cite web
|url= http://article.gmane.org/gmane.comp.encryption.general/12588/
|title= Bitcoin P2P e-cash paper
}}</ref> on The Cryptography Mailing list at metzdowd.com<ref>[http://www.mail-archive.com/search?l=cryptography@metzdowd.com&q=from:%22Satoshi+Nakamoto%22 Satoshi's posts to Cryptography mailing list]</ref> describing the Bitcoin protocol.

The Bitcoin network came into existence on 3 January 2009 with the release of the first Bitcoin client, [[wxBitcoin]], and the issuance of the first Bitcoins.<ref>{{cite web |title=Block 0 – Bitcoin Block Explorer |url=http://blockexplorer.com/block/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f }}</ref><ref>{{cite web |url=http://www.mail-archive.com/cryptography@metzdowd.com/msg10142.html |title=Bitcoin v0.1 released}}</ref><ref>{{cite web |url=http://sourceforge.net/news/?group_id=244765 |title=SourceForge.net: Bitcoin}}</ref>
A year after, the initial exchange rates for Bitcoin were set by individuals on the bitcointalk forums.{{Citation needed|date=October 2012}} The most significant transaction involved a 10,000 BTC pizza.<ref>{{cite web|title=The Rise and Fall of Bitcoin|url=http://www.wired.com/magazine/2011/11/mf_bitcoin/|publisher=Wired|accessdate=13 October 2012}}</ref>
Today, the majority of Bitcoin exchanges occur on the [[MtGox]] Bitcoin exchange.

In 2011, Wikileaks,<ref>{{cite news
|last= Greenberg
|first= Andy
|url= http://blogs.forbes.com/andygreenberg/2011/06/14/wikileaks-asks-for-anonymous-bitcoin-donations/
|title= WikiLeaks Asks For Anonymous Bitcoin Donations – Andy Greenberg – The Firewall – Forbes
|publisher= Blogs.forbes.com
|date= 2011-06-14
|accessdate = 2011-06-22
}}</ref> [[Freenet]],<ref>{{cite web
|url= https://freenetproject.org/donate.html
|title= /donate
|publisher= The Freenet Project
|date=
|accessdate = 2011-06-22
}}</ref> Singularity Institute,<ref>[http://singinst.org/donate/ SIAI donation page]</ref> Internet Archive,<ref>[http://www.archive.org/donate/index.php Internet Archive donation page]</ref> Free Software Foundation<ref>[https://my.fsf.org/donate/other/ Other ways to donate]</ref> and others, began to accept donations in Bitcoin. The Electronic Frontier Foundation did so for a while but has since stopped, citing concerns about a lack of legal precedent about new currency systems, and because they "generally don't endorse any type of product or service."<ref>{{cite web
|url= https://www.eff.org/deeplinks/2011/06/eff-and-bitcoin
|title= EFF and Bitcoin | Electronic Frontier Foundation
|publisher= Eff.org
|date= 2011-06-14
|accessdate = 2011-06-22
}}</ref> Some small businesses had started to adopt Bitcoin. LaCie, a public company, accepts Bitcoin for its Wuala service.<ref>{{Cite web|url=http://www.wuala.com/en/bitcoin |title=Secure Online Storage – Backup. Sync. Share. Access Everywhere |publisher=Wuala |date= |accessdate = 2012-01-24}}</ref>

In 2012, BitPay reports of having over 1000 merchants accepting Bitcoin under its payment processing service.<ref>{{cite web|title=BitPay Signs 1,000 Merchants to Accept Bitcoin Payments|url=http://www.americanbanker.com/issues/177_176/bitpay-signs-1000-merchants-to-accept-bitcoin-payments-1052538-1.html|publisher=American Banker|accessdate=12 October 2012}}</ref>

==Administration==
Bitcoin is administered through a decentralized peer-to-peer network.<ref name="whitepaper"/> Cryptographic technologies and the peer-to-peer network of computing power enables users to make and verify irreversible, instant online Bitcoin payments, without an obligation to trust and use centralized banking institutions and authorities. Dispute resolution services are not made directly available. Instead it is left to the users to verify and trust the parties they are sending money to through their choice of methods.

Bitcoins are issued according to rules agreed to by the majority of the computing power within the Bitcoin network. The core rules describing the predictable issuance of Bitcoins to its verifying servers, a voluntary and competitive transaction fee system and the hard limit of no more than 21 million BTC issued in total.<ref name="whitepaper"/>

Bitcoin does not require a central bank, State,<ref>{{cite web
|url= http://spectrum.ieee.org/computing/software/bitcoin-the-cryptoanarchists-answer-to-cash/3
|title= Bitcoin: The Cryptoanarchists' Answer to Cash
|publisher= IEEE.org
|date= June 2012
|accessdate = 2012-06-05
}}</ref> or incorporated backers.

==Services==
:Main article: [[Wallet]]

Bitcoins are sent and received through software and websites called wallets. They send and confirm transactions to the network through Bitcoin addresses, the identifiers for users' Bitcoin wallets within the network.<ref name="whitepaper"/>

===Bitcoin addresses===
:Main article: [[Address]]

Payments are made to Bitcoin "addresses": human-readable strings of numbers and letters around 33 characters in length, always beginning with the digit 1 or 3, as in the example of ''31uEbMgunupShBVTewXjtqbBv5MndwfXhb''.

Users obtain new Bitcoin addresses from their Bitcoin software. Creating a new address can be a completely offline process and require no communication with the Bitcoin network.

===Transaction fees===
:Main article: [[Transaction fees]]
Transaction fees may be included with any transfer of Bitcoins. {{As of|2012}} many transactions are processed in a way which makes no charge for the transaction. For transactions which consume or produce many coins (and therefore have a large data size), a small transaction fee is usually expected.

===Confirmations===
:Main article: [[Confirmation]]

The network's software confirms a transaction when it records it in a block. Further blocks of transactions confirm it even further. After six confirmations/blocks, a transaction is confirmed beyond reasonable doubt.

The network must store the whole transaction history inside the blockchain, which grows constantly as new records are added and never removed. Nakamoto conceived that as the database became larger, users would desire applications for Bitcoin that didn't store the entire database on their computer. To enable this, the blockchain uses a [[merkle tree]] to organize the transaction records in such a way that client software can locally delete portions of its own database it knows it will never need, such as earlier transaction records of Bitcoins that have changed ownership multiple times.

==Economics==

===Initial distribution===

Bitcoin has no centralized issuing authority.<ref name="ars-06-08-11">
{{Cite news
|first= Thomas
|last= Lowenthal
|title= Bitcoin: inside the encrypted, peer-to-peer digital currency
|newspaper= Ars Technica
|date= 8 June 2011
|url= http://arstechnica.com/tech-policy/news/2011/06/bitcoin-inside-the-encrypted-peer-to-peer-currency.ars
}}</ref><ref>{{cite news
|author= Sponsored by
|url= http://www.economist.com/blogs/babbage/2011/06/virtual-currency
|title= Virtual currency: Bits and bob
|publisher= The Economist
|date=
|accessdate = 2011-06-22
}}</ref><ref>{{cite web
|last= Geere
|first= Duncan
|url= http://www.wired.co.uk/news/archive/2011-05/16/bitcoin-p2p-currency
|title= Peer-to-peer currency Bitcoin sidesteps financial institutions (Wired UK)
|publisher= Wired.co.uk
|date=
|accessdate = 2011-06-22
}}</ref> The network is programmed to increase the money supply as a geometric series until the total number of Bitcoins reaches 21 million BTC.<ref name="Quantitative Analysis of the Full Bitcoin Transaction Graph"/> {{As of|2012|10}} slightly over 10 million of the total 21 million BTC had been created; the current total number created is available online.<ref>{{cite web
|title= Total Number of Bitcoins in Existence
|url= http://blockexplorer.com/q/totalbc
|work= Bitcoin Block Explorer
|accessdate = 2012-10-03
}}</ref> By 2013 half of the total supply will have been generated, and by 2017, three-quarters will have been generated. To ensure sufficient granularity of the [[money supply]], clients can divide each BTC unit down to eight decimal places (a total of 2.1 × 1015 or 2.1 quadrillion units).<ref name="lwn">{{Cite news
|author= Nathan Willis
|date= 2010-11-10
|title= Bitcoin: Virtual money created by CPU cycles
|publisher= LWN.net
|url= http://lwn.net/Articles/414452/
}}</ref>

The network {{As of|2012|lc=on}} required over one million times more work for confirming a block and receiving an award (25 BTC {{As of|2012|2|lc=on}}) than when the first blocks were confirmed.
The difficulty is automatically adjusted every 2016 blocks based on the time taken to find the previous 2016 blocks such that one block is created roughly every 10 minutes.

Those who chose to put computational and electrical resources toward mining early on had a greater chance at receiving awards for block generations. This served to make available enough processing power to process blocks. Indeed, without miners there are no transactions and the Bitcoin economy comes to a halt.

===Exchange rate===
Prices fluctuate relative to goods and services more than more widely accepted currencies;
the price of a Bitcoin is not static.

In August 2012, 1 BTC traded at around $10.00 USD. Taking into account the total number of Bitcoins mined, the monetary base of the Bitcoin network stands at over 110 million USD.<ref>[http://www.bitcoinwatch.com/ http://www.bitcoinwatch.com/] Bitcoin statistics</ref>

== Security ==
:Main article: [[Weaknesses]]

In the history of bitcoin, there have been a few [[incidents]], caused by problematic as well as malicious transactions. In the worst such incident, and the only one of its type, a person was able to pretend that he had a practically infinite supply of bitcoins, for almost 9 hours.

Bitcoin relies, among other things, on [http://en.wikipedia.org/wiki/Public-key_cryptography public key cryptography] and thus may be vulnerable to [http://en.wikipedia.org/wiki/Elliptic_curve_cryptography#Quantum_computing_attacks quantum computing attacks] if and when practical quantum computers can be constructed.

If multiple different software packages, whose usage becomes widespread on the Bitcoin network, disagree on the protocol and the rules for transactions, this could potentially cause a fork in the block chain, with each faction of users being able to accept only their own version of the history of transactions. This could influence the price of bitcoins.

A global, organized campaign against the currency or the software could also influence the demand for bitcoins, and thus the exchange price.

==Bitcoin mining==
:Main article: [[Mining]]

Bitcoin mining nodes are responsible for managing the Bitcoin network.

Bitcoins are awarded to Bitcoin nodes known as "miners" for the solution to a difficult [[proof-of-work]] problem which confirms transactions and prevents double-spending. This incentive, as the Nakamoto white paper describes it, encourages "nodes to support the network, and provides a way to initially distribute coins into circulation, since no central authority issues them."<ref name="whitepaper" />

Nakamoto compared the generation of new coins by expending CPU time and electricity to gold miners expending resources to add gold to circulation.<ref name="whitepaper"/>

===Node operation===

The node software for the Bitcoin network is based on peer-to-peer networking, digital signatures and cryptographic proof to make and verify transactions. Nodes broadcast transactions to the network, which records them in a public record of all transactions, called the ''blockchain'', after validating them with a [[proof-of-work|proof-of-work system]].

Satoshi Nakamoto designed the first Bitcoin node and mining software<ref name="processors">{{Cite news
|last= Davis
|first= Joshua
|title= The Crypto-Currency
|url= http://www.wired.com/magazine/2011/11/mf_bitcoin/all
|accessdate = 11 November 2011
|newspaper= Wired Magazine
|date= 10 November 2011
}}</ref> and developed the majority of the first implementation, Bitcoind, from 2007 to mid-2010.<ref name="code_start">{{cite web
|url= https://bitcointalk.org/index.php?topic=13.msg46#msg46
|title= Questions about Bitcoin
|publisher= Bitcoin forum
|date= 2009-12-10
}}</ref>

Node implementations include core software such as Bitcoind/Bitcoin-Qt, [[libbitcoin]], [[cbitcoin]]<ref>{{Cite web|title=cbitcoin|url=https://github.com/MatthewLM/cbitcoin|accessdate=3 October 2012}}</ref> and BitCoinJ.<ref>{{cite web
|url= http://news.slashdot.org/story/11/03/23/0210207/Google-Engineer-Releases-Open-Source-Bitcoin-Client
|title= Google Engineer Releases Open Source Bitcoin Client
|author= angry tapir, timothy
|date= 23 March 2011
|publisher= Slashdot
|accessdate = 2011-05-18
}}</ref><ref>{{cite web
|url= http://www.javaworld.com/javaworld/jw-01-2012/120110-bitcoin-for-beginners-3.html?page=1
|title= Bitcoin for beginners: The BitcoinJ API
|author= Dirk Merkel
|date= 10 January 2012
|publisher= JavaWorld
|accessdate = 2012-08-03
}}</ref>

Every node in the Bitcoin network collects all the unacknowledged transactions it knows of in a file called a ''block'', which also contains a reference to the previous valid block known to that node. It then appends a [[nonce]] value to this previous block and computes the SHA-256 cryptographic hash of the block and the appended nonce value. The node repeats this process until it adds a nonce that allows for the generation of a hash with a value lower than a specified ''target''. Because computers cannot practically reverse the hash function, finding such a nonce is hard and requires on average a predictable amount of repetitious trial and error. This is where the ''[[proof-of-work]]'' concept comes in to play. When a node finds such a solution, it announces it to the rest of the network. Peers receiving the new solved block validate it by computing the hash and checking that it really starts with the given number of zero bits (i.e., that the hash is within the target). Then they accept it and add it to the chain.

===Mining rewards===
In addition to receiving the pending transactions confirmed in the block, a generating node adds a ''generate'' transaction, which awards new Bitcoins to the operator of the node that generated the block. The system sets the payout of this generated transaction according to its defined inflation schedule. The miner that generates a block also receives the fees that users have paid as an incentive to give particular transactions priority for faster confirmation.

The network never creates more than a 50 BTC reward per block and this amount will decrease over time towards zero, such that no more than 21 million BTC will ever exist.<ref name="lwn" /> As this payout decreases, the incentive for users to run block-generating nodes is intended to change to earning [[#Transaction fees|transaction fees]].

===Mining pools===
:Main article: [[Pooled mining]]

Bitcoin users often pool computational effort to increase the stability of the collected fees and subsidy they receive.<ref name="We Use Coins Mining">{{cite web|title=About Bitcoin Mining|url=http://www.weusecoins.com/mining-guide.php|publisher=We Use Coins|accessdate=18 October 2012}}</ref>

===Mining difficulty===
:Main article: [[Difficulty]]

In order to throttle the creation of blocks, the difficulty of generating new blocks is adjusted over time. If mining output increases or decreases, the difficulty increases or decreases accordingly.

The adjustment is done by changing the threshold that a hash is required to be less than. A lower threshold means fewer possible hashes can be accepted, and thus a higher degree of difficulty. The target rate of block generation is one block every 10 minutes, or 2016 blocks every two weeks. Bitcoin changes the difficulty of finding a valid block every 2016 blocks, using the difficulty that would have been most likely to cause the prior 2016 blocks to have taken two weeks to generate, according to the timestamps on the blocks. Technically, this is done by modeling the generation of Bitcoins as Poisson process. All nodes perform and enforce the same difficulty calculation.

Difficulty is intended as an automatic stabilizer allowing mining for Bitcoins to remain profitable in the long run for the most efficient miners, independently of the fluctuations in demand of Bitcoin in relation to other currencies.

===Mining hardware===
:Main article: [[Mining Hardware Comparison]]

Bitcoins used to be mined through Intel/AMD CPUs. {{As of | 2012}}, mining has gradually moved to [[GPU]] and [[FPGA]] hardware.<ref name="bitcoinmag-butterfly" /> [[Application-specific integrated circuit|ASIC]]-based hardware for Bitcoin mining has been announced by several manufacturers who intend to ship products from late 2012 to early 2013.<ref name="bitcoinmag-butterfly">{{Cite web|title=Bitpay Breaks Daily Volume Record with Butterfly ASIC mining release|url=http://bitcoinmagazine.net/bitpay-breaks-daily-volume-record-with-butterfly-asic-mining-release/|publisher=Bitcoin Magazine}}</ref>

==Concerns==

===As an investment===
Bitcoin describes itself as an experimental digital currency. Reuben Grinberg has noted that Bitcoin's supporters have argued that Bitcoin is neither a security or an investment because it fails to meet the criteria for either category.<ref name="grinberg">{{cite web | url=http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1817857 | title=Bitcoin: An Innovative Alternative Digital Currency | publisher=SSRN | date=9 December 2011 | accessdate=4 December 2012 | author=Grinberg, Reuben}}</ref> Although it is a virtual currency, some people see it as an investment<ref name="cnbc">{{cite web | url=http://www.cnbc.com/id/45030812/The_Pros_And_Cons_Of_Biting_on_Bitcoins | title=The Pros And Cons Of Biting on Bitcoins | publisher=CNBC | date=23 November 2011 | accessdate=4 December 2012 | author=Gustke, Constance}}</ref> or accuse it of being a form of investment fraud known as a Ponzi scheme.<ref>{{cite web |url=http://www.theregister.co.uk/2011/06/08/bitcoin_under_attack/ |title=US senators draw a bead on Bitcoin |last1=Chirgwin |first1=Richard |date=8 June 2011 |publisher=The Register |accessdate=14 November 2012}}</ref><ref>{{cite web |url=http://uk.reuters.com/article/2012/04/01/uk-traders-bitcoin-idUKBRE8300JL20120401 |title=Bitcoin, the City traders' anarchic new toy |last1=O'Leary |first1=Naomi |date=2 April 2012 |publisher=Reuters |accessdate=14 November 2012}}</ref> A report by the European Central Bank, using the U.S. Securities and Exchange Commission's definition of a Ponzi scheme, found that the use of bitcoins shares some characteristics with Ponzi schemes, but also has characteristics of its own which contradict several common aspects of Ponzi schemes.<ref name="ecbreport">{{cite web | url=http://www.ecb.europa.eu/pub/pdf/other/virtualcurrencyschemes201210en.pdf | title=Virtual Currency Schemes | publisher=European Central Bank | date=October 2012 | accessdate=4 December 2012}}</ref>

===Privacy===
Because transactions are broadcast to the entire network, they are inherently public. Unlike regular banking,<ref>{{cite web
|url= http://spectrum.ieee.org/computing/software/bitcoin-the-cryptoanarchists-answer-to-cash/0
|title= Bitcoin: The Cryptoanarchists' Answer to Cash
|publisher= IEEE.org
|date= June 2012
|accessdate = 2012-06-05
}}</ref> which preserves customer privacy by keeping transaction records private, loose transactional privacy is accomplished in Bitcoin by using many unique addresses for every wallet, while at the same time publishing all transactions. As an example, if Alice sends 123.45 BTC to Bob, the network creates a public record that allows anyone to see that 123.45 has been sent from one address to another. However, unless Alice or Bob make their ownership of these addresses known, it is difficult for anyone else to connect the transaction with them. However, if someone connects an address to a user at any point they could follow back a series of transactions as each participant likely knows who paid them and may disclose that information on request or under duress.

It can be difficult to associate Bitcoin identities with real-life identities.<ref name="An Analysis of Anonymity in the Bitcoin System">Fergal Reid and Martin Harrigan (24 July 2011). [http://anonymity-in-bitcoin.blogspot.com/2011/07/bitcoin-is-not-anonymous.html An Analysis of Anonymity in the Bitcoin System]. An Analysis of Anonymity in the Bitcoin System.</ref> This property makes Bitcoin transactions attractive to sellers of illegal products.<ref name="Forbes">Andy Greenberg (20 April 2011). [http://www.forbes.com/forbes/2011/0509/technology-psilocybin-bitcoins-gavin-andresen-crypto-currency.html Crypto Currency]. Forbes Magazine.</ref><ref>{{cite web
|last= Madrigal
|first= Alexis
|title= Libertarian Dream? A Site Where You Buy Drugs With Digital Dollars
|publisher= The Atlantic Monthly
|date= 2011-06-01
|url= http://www.theatlantic.com/technology/archive/2011/06/libertarian-dream-a-site-where-you-buy-drugs-with-digital-dollars/239776/
|accessdate = 2011-06-05
}}</ref>

===Illicit use===

====Cracking====
The cracking organization "LulzSec" accepted donations in Bitcoin, having said that the group "needs Bitcoin donations to continue their hacking efforts".<ref name="CNET">{{cite web
|last= Reisinger
|first= Don
|url= http://news.cnet.com/8301-13506_3-20070268-17/senators-target-bitcoin-currency-citing-drug-sales/
|title= Senators target Bitcoin currency, citing drug sales | The Digital Home – CNET News
|publisher= News.cnet.com
|date= 2011-06-09
|accessdate = 2011-06-22
}}</ref><ref>{{cite news
|last= Olson
|first= Parmy
|url= http://blogs.forbes.com/parmyolson/2011/06/06/lulzsec-hackers-posts-sony-dev-source-code-get-7k-donation/
|title= LulzSec Hackers Post Sony Dev. Source Code, Get $7K Donation – Parmy Olson – Disruptors – Forbes
|publisher= Blogs.forbes.com
|date= 6 June 2011
|accessdate = 2011-06-22
}}</ref>

====Silk Road====
[[Silk Road]] is an anonymous black market that uses only the Bitcoin.<ref name="npr-06-12-11">
{{Cite news
|url= http://www.npr.org/2011/06/12/137138008/silk-road-not-your-fathers-amazon-com
|date= 12 June 2011
|newspaper= NPR
|title= Silk Road: Not Your Father's Amazon.com
|author= Staff
}}</ref>

In a 2011 letter to Attorney General Eric Holder and the Drug Enforcement Administration, senators Charles Schumer of New York and Joe Manchin of West Virginia called for an investigation into Silk Road and the Bitcoin.<ref name="npr-06-12-11"/>
Schumer described the use of Bitcoins at Silk Road as a form of money laundering.<ref name="ars-06-08-11"/>

====Botnet mining====
In June 2011, Symantec warned about the possibility of botnets engaging in covert "mining" of Bitcoins,<ref>{{Cite web|author=Updated: 17 June 2011 | Translations available: 日本語 |url=http://www.symantec.com/connect/blogs/bitcoin-botnet-mining |title=Bitcoin Botnet Mining | Symantec Connect Community |publisher=Symantec.com |date=2011-06-17 |accessdate = 2012-01-24}}</ref><ref>{{Cite web|url=http://www.zdnet.com/blog/security/researchers-find-malware-rigged-with-bitcoin-miner/8934 |title=Researchers find malware rigged with Bitcoin miner |publisher=ZDNet |date=2011-06-29 |accessdate = 2012-01-24}}</ref> consuming computing cycles, using extra electricity and possibly increasing the temperature of the computer. Later that month, the Australian Broadcasting Corporation caught an employee using the company's servers to generate Bitcoins without permission.<ref>{{Cite web|url=http://thenextweb.com/au/2011/06/23/abc-employee-caught-mining-for-bitcoins-on-company-servers/ |title=ABC employee caught mining for Bitcoins on company servers |publisher=The Next Web |date=2011-06-23 |accessdate = 2012-01-24}}</ref> Some malware also uses the parallel processing capabilities of the GPUs built into many modern-day video cards.<ref>{{Cite news |url=http://www.theregister.co.uk/2011/08/16/gpu_bitcoin_brute_forcing/ |title=Malware mints virtual currency using victim's GPU |date=16 August 2011|first=Dan |last=Goodin }}</ref> In mid August 2011, Bitcoin miner botnets were found;<ref>{{Cite web|url=http://www.infosecurity-magazine.com/view/20211/researcher-discovers-distributed-bitcoin-cracking-trojan-malware/ |title=Infosecurity – Researcher discovers distributed bitcoin cracking trojan malware |publisher=Infosecurity-magazine.com |date=2011-08-19 |accessdate = 2012-01-24}}</ref> trojans infecting Mac OS X have also been uncovered.<ref>{{Cite web|url=http://www.techworld.com.au/article/405849/mac_os_x_trojan_steals_processing_power_produce_bitcoins |title=Mac OS X Trojan steals processing power to produce Bitcoins – sophos, security, malware, Intego – Vulnerabilities – Security |publisher=Techworld |date=2011-11-01 |accessdate = 2012-01-24}}</ref>

===Theft and fraud===
On 19 June 2011, a security breach of the Mt.Gox (an acronym for ''M''agic: ''T''he ''G''athering ''O''nline E''x''change, its original purpose) Bitcoin Exchange caused the price of a Bitcoin to briefly drop to US$0.01 on the Mt.Gox exchange (though it remained unaffected on other exchanges) after a hacker allegedly used credentials from a Mt.Gox auditor's compromised computer to illegally transfer a large number of Bitcoins to him- or herself and sell them all, creating a massive "ask" order at any price. Within minutes the price rebounded to over $15 before Mt.Gox shut down their exchange and canceled all trades that happened during the hacking period.<ref>[https://mtgox.com/press_release_20110630.html Clarification of Mt Gox Compromised Accounts and Major Bitcoin Sell-Off]</ref><ref>[http://www.youtube.com/watch?v=T1X6qQt9ONg YouTube. Bitcoin Report]</ref> The exchange rate of Bitcoins quickly returned to near pre-crash values.<ref name="mick">Jason Mick, 19 June 2011, [http://www.dailytech.com/Inside+the+MegaHack+of+Bitcoin+the+Full+Story/article21942.htm Inside the Mega-Hack of Bitcoin: the Full Story], DailyTech</ref><ref>Timothy B. Lee, 19 June 2011, [http://arstechnica.com/tech-policy/news/2011/06/bitcoin-price-plummets-on-compromised-exchange.ars Bitcoin prices plummet on hacked exchange], Ars Technica</ref><ref>Mark Karpeles, 20 June 2011, [https://support.mtgox.com/entries/20208066-huge-bitcoin-sell-off-due-to-a-compromised-account-rollback Huge Bitcoin sell off due to a compromised account – rollback], Mt.Gox Support</ref><ref name="register1">{{Cite news
|title= Bitcoin collapses on malicious trade – Mt Gox scrambling to raise the Titanic
|url= http://www.theregister.co.uk/2011/06/19/bitcoin_values_collapse_again/
|date= 2011-06-19
|author= Chirgwin, Richard
|publisher= The Register
}}</ref> Accounts with the equivalent of more than USD 8,750,000 were affected.<ref name="mick" />

In July 2011, The operator of Bitomat, the third largest Bitcoin exchange, announced that he lost access to his wallet.dat file with about 17,000 BitCoins (roughly equivalent to 220,000 USD at that time). He announced that he would sell the service for the missing amount, aiming to use funds from the sale to refund his customers.<ref>[http://siliconangle.com/blog/2011/08/01/third-largest-bitcoin-exchange-bitomat-lost-their-wallet-over-17000-bitcoins-missing/ Third Largest Bitcoin Exchange Bitomat Lost Their Wallet, Over 17,000 Bitcoins Missing]. SiliconAngle</ref>

In August 2011, MyBitcoin, one of popular Bitcoin transaction processors, declared that it was hacked, which resulted in it being shut down, with paying 49% on customer deposits, leaving more than 78,000 BitCoins (roughly equivalent to 800,000 USD at that time) unaccounted for.<ref>[http://betabeat.com/2011/08/mybitcoin-spokesman-finally-comes-forward-what-did-you-think-we-did-after-the-hack-we-got-shitfaced/ MyBitcoin Spokesman Finally Comes Forward: “What Did You Think We Did After the Hack? We Got Shitfaced”]. BetaBeat</ref><ref>[http://betabeat.com/2011/08/search-for-owners-of-mybitcoin-loses-steam/ Search for Owners of MyBitcoin Loses Steam]. BetaBeat</ref>

In early August 2012, a lawsuit was filed in San Francisco court against Bitcoinica, claiming about 460,000 USD from the company. Bitcoinica was hacked twice in 2012, which led to allegations of neglecting the safety of customers' money and cheating them out of withdrawal requests.<ref>[http://arstechnica.com/tech-policy/2012/08/bitcoinica-users-sue-for-460k-in-lost-bitcoins/ Bitcoinica users sue for $460k in lost Bitcoins]. Arstechnica</ref><ref>[http://spectrum.ieee.org/tech-talk/computing/networks/first-bitcoin-lawsuit-filed-in-san-francisco First Bitcoin Lawsuit Filed In San Francisco]. IEEE Spectrum</ref>

In late August 2012, Bitcoin Savings and Trust was shut down by the owner, allegedly leaving around $5.6 million in debts; this led to allegations of the operation being a Ponzi scheme.<ref>{{Cite web|title=Bitcoin ponzi scheme – investors lose $5 million USD in online hedge fund|url=http://rt.com/usa/news/investors-currency-digital-fund-868/|publisher=RT}}</ref><ref>{{Cite web|last=Jeffries|first=Adrianne|title=Suspected multi-million dollar Bitcoin pyramid scheme shuts down, investors revolt|url=http://www.theverge.com/2012/8/27/3271637/bitcoin-savings-trust-pyramid-scheme-shuts-down|publisher=The Verge}}</ref><ref>{{Cite web|last=Mick|first=Jason|title="Pirateat40" Makes Off $5.6M USD in BitCoins From Pyramid Scheme|url=http://www.dailytech.com/Pirateat40+Makes+Off+56M+USD+in+BitCoins+From+Pyramid+Scheme/article25538.htm|publisher=DailyTech}}</ref><ref>[http://pandodaily.com/2012/08/31/bitcoin-how-a-virtual-currency-became-real-with-a-5-6m-fraud/ Bitcoin: How a Virtual Currency Became Real with a $5.6M Fraud]. PandoDaily</ref> In September 2012, it was reported that U.S. Securities and Exchange Commission has started an investigation on the case.<ref>[http://blogs.telegraph.co.uk/technology/willardfoxton2/100007836/bitcoin-pirate-scandal-sec-steps-in-amid-allegations-that-the-whole-thing-was-a-ponzi-scheme/ Bitcoin 'Pirate' scandal: SEC steps in amid allegations that the whole thing was a Ponzi scheme ]. The Telegraph</ref>

In September 2012, Bitfloor Bitcoin exchange also reported being hacked, with 24,000 BitCoins (roughly equivalent to 250,000 USD) stolen. As a result, Bitfloor suspended operations.<ref>[http://www.bbc.co.uk/news/technology-19486695 Bitcoin theft causes Bitfloor exchange to go offline]. BBC</ref><ref>[http://www.theverge.com/2012/9/5/3293375/bitfloor-bitcoin-exchange-suspended-theft Bitcoin exchange BitFloor suspends operations after $250,000 theft Bitcoin exchange BitFloor suspends operations after $250,000 theft]. The Verge</ref> The same month, Bitfloor resumed operations, with its founder saying that he reported the theft to FBI, and that he is planning to repay the victims, though the time frame for such repayment is unclear.<ref>[http://www.pcworld.com/article/2010586/bitcoin-exchange-back-online-after-hack.html?tk=rel_news Bitcoin exchange back online after hack]. PCWorld</ref>

===Taxation===
In September 2012, the Intra-European Organization of Tax Administrations (IOTA), in Tbilisi, Georgia, held a workshop titled "Auditing Individuals and Legal Entities in the Use of e-Money." The workshop was attended by representatives from 23 countries.<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref> Jerry Taylor, IOTA's technical taxation expert, said, "There's an awful lot happening on the Internet environment which is fascinating at the moment and introducing new challenges for auditors when it comes to virtual currency."<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref> Bitcoin was mentioned during the workshop.<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref>

Matthew Elias, founder of the [[Cryptocurrency Legal Advocacy Group]] (CLAG) published "Staying Between the Lines: A Survey of U.S. Income Taxation and its Ramifications on Cryptocurrencies", which discusses "the taxability of cryptocurrencies such as bitcoin."<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref> CLAG "stressed the importance for taxpayers to determine on their own whether taxes are due on a bitcoin-related transaction based on whether one has "experienced a realization event."<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref> Such examples are "when a taxpayer has provided a service in exchange for bitcoins, a realization event has probably occurred, and any gain or loss would likely be calculated using fair market values for the service provided."<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref>

[[Peter Vessenes]], [[Bitcoin Foundation|Bitcoin Foundation's]] executive director, said, since the foundation is trying to pay for everything in bitcoin, including salaries, "How do we W-2 someone for their bitcoins? Do we mark-to-market every time a transfer happens? Payroll companies cringe."<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref> The Bitcoin Foundation hopes "to push for solid guidance about its legal and tax treatment." [[Patrick Murck]], legal counsel for the Bitcoin Foundation, said he would like "to help regulators understand the technology better so they can make better decisions."<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref> Murck said, "Bitcoin has the potential to become much more than a niche currency, but it needs the guidance and understanding of regulators." and "The full potential of bitcoin could be realized through clearer guidelines and a better understanding by financial and tax regulators." and "Part of making that happen is to talk to regulators, the IRS, and tax professionals and helping them understand that bitcoin is not this nefarious thing, it's just software, it's a community, and there's nothing inherently nefarious about either of those things."<ref name="BitCoin Tax issues Oct 2012">{{cite journal | title=2012 TNT 209-4 NEWS ANALYSIS: VIRTUAL CURRENCY: A NEW WORRY FOR TAX ADMINISTRATORS?. (Release Date: OCTOBER 17, 2012) (Doc 2012-21516) | author=Stewart, David D. and Soong Johnston, Stephanie D. | journal=Tax Notes Today | year=2012 | month=October 29 | volume=2012 TNT 209-4 | issue=2012 TNT 209-4}}</ref>

==See Also==
* [[Introduction]]
* [[Getting started]]
* [[Using_Bitcoin|Detailed tutorial]]
* [[FAQ]]

==References==
<references />

[[Category:Digital currencies]]

How bitcoin works

2013-03-08T19:47:35Z

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<center>
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This page explains the basic framework of Bitcoin's functionality.

==Cryptography==

There are several cryptographic technologies that make up the essence of Bitcoin.

First is [http://en.wikipedia.org/wiki/Public-key_cryptography public key cryptography]. Each coin is associated with its current owner's public [http://en.wikipedia.org/wiki/Elliptic_Curve_DSA ECDSA] key. When you send some bitcoins to someone, you create a message ([[transaction]]), attaching the new owner's public key to this amount of coins, and sign it with your private key. When this transaction is broadcast to the bitcoin network, this lets everyone know that the new owner of these coins is the owner of the new key. Your signature on the message verifies for everyone that the message is authentic. The complete history of transactions is kept by everyone, so anyone can verify who is the current owner of any particular group of coins.

This complete record of transactions is kept in the [[block chain]], which is a sequence of records called [[block|blocks]]. All computers in the network have a copy of the block chain, which they keep updated by passing along new blocks to each other. Each block contains a group of transactions that have been sent since the previous block. In order to preserve the integrity of the block chain, each block in the chain confirms the integrity of the previous one, all the way back to the first one, the [[genesis block]]. Record insertion is costly because each block must meet certain requirements that make it [[difficulty|difficult]] to generate a valid block. This way, no party can overwrite previous records by just forking the chain.

To make generating bitcoins difficult the [http://en.wikipedia.org/wiki/Hashcash Hashcash] cost-function is used. Hashcash is the first secure efficiently verifiable cost-function or proof-of-work function. The beauty of hashcash is that is is non-interactive and has no secret keys that have to be managed by a central server or relying party; hashcash is as a result fully distributed and infinitely scalable. (Hashcash uses symmetric key cryptogaphy, namely a one-way hashcash function - typically either SHA1 or SHA-256).

In bitcoin, integrity, block-chaining, and the hashcash cost-function all use [http://en.wikipedia.org/wiki/SHA-2 SHA256] as the underlying [http://en.wikipedia.org/wiki/Cryptographic_hash_function cryptographic hash function].

A cryptographic hash function essentially takes input data which can be of practically any size, and transforms it, in an effectively-impossible to reverse or to predict way, into a relatively compact string (in the case of SHA-256 the hash is 32 bytes). Making the slightest change to the input data changes its hash unpredictably, so nobody can create a different block of data that gives exactly the same hash. Therefore, by being given a compact hash, you can confirm that it matches only a particular input datum, and in bitcoin the input data being a block-chain is significantly larger than the SHA-256 hash. This way, Bitcoin blocks don't have to contain serial numbers, as blocks can be identified by their hash, which serves the dual purpose of identification as well as integrity verification. An identification string that also provides its own integrity is called a self-certifying identifier.

The hashcash [[difficulty]] factor is achieved by requiring that the hash output has a number of leading zeros. Technically, to allow more fine-grained control than Hashcash number of leading 0-bits method, Bitcoin extends the hashcash solution definition by treating the hash as a large big-endian integer, and checking that the integer is below a certain threshold. The hashcash cost-function iterates by perturbing data in the block by a [[nonce]] value, until the data in the block hashes to produce an integer below the threshold - which takes a lot of processing power. This low hash value for the block serves as an easily-verifiable [[proof of work]] - every node on the network can instantly verify that the block meets the required criteria.

With this framework, we are able to achieve the essential functions of the Bitcoin system. We have verifiable ownership of bitcoins, and a distributed database of all transactions, which prevents [[#Double_spending|double spending]].

==Bitcoin [[Mining]]==

We have mentioned in the previous section that adding a block to the block chain is difficult, requiring time and processing power to accomplish. The incentive to put forth this time and electricity is that the person who manages to produce a block gets a reward. This reward is two-fold. First, the block producer gets a bounty of some number of bitcoins, which is agreed-upon by the network. (Currently this bounty is 25 bitcoins; this value will halve every 210,000 blocks.) Second, any [[transaction fees]] that may be present in the transactions included in the block, get claimed by the block producer.

This gives rise to the activity known as "Bitcoin [[Mining|mining]]" - using processing power to try to produce a valid block, and as a result 'mine' some bitcoins. The network rules are such that the [[difficulty]] is adjusted to keep block production to approximately 1 block per 10 minutes. Thus, the more miners engage in the mining activity, the more difficult it becomes for each individual miner to produce a block. The higher the total difficulty, the harder it is for an attacker to overwrite the tip of the block chain with his own blocks (which enables him to double-spend his coins. See the [[weaknesses]] page for more details).

Besides being important for maintaining the transaction database, mining is also the mechanism by which bitcoins get created and distributed among the people in the bitcoin economy. The network rules are such that over the next hundred years, give or take a few decades, a total of 21 million bitcoins will be created. See [[Controlled Currency Supply]]. Rather than dropping money out of a helicopter, the bitcoins are awarded to those who contribute to the network by creating [[block]]s in the [[block chain]].

==Double spending==

The [[block chain]] is a common ledger shared by all Bitcoin nodes which details the owner of each bitcoin, or fraction thereof. Unlike conventional banking systems, there is no central place where this ledger of transactions is stored. This is accomplished through the broadcasting of small pieces ("blocks"), each stating that it is a continuation of a previous block. It is possible for the block chain to split; that is, it is possible for two blocks to both point to the same parent block and contain some, but not all, of the same transactions. When this happens, each computer in the network must decide for itself which branch is the "correct" one that should be accepted and extended further.

The rule in this case is to accept the "longest" valid branch. Choose from the branches of blocks that you have received, the path, the total "difficulty" of which is the highest. This is the sequence of blocks that is assumed to have required the most work (CPU time) to generate. For Bitcoin, this will be the "true" order of events, and this is what it will take into account when calculating the balance to show to the user.

It is still possible that, as new blocks are constantly being generated, at some later time, some other branch will become the longest branch. However, it takes significant effort to extend a branch, and nodes work to extend the branch that they have received and accepted (which is normally the longest one). So, the longer this branch becomes compared to the second-longest branch, the more effort it will take for the second-longest branch to catch up and overcome the first in length. Also, the more nodes in the network hear about the longest branch, the more unlikely it becomes for other branches to be extended the next time a block is generated, since the nodes will accept the longest chain.

Therefore, the more time a transaction has been part of the longest block chain, the more likely it is to remain part of the chain indefinitely. This is what makes transactions non-reversible and this is what prevents people from [[double-spending]] their coins. What the receiver of each transaction does, after money has been supposedly transferred to him/her is to check how long the block chain following the said transaction has become, because the more blocks are added to the longest branch after the transaction, the less likely is it that some other branch will overcome it.

When the block chain after the transaction has become long enough, it becomes near-impossible for another branch to overcome it, and so people can start accepting the transaction as true. This is why 'blocks' also serve as 'confirmations' for a transaction. Even if another branch does overcome the one with the transaction, most of the blocks will have been generated by people who have no affiliation with the sender of the coins, as a large number of people are working to generate blocks. Since transactions are broadcasted to all nodes in the network, these blocks are just as likely to contain the transaction as the blocks in the previously-accepted branch.

Bitcoin relies on the fact that no single entity can control most of the CPU power on the network for any significant length of time, since, if they could, they would be able to extend any branch of the tree they chose, and faster than any other branch can be extended, making it the longest branch, and then permanently controlling which transactions appear in it.

==See also==

* [[Introduction]]
* [[Getting started]]
* [[Using Bitcoin]]
* Bitcoin [[FAQ]]
* [[Double-spending]]

==External Links==

* http://bitcointalk.org/index.php?topic=2487.0 A forum thread with some good 'for-the-layperson' explanations of how bitcoin works.

[[Category:Introduction]]

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Proof of work

2013-03-08T19:38:16Z

Atheros: I don't see why this is a stub. There are no empty categories for more information.

A '''proof of work''' is a piece of data which was difficult (costly, time-consuming) to produce so as to satisfy certain requirements. It must be trivial to check whether data satisfies said requirements. Producing a proof of work can be a random process with low probability, so that a lot of trial and error is required ''on average'' before a valid proof of work is generated.

One application of this idea is a proposed [http://en.wikipedia.org/wiki/Hashcash method for preventing email spam], requiring a proof of work on the email's contents (including the To address), on every email. Legitimate emails will be able to do the work to generate the proof easily (not much work is required for a single email), but mass spam emailers will have difficulty generating the required proofs (which would require huge computational resources).

Proofs of work are used in Bitcoin for block generation. Proofs of work that are tied to the data of each block are required for the blocks to be accepted. The [[difficulty]] of this work is adjusted so as to limit the rate at which new blocks can be generated by the network to one every 10 minutes. Due to the very low probability of successful generation, this makes it unpredictable which worker computer in the network will be able to generate the next block.

For a block to be valid it must hash to a value less than the current [[target]]; this means that each block indicates that work has been done generating it. Each block contains the hash of the preceding block, thus each block has a [[block chain|chain]] of blocks that together contain a large amount of work. Changing a block (which can only be done by making a new block containing the same predecessor) requires regenerating all successors and redoing the work they contain. This protects the block chain from tampering.

== Example ==

Let's say the base string that we are going to do work on is "Hello, world!". Our target is to find a variation of it that SHA-256 hashes to a value beginning with '000'. We vary the string by adding an integer value to the end called a [[nonce]] and incrementing it each time. Finding a match for "Hello, world!" takes us 4251 tries (but happens to have zeroes in the first four digits):

"Hello, world!0" => 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64
"Hello, world!1" => e9afc424b79e4f6ab42d99c81156d3a17228d6e1eef4139be78e948a9332a7d8
"Hello, world!2" => ae37343a357a8297591625e7134cbea22f5928be8ca2a32aa475cf05fd4266b7
...
"Hello, world!4248" => 6e110d98b388e77e9c6f042ac6b497cec46660deef75a55ebc7cfdf65cc0b965
"Hello, world!4249" => c004190b822f1669cac8dc37e761cb73652e7832fb814565702245cf26ebb9e6
"Hello, world!4250" => 0000c3af42fc31103f1fdc0151fa747ff87349a4714df7cc52ea464e12dcd4e9

4251 hashes on a modern computer is not very much work (most computers can achieve at least 4 million hashes per second). Bitcoin automatically varies the [[difficulty]] (and thus the amount of work required to generate a block) to keep a roughly constant rate of block generation. The probability of a single hash succeeding can be found [http://blockexplorer.com/q/probability here].

In Bitcoin things are a bit more complex, especially since the header contains the [http://en.wikipedia.org/wiki/Merkle_tree Merkle tree] which depends on the included [[transactions]]. This includes the generation transaction, a transaction "out of nowhere" to our own address, which in addition to providing the miner with incentive to do the work, also ensures that every miner hashes a unique data set.

[[Category:Vocabulary]]

[[fr:Preuve de travail]]

Proof of work

2013-03-08T19:37:23Z

Atheros: Hashcash stamps are not used in Bitcoin. Also this is not a Hashcash advertisement. Sorry Adam.

{{stub}}

A '''proof of work''' is a piece of data which was difficult (costly, time-consuming) to produce so as to satisfy certain requirements. It must be trivial to check whether data satisfies said requirements. Producing a proof of work can be a random process with low probability, so that a lot of trial and error is required ''on average'' before a valid proof of work is generated.

One application of this idea is a proposed [http://en.wikipedia.org/wiki/Hashcash method for preventing email spam], requiring a proof of work on the email's contents (including the To address), on every email. Legitimate emails will be able to do the work to generate the proof easily (not much work is required for a single email), but mass spam emailers will have difficulty generating the required proofs (which would require huge computational resources).

Proofs of work are used in Bitcoin for block generation. Proofs of work that are tied to the data of each block are required for the blocks to be accepted. The [[difficulty]] of this work is adjusted so as to limit the rate at which new blocks can be generated by the network to one every 10 minutes. Due to the very low probability of successful generation, this makes it unpredictable which worker computer in the network will be able to generate the next block.

For a block to be valid it must hash to a value less than the current [[target]]; this means that each block indicates that work has been done generating it. Each block contains the hash of the preceding block, thus each block has a [[block chain|chain]] of blocks that together contain a large amount of work. Changing a block (which can only be done by making a new block containing the same predecessor) requires regenerating all successors and redoing the work they contain. This protects the block chain from tampering.

== Example ==

Let's say the base string that we are going to do work on is "Hello, world!". Our target is to find a variation of it that SHA-256 hashes to a value beginning with '000'. We vary the string by adding an integer value to the end called a [[nonce]] and incrementing it each time. Finding a match for "Hello, world!" takes us 4251 tries (but happens to have zeroes in the first four digits):

"Hello, world!0" => 1312af178c253f84028d480a6adc1e25e81caa44c749ec81976192e2ec934c64
"Hello, world!1" => e9afc424b79e4f6ab42d99c81156d3a17228d6e1eef4139be78e948a9332a7d8
"Hello, world!2" => ae37343a357a8297591625e7134cbea22f5928be8ca2a32aa475cf05fd4266b7
...
"Hello, world!4248" => 6e110d98b388e77e9c6f042ac6b497cec46660deef75a55ebc7cfdf65cc0b965
"Hello, world!4249" => c004190b822f1669cac8dc37e761cb73652e7832fb814565702245cf26ebb9e6
"Hello, world!4250" => 0000c3af42fc31103f1fdc0151fa747ff87349a4714df7cc52ea464e12dcd4e9

4251 hashes on a modern computer is not very much work (most computers can achieve at least 4 million hashes per second). Bitcoin automatically varies the [[difficulty]] (and thus the amount of work required to generate a block) to keep a roughly constant rate of block generation. The probability of a single hash succeeding can be found [http://blockexplorer.com/q/probability here].

In Bitcoin things are a bit more complex, especially since the header contains the [http://en.wikipedia.org/wiki/Merkle_tree Merkle tree] which depends on the included [[transactions]]. This includes the generation transaction, a transaction "out of nowhere" to our own address, which in addition to providing the miner with incentive to do the work, also ensures that every miner hashes a unique data set.

[[Category:Vocabulary]]

[[fr:Preuve de travail]]

Help:FAQ

2013-03-08T19:23:57Z

Atheros: No one knows what a "cost function" is. This is inappropriate for a FAQ for newbies.

Here you will find answers to the most commonly asked questions.

== General ==
=== What are bitcoins? ===
Bitcoins are the unit of currency of the Bitcoin system. A commonly used shorthand for this is “BTC” to refer to a price or amount (eg: “100 BTC”).
There are such things as [[physical bitcoins]], but ultimately, a bitcoin is just a number associated with a [[Address|Bitcoin Address]]. A physical bitcoin is simply an object, such as a coin, with the number carefully embedded inside. See also an [[Introduction|easy intro]] to bitcoin.

=== How can I get bitcoins? ===

There are a variety of ways to acquire bitcoins:

* Accept bitcoins as payment for goods or services.
* There are several services where you can [[Buying_Bitcoins_(the_noob_version)|trade them]] for traditional currency.
* Find someone to trade cash for bitcoins in-person through a [https://en.bitcoin.it/wiki/Category:Directories local directory].
* Participate in a [[Pooled mining|mining pool]].
* If you have a lot of mining hardware, you can solo mine and attempt to create a new [[block]] (currently yields 25 bitcoins plus transaction fees).

===Does Bitcoin guarantee an influx of free money?===

Since Bitcoin is a new technology, what it is and how it works may be initially unclear. Bitcoin is sometimes presented as being one of three things:
<ol style="list-style-type: upper-alpha;">
<li>Some sort of online 'get-rich-quick' scam.</li>
<li>A loophole in the market economy, the installation of which guarantees a steady influx of cash.</li>
<li>A sure investment that will almost certainly yield a profit.</li>
</ol>
In fact, none of the above are true. Let's look at them independently.

;Is Bitcoin a 'get-rich-quick' scheme?
:If you've spent much time on the Internet, you've probably seen ads for many 'get-rich-quick' schemes. These ads usually promise huge profits for a small amounts of easy work. Such schemes are usually pyramid/matrix-style schemes that make money from their own employees and offer nothing of any real value. Most convince one to buy packages that will make them earn hundreds a day, which in fact have the buyer distribute more such ads, and make minute profits.

:Bitcoin is in no way similar to these schemes. Bitcoin doesn't promise windfall profits. There is no way for the developers to make money from your involvement or to take money from you. That bitcoins are nearly impossible to acquire without the owner's consent represents one of its greatest strengths. Bitcoin is an experimental, virtual currency that may succeed or may fail. None of its developers expect to get rich off of it.

:A more detailed answer to this question can be found [http://bitcointalk.org/?topic=7815.0 here].

;Will I make money by installing the client?
:Most people who use Bitcoin don't earn anything by doing so, and the default client has no built-in way to earn Bitcoins. A small minority of people with dedicated, high-performance hardware do earn some Bitcoins by "''mining''" (generating new bitcoins, see [[#What is mining?|What is mining?]]) with special software, but joining Bitcoin shouldn't be construed as being the road to riches. Most Bitcoin users get involved because they find the project conceptually interesting and don't earn anything by doing so. This is also why you won't find much speculation about the political or economic repercussions of Bitcoin anywhere on this site: Bitcoin developers owe their dedication to the project's intellectual yieldings more than to those of a monetary nature. Bitcoin is still taking its first baby steps; it may go on to do great things but right now it only has something to offer those chasing conceptually interesting projects or bleeding edge technology.

;As an investment, is Bitcoin a sure thing?
:Bitcoin is a new and interesting electronic currency, the value of which is not backed by any single government or organization. Like other currencies, it is worth something partly because people are willing to trade it for goods and services. Its exchange rate fluctuates continuously, and sometimes wildly. It lacks wide acceptance and is vulnerable to manipulation by parties with modest funding. Security incidents such as website and account compromise may trigger major sell-offs. Other fluctuations can build into positive feedback loops cause much larger exchange rate fluctuations. Anyone who puts money into Bitcoin should take measures to reduce their risk and consider it as a high-risk currency. Later, as Bitcoin becomes better known and more widely accepted, it should stabilize, but for the time being it is unpredictable. Any investment in Bitcoin should be done carefully and with a clear plan to manage risk.

=== Can I buy bitcoins with Paypal? ===

It is possible to buy [[physical bitcoins]] with PayPal but it is otherwise difficult and/or expensive to do so, because of significant risk to the seller.

While it is possible to find an individual who wishes to sell Bitcoin to you via Paypal, (perhaps via [http://www.bitcoin-otc.com/ #bitcoin-otc] ) most exchanges do not allow funding through PayPal. This is due to repeated cases where someone pays for bitcoins with Paypal receives their bitcoins, and then fraudulently complains to Paypal that they never received their purchase. PayPal often sides with the fraudulent buyer in this case which means any seller would need to cover that risk with higher fees or refuse to accept PayPal altogether.

Buying Bitcoins from individuals with this method is still possible, but requires the seller to have some trust that the buyer will not file a claim with PayPal to reverse the payment.

=== Where can I find a forum to discuss Bitcoin? ===

Please visit the [[Bitcoin:Community_portal#Bitcoin_Community_Forums_on_various_platforms|Community Portal]] for links to Bitcoin-related forums.

=== How are new bitcoins created? ===

[[File:total_bitcoins_over_time_graph.png|thumb|Number of bitcoins over time, assuming a perfect 10-minute interval.]]
New bitcoins are generated by the network through the process of "[[#What is mining?|''mining'']]". In a process that is similar to a continuous raffle draw, mining nodes on the network are awarded bitcoins each time they find the solution to a certain mathematical problem (and thereby create a new [[block]]). Creating a block is a [[proof of work]] with a difficulty that varies with the overall strength of the network. The reward for solving a block is [[Controlled Currency Supply|automatically adjusted]] so that in roughly the first four years of operation of the Bitcoin network, {{formatnum:10500000}} BTC will be created. This amount is halved each four years, so it will be {{formatnum:5250000}} over years 4-8, {{formatnum:2625000}} over years 8-12, and so on. Thus the total number of bitcoins in existence will not exceed {{formatnum:21000000}}. See [[Controlled Currency Supply]].

Blocks are [[Mining|mined]] every 10 minutes, on average and for the first four years ({{formatnum:210000}} blocks) each block includes 50 new bitcoins. As the amount of processing power directed at mining changes, the difficulty of creating new bitcoins changes. This difficulty factor is calculated every 2016 blocks and is based upon the time taken to generate the previous 2016 blocks. See [[Mining]].

=== What's the current total number of bitcoins in existence? ===

[http://blockexplorer.com/q/totalbc Current count]. Also see [https://blockchain.info/charts/total-bitcoins Total bitcoins in circulation chart]

The number of blocks times the coin value of a block is the number of coins in existence. The coin value of a block is 50 BTC for each of the first {{formatnum:210000}} blocks, 25 BTC for the next {{formatnum:210000}} blocks, then 12.5 BTC, 6.25 BTC and so on.

=== How divisible are bitcoins? ===

A bitcoin can be divided down to 8 decimal places. Therefore, 0.00000001 BTC is the smallest amount that can be handled in a transaction. If necessary, the protocol and related software can be modified to handle even smaller amounts.

=== What do I call the various denominations of bitcoins? ===

There is a lot of discussion about the naming of these fractions of bitcoins. The leading candidates are:

* 1 BTC = 1 bitcoin
* 0.01 BTC = 1 cBTC = 1 centibitcoin (also referred to as bitcent)
* 0.001 BTC = 1 mBTC = 1 millibitcoin (also referred to as mbit (pronounced em-bit) or millibit or even bitmill)
* 0.000 001 BTC = 1 μBTC = 1 microbitcoin (also referred to as ubit (pronounced yu-bit) or microbit)

The above follows the accepted international SI prefixes for hundredths, thousandths, and millionths. There are many arguments against the special case of 0.01 BTC since it is unlikely to represent anything meaningful as the Bitcoin economy grows (it certainly won't be the equivalent of 0.01 USD, GBP or EUR). Equally, the inclusion of existing national currency denominations such as "cent", "nickel", "dime", "pence", "pound", "kopek" and so on are to be discouraged; this is a worldwide currency.

One exception is the "satoshi" which is smallest denomination currently possible

* 0.000 000 01 BTC = 1 satoshi (pronounced sa-toh-shee)
which is so named in honour of Satoshi Nakamoto, the pseudonym of the inventor of Bitcoin.

For an overview of all defined units of Bitcoin (including less common and niche units), see [[Units]].

Further discussion on this topic can be found on the forums here:

* [https://bitcointalk.org/index.php?topic=14438.msg195287#msg195287 We need names]
* [https://bitcointalk.org/index.php?topic=8282.0 What to call 0.001 BTC]

=== How does the halving work when the number gets really small? ===

Eventually the reward will go from 0.00000001 BTC to zero and no more bitcoins will be created.

The block reward calculation is done as a right bitwise shift of a 64-bit signed integer, which means it is divided by two and rounded down. The integer is equal to the value in BTC * 100,000,000 since internally in the reference client software, all Bitcoin balances and values are stored as unsigned integers.

With an initial block reward of 50 BTC, it will take many 4-year periods for the block reward to reach zero.

=== How long will it take to generate all the coins? ===

The last block that will generate coins will be block #6,929,999 which should be generated at or near the year 2140. The total number of coins in circulation will then remain static at 20,999,999.9769 BTC.

Even if the allowed precision is expanded from the current 8 decimals, the total BTC in circulation will always be slightly below 21 million (assuming everything else stays the same). For example, with 16 decimals of precision, the end total would be 20,999,999.999999999496 BTC.

=== If no more coins are going to be generated, will more blocks be created? ===

Absolutely! Even before the creation of coins ends, the use of [[transaction fee|transaction fees]] will likely make creating new blocks more valuable from the fees than the new coins being created. When coin generation ends, these fees will sustain the ability to use bitcoins and the Bitcoin network. There is no practical limit on the number of blocks that will be mined in the future.

=== But if no more coins are generated, what happens when Bitcoins are lost? Won't that be a problem? ===

Because of the law of supply and demand, when fewer bitcoins are available the ones that are left will be in higher demand, and therefore will have a higher value. So, as Bitcoins are lost, the remaining bitcoins will eventually increase in value to compensate. As the value of a bitcoin increases, the number of bitcoins required to purchase an item '''de'''creases. This is a [[Deflationary spiral|deflationary economic model]]. As the average transaction size reduces, transactions will probably be denominated in sub-units of a bitcoin such as millibitcoins ("Millies") or microbitcoins ("Mikes").

The Bitcoin protocol uses a base unit of one hundred-millionth of a Bitcoin ("a Satoshi"), but unused bits are available in the protocol fields that could be used to denote even smaller subdivisions.

=== If every transaction is broadcast via the network, does Bitcoin scale? ===
The Bitcoin protocol allows lightweight clients that can use Bitcoin without downloading the entire transaction history. As traffic grows and this becomes more critical, implementations of the concept will be developed. Full network nodes will at some point become a more specialized service.

With some modifications to the software, full Bitcoin nodes could easily keep up with both VISA and MasterCard combined, using only fairly modest hardware (a single high end server by todays standards). It is worth noting that the MasterCard network is structured somewhat like Bitcoin itself - as a peer to peer broadcast network.

Learn more about [[Scalability]].

==Economy==
=== Where does the value of Bitcoin stem from? What backs up Bitcoin? ===
Bitcoins have value because they are useful and because they are [[Controlled Currency Supply|scarce]]. As they are accepted by more merchants, their value will [http://en.wikipedia.org/wiki/Sticky_%28economics%29 stabilize]. See the [[Trade|list of Bitcoin-accepting sites]].

When we say that a currency is backed up by gold, we mean that there's a promise in place that you can exchange the currency for gold. Bitcoins, like dollars and euros, are not backed up by anything except the variety of merchants that accept them.

It's a common misconception that Bitcoins gain their value from the cost of electricity required to generate them. Cost doesn't equal value – hiring 1,000 men to shovel a big hole in the ground may be costly, but not valuable. Also, even though scarcity is a critical requirement for a useful currency, it alone doesn't make anything valuable. For example, your fingerprints are scarce, but that doesn't mean they have any exchange value.

Alternatively it needs to be added that while the law of supply and demand applies it does not guarantee value of Bitcoins in the future. If confidence in Bitcoins is lost then it will not matter that the supply can no longer be increased, the demand will fall off with all holders trying to get rid of their coins. An example of this can be seen in cases of state currencies, in cases when the state in question dissolves and so no new supply of the currency is available (the central authority managing the supply is gone), however the demand for the currency falls sharply because confidence in its purchasing power disappears. Of-course Bitcoins do not have such central authority managing the supply of the coins, but it does not prevent confidence from eroding due to other situations that are not necessarily predictable.

=== Is Bitcoin a bubble? ===
Yes, in the same way as the euro and dollar are. They only have value in exchange and have no inherent value. If everyone suddenly stopped accepting your dollars, euros or bitcoins, the "bubble" would burst and their value would drop to zero. But that is unlikely to happen: even in Somalia, where the government collapsed 20 years ago, [http://en.wikipedia.org/wiki/Somali_shilling Somali shillings] are still accepted as payment.

=== Is Bitcoin a Ponzi scheme? ===
In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. Early adopters can only profit at the expense of late adopters. Bitcoin has possible win-win outcomes. Early adopters profit from the rise in value. Late adopters, and indeed, society as a whole, benefit from the usefulness of a stable, fast, inexpensive, and widely accepted p2p currency.

The fact that early adopters benefit more doesn't alone make anything a Ponzi scheme. All good investments in successful companies have this quality.

=== Doesn't Bitcoin unfairly benefit early adopters? ===
Early adopters have a large number of bitcoins now because they took a risk and invested resources in an unproven technology. By so doing, they have helped Bitcoin become what it is now and what it will be in the future (hopefully, a ubiquitous decentralized digital currency). It is only fair they will reap the benefits of their successful investment.

In any case, any bitcoin generated will probably change hands dozens of time as a medium of exchange, so the profit made from the initial distribution will be insignificant compared to the total commerce enabled by Bitcoin.

Since the pricing of Bitcoins has fallen greatly from its June 2011 peak, prices today are much more similar to those enjoyed by many early adopters. Those who are buying Bitcoins today likely believe that Bitcoin will grow significantly in the future. Setting aside the brief opportunity to have sold Bitcoins at the June 2011 peak enjoyed by few, the early-adopter window is arguably still open.

===Won't loss of wallets and the finite amount of Bitcoins create excessive deflation, destroying Bitcoin? ===
Worries about Bitcoin being destroyed by deflation are not entirely unfounded. Unlike most currencies, which experience inflation as their founding institutions create more and more units, Bitcoin will likely experience gradual deflation with the passage of time. Bitcoin is unique in that only a small amount of units will ever be produced (twenty-one million to be exact), this number has been known since the project's inception, and the units are created at a predicable rate.

Also, Bitcoin users are faced with a danger that doesn't threaten users of any other currency: if a Bitcoin user loses his wallet, his money is gone forever, unless he finds it again. And not just to him; it's gone completely out of circulation, rendered utterly inaccessible to anyone. As people will lose their wallets, the total number of Bitcoins will slowly decrease.

Therefore, Bitcoin seems to be faced with a unique problem. Whereas most currencies inflate over time, Bitcoin will mostly likely do the just the opposite. Time will see the irretrievable loss of an ever-increasing number of Bitcoins. An already small number will be permanently whittled down further and further. And as there become fewer and fewer Bitcoins, the laws of supply and demand suggest that their value will probably continually rise.

Thus Bitcoin is bound to once again stray into mysterious territory, because no one exactly knows what happens to a currency that grows continually more valuable. Economists generally agree that a low level of inflation is a good thing for a currency, but nobody is quite sure about what might happens to one that continually deflates. Although deflation could hardly be called a rare phenomenon, steady, constant deflation is unheard of. There may be a lot of speculation, no one has any hard data to back up their claims.

That being said, there is a mechanism in place to combat the obvious consequences. Extreme deflation would render most currencies highly impractical: if a single Canadian dollar could suddenly buy the holder a car, how would one go about buying bread or candy? Even pennies would fetch more than a person could carry. Bitcoin, however, offers a simple and stylish solution: infinite divisibility. Bitcoins can be divided up and trade into as small of pieces as one wants, so no matter how valuable Bitcoins become, one can trade them in practical quantities.

In fact, infinite divisibility should allow Bitcoins to function in cases of extreme wallet loss. Even if, in the far future, so many people have lost their wallets that only a single Bitcoin, or a fraction of one, remains, Bitcoin should continue to function just fine. No one can claim to be sure what is going to happen, but deflation may prove to present a smaller threat than many expect.

For more information, see the [[Deflationary spiral]] page.

=== What if someone bought up all the existing Bitcoins? ===
Bitcoin markets are competitive -- meaning the price of a bitcoin will rise or fall depending on supply and demand at certain price levels. Only a fraction of bitcoins issued to date are found on the exchange markets for sale. So even though technically a buyer with lots of money could buy all the bitcoins offered for sale, unless those holding the rest of the bitcoins offer them for sale as well, even the wealthiest, most determined buyer can't get at them.

Additionally, new currency continues to be issued daily and will continue to do so for decades though over time the rate at which they are issued declines to insignificant levels. Those who are mining aren't obligated to sell their bitcoins so not all bitcoins will make it to the markets even.

This situation doesn't suggest, however, that the markets aren't vulnerable to price manipulation. It doesn't take significant amounts of money to move the market price up or down and thus Bitcoin remains a volatile asset.

===What if someone creates a new block chain, or a new digital currency that renders Bitcoin obsolete?===

That the block chain cannot be easily forked represents one of the central security mechanisms of Bitcoin. Given the choice between two block chains, a Bitcoin miner always chooses the longer one - that is to say, the one with the more complex hash. Thusly, it ensures that each user can only spend their bitcoins once, and that no user gets ripped off.

As a consequence of the block chain structure, there may at any time be many different sub-branches, and the possibility always exists of a transaction being over-written by the longest branch, if it has been recorded in a shorter one. The older a transaction is though, the lower its chances of being over-written, and the higher of becoming permanent. Although the block chain prevents one from spending more Bitcoins than one has, it means that transactions can be accidentally nullified.

A new block chain would leave the network vulnerable to [[double-spending|double-spend]] attacks. However, the creation of a viable new chain presents considerable difficulty, and the possibility does not present much of a risk.

Bitcoin will always choose the longer Block Chain and determines the relative length of two branches by the complexities of their hashes. Since the hash of each new block is made from that of the block preceding it, to create a block with a more complex hash, one must be prepared to do more computation than has been done by the entire Bitcoin network from the fork point up to the newest of the blocks one is trying to supersede. Needless to say, such an undertaking would require a very large amount of processing power and since Bitcoin is continually growing and expanding, it will likely only require more with the passage of time.

A much more distinct and real threat to the Bitcoin use is the development of other, superior virtual currencies, which could supplant Bitcoin and render it obsolete and valueless.

A great deal of careful thought and ingenuity has gone into the development of Bitcoin, but it is the first of its breed, a prototype, and vulnerable to more highly-evolved competitors. At present, any threatening rivals have yet to rear its head; Bitcoin remains the first and foremost private virtual currency, but we can offer no guarantees that it will retain that position. It would certainly be in keeping with internet history for similar system built from the same principles to supersede and cast Bitcoin into obsolescence, after time had revealed its major shortcomings. Friendster and Myspace suffered similar fates at the hand of Facebook, Napster was ousted by Limeware, Bearshare and torrent applications, and Skype has all but crushed the last few disciples of the Microsoft Messenger army.

This may sound rather foreboding, so bear in mind that introduction of new and possibly better virtual currencies will not necessarily herald Bitcoin's demise. If Bitcoin establishes itself sufficiently firmly before the inception of the next generation of private, online currencies as to gain widespread acceptance and general stability, future currencies may pose little threat even if they can claim superior design.

==Sending and Receiving Payments==

=== Why do I have to wait 10 minutes before I can spend money I received? ===

10 minutes is the average time taken to find a block. It can be significantly more or less time than that depending on luck; 10 minutes is simply the average case.

You can see how long all other recent transactions have taken here: [http://bitcoinstats.org/ BitcoinStats.org].

[[Blocks]] (shown as "confirmations" in the GUI) are how the Bitcoin achieves consensus on who owns what. Once a block is found everyone agrees that you now own those coins, so you can spend them again. Until then it's possible that some network nodes believe otherwise, if somebody is attempting to defraud the system by reversing a transaction. The more confirmations a transaction has, the less risk there is of a reversal. Only 6 blocks or 1 hour is enough to make reversal computationally impractical. This is dramatically better than credit cards which can see chargebacks occur up to three months after the original transaction!

Ten minutes was specifically chosen by [[Satoshi]] as a tradeoff between propagation time of new blocks in large networks and the amount of work wasted due to chain splits. For a more technical explanation, see Satoshi's [http://www.bitcoin.org/bitcoin.pdf original technical paper].

[[File:TransactionConfirmationTimesExample.PNG]]

=== Do you have to wait until my transactions are confirmed in order to buy or sell things with Bitcoin? ===

YES, you do, IF the transaction is non-recourse. The Bitcoin reference software does not display transactions as confirmed until six blocks have passed (confirmations). As transactions are burred in the chain they become increasingly non-reversible but are very reversible before the first confirmation. Two to six confirmations are recommended for non-recourse situations depending on the value of the transactions involved.

When people ask this question they are usually thinking about applications like supermarkets. This generally is a recourse situation: if somebody tries to double-spend on a face-to-face transaction it might work a few times, but probabalistically speaking eventually one of the double-spends will get noticed, and the penalty for shoplifting charges in most localities is calibrated to be several times worse than the proceeds of a single shoplifting event.

Double-spends might be a concern for something like a snack machine in a low-traffic area with no nearby security cameras. Such a machine shouldn't honor 0-confirmation payments, and should instead use some other mechanism of clearing Bitcoin or validating transactions against reversal, see the wiki article [[Myths#Point_of_sale_with_bitcoins_isn.27t_possible_because_of_the_10_minute_wait_for_confirmation|here]] for alternatives.

Applications that require immediate payment processing, like supermarkets or snack machines, need to manage the risks. Here is one way to reverse an unconfirmed payment:

A [[Double-spending#Finney_attack|Finney attack]], in which an attacker mines a block containing a movement of some coins back to themselves. Once they find a block solution, they quickly go to a merchant and make a purchase, then broadcast the block, thus taking back the coins. This attack is a risk primarily for goods that are dispatched immediately, like song downloads or currency trades. Because the attacker can't choose the time of the attack, it isn't a risk for merchants such as supermarkets where you can't choose exactly when to pay (due to queues, etc). The attack can fail if somebody else finds a block containing the purchasing transaction before you release your own block, therefore, merchants can reduce but not eliminate the risk by making purchasers wait some length of time that's less than a confirm.

Because pulling off this attack is not trivial, merchants who need to sell things automatically and instantly are most likely to just price the cost of reversal fraud in, or use insurance.

=== I was sent some bitcoins and they haven't arrived yet! Where are they? ===

Don't panic! There are a number of reasons why your bitcoins might not show up yet, and a number of ways to diagnose them.

The latest version of the Bitcoin-Qt client tells you how far it has yet to go in downloading the blockchain. Hover over the icon in the bottom right corner of the client to learn your client's status.

If it has not caught up then it's possible that your transaction hasn't been included in a block yet.

You can check pending transactions in the network by going [http://blockchain.info here] and then searching for your address. If the transaction is listed here then it's a matter of waiting until it gets included in a block before it will show in your client.

If the transaction is based on a coin that was in a recent transaction then it could be considered a low priority transaction. Transfers can take longer if the transaction fee paid was not high enough. If there is no fee at all the transfer can get a very low priority and take hours or even days to be included in a block.

=== Why does my Bitcoin address keep changing? ===

Whenever the address listed in "Your address" receives a transaction, Bitcoin replaces it with a new address. This is meant to encourage you to use a new address for every transaction, which enhances [[anonymity]]. All of your old addresses are still usable: you can see them in ''Settings -> Your Receiving Addresses''.

===How much will the transaction fee be?===

Some transactions might require a [[transaction fee]] for them to get confirmed in a timely manner. The transaction fee is processed by and received by the bitcoin miner. The most recent version of the Bitcoin client will estimate an appropriate fee when a fee might be required.

The fee is added to the payment amount. For example, if you are sending a 1.234 BTC payment and the client requires a 0.0005 BTC fee, then 1.2345 BTC will be subtracted from the wallet balance for the entire transaction and the address for where the payment was sent will receive a payment of 1.234 BTC.

A fee might be imposed because your transaction looks like a denial of service attack to the Bitcoin system. For example, it might be burdensome to transmit or it might recycle Bitcoins you recently received. The wallet software attempts to avoid generating burdensome transactions, but it isn't always able to do so: The funds in your wallet might be new or composed of many tiny payments.

Because the fee is related to the amount of data that makes up the transaction and not to the amount of Bitcoins being sent, the fee may seem extremely low (0.0005 BTC for a 1,000 BTC transfer) or unfairly high (0.004 BTC for a 0.02 BTC payment, or about 20%). If you are receiving tiny amounts (''e.g.'' as small payments from a mining pool) then fees when sending will be higher than if your activity follows the pattern of conventional consumer or business transactions.

As of Bitcoin 0.5.3 the required fee will not be higher than 0.05 BTC. For most users there is usually no required fee at all. If a fee is required it will most commonly be 0.0005 BTC.

=== What happens when someone sends me a bitcoin but my computer is powered off? ===

Bitcoins are not actually "sent" to your wallet; the software only uses that term so that we can use the currency without having to learn new concepts. Your wallet is only needed when you wish to spend coins that you've received.

If you are sent coins when your wallet client program is not running, and you later launch the wallet client program, the coins will eventually appear as if they were just received in the wallet. That is to say, when the client program is started it must download blocks and catch up with any transactions it did not already know about.

=== How long does "synchronizing" take when the Bitcoin client is first installed? What's it doing? ===

The popular Bitcoin client software from bitcoin.org implements a "full" Bitcoin node: It can carry out all the duties of the Bitcoin P2P system, it isn't simply a "client". One of the principles behind the operation of full Bitcoin nodes is that they don't assume that the other participants have followed the rules of the Bitcoin system. During synchronization, the software is processing historical Bitcoin transactions and making sure for itself that all of the rules of the system have been correctly followed.

In normal operation, after synchronizing, the software should use a hardly noticeable amount of your computer's resources.

When the wallet client program is first installed, its initial validation requires a lot of work from your computer's hard disk, so the amount of time to synchronize depends on your disk speed and, to a lesser extent, your CPU speed. It can take anywhere from a few hours to a day or so. On a slow computer it could take more than 40 hours of continuous synchronization, so check your computer's power-saving settings to ensure that it does not turn its hard disk off when unattended for a few hours. You can use the Bitcoin software during synchronization, but you may not see recent payments to you until the client program has caught up to the point where those transactions happened.

If you feel that this process takes too long, you can download a pre-synchronized blockchain from [http://eu2.bitcoincharts.com/blockchain/ http://eu2.bitcoincharts.com/blockchain/]. Alternatively, you can try an alternative "lite" client such as Multibit or a super-light client like electrum, though these clients have somewhat weaker security, are less mature, and don't contribute to the health of the P2P network.

==Networking==
=== Do I need to configure my firewall to run Bitcoin? ===

Bitcoin will connect to other nodes, usually on TCP port 8333. You will need to allow outgoing TCP connections to port 8333 if you want to allow your Bitcoin client to connect to many nodes. [[Testnet]] uses TCP port 18333 instead of 8333.

If you want to restrict your firewall rules to a few IPs, you can find stable nodes in the [[Fallback Nodes|fallback nodes list]].

=== How does the peer finding mechanism work? ===

Bitcoin finds peers primarily by forwarding peer announcements within its own network and each node saves a database of peers that it's aware of, for future use. In order to bootstrap this process Bitcoin needs a list of initial peers, these can be provided manually but normally it obtains them by querying a set of DNS domain names which have automatically updated lists, if that doesn't work it falls back to a build-in list which is updated from time to time in new versions of the software. There is also an IRC based mechanism but it is disabled by default.

==Mining==
===What is mining?===
[[Mining]] is the process of spending computation power to secure Bitcoin transactions against reversal and introducing new Bitcoins to the system.

Technically speaking, mining is the calculation of a [[hash]] of the a block header, which includes among other things a reference to the previous block, a hash of a set of transactions and a [[nonce]]. If the hash value is found to be less than the current [[target]] (which is inversely proportional to the [[difficulty]]), a new block is formed and the miner gets the newly generated Bitcoins (25 per block at current levels). If the hash is not less than the current target, a new nonce is tried, and a new hash is calculated. This is done millions of times per second by each miner.

===Is mining used for some useful computation?===
The computations done when mining are internal to Bitcoin and not related to any other distributed computing projects. They serve the purpose of securing the Bitcoin network, which is useful.

===Is it not a waste of energy?===
Spending energy on creating and securing a free monetary system is hardly a waste. Also, services necessary for the operation of currently widespread monetary systems, such as banks and credit card companies, also spend energy, arguably more than Bitcoin would.

===Why don't we use calculations that are also useful for some other purpose?===
To provide security for the Bitcoin network, the calculations involved need to have some [http://bitcoin.stackexchange.com/questions/5617/why-are-bitcoin-calculation-useless/5618#5618 very specific features]. These features are incompatible with leveraging the computation for other purposes.

===How can we stop miners from creating zero transaction blocks?===
The incentive for miners to include transactions is in the fees that come along with them. If we were to implement some minimum number of transactions per block it would be trivial for a miner to create and include transactions merely to surpass that threshold. As the network matures, the block reward drops, and miners become more dependent on transactions fees to pay their costs, the problem of zero transaction blocks should diminish over time.

===How does the proof-of-work system help secure Bitcoin?===
To give a general idea of the mining process, imagine this setup:

payload = <some data related to things happening on the Bitcoin network>
nonce = 1
hash = [http://en.wikipedia.org/wiki/SHA2 SHA2]( [http://en.wikipedia.org/wiki/SHA2 SHA2]( payload + nonce ) )

The work performed by a miner consists of repeatedly increasing "nonce" until
the hash function yields a value, that has the rare property of being below a certain
target threshold. (In other words: The hash "starts with a certain number of zeroes",
if you display it in the fixed-length representation, that is typically used.)

As can be seen, the mining process doesn't compute anything special. It merely
tries to find a number (also referred to as nonce) which - in combination with the payload -
results in a hash with special properties.

The advantage of using such a mechanism consists of the fact, that it is very easy to check a result: Given the payload and a specific nonce, only a single call of the hashing function is needed to verify that the hash has the required properties. Since there is no known way to find these hashes other than brute force, this can be used as a "proof of work" that someone invested a lot of computing power to find the correct nonce for this payload.

This feature is then used in the Bitcoin network to secure various aspects. An attacker
that wants to introduce malicious payload data into the network, will need to do the
required proof of work before it will be accepted. And as long as honest miners have more
computing power, they can always outpace an attacker.

Also see [http://en.wikipedia.org/wiki/Hashcash Hashcash] and [http://en.wikipedia.org/wiki/Proof-of-work_system Proof-of-work system] and [http://en.wikipedia.org/wiki/SHA2 SHA2] and on Wikipedia.

===Why was the "Generate coin" option of the client software removed?===

In the early days of Bitcoin, it was easy for anyone to find new blocks using standard CPUs. As more and more people started mining, the [[difficulty]] of finding new blocks has greatly increased to the point where the average time for a CPU to find a single block can be many years. The only cost-effective method of [[Mining|mining]] is using a high-end graphics card with special software (see also [[Why a GPU mines faster than a CPU]]) and/or joining a [[Bitcoin Pool|mining pool]]. Since solo CPU mining is essentially useless, it was removed from the GUI of the Bitcoin software.

==Security==

===Could miners collude to give themselves money or to fundamentally change the nature of Bitcoin?===

There are two questions in here. Let's look at them separately.

;Could miners gang up and give themselves money?

Mining itself is the process of creating new blocks in the block chain. Each block contains a list of all the transactions that have taken place across the entire Bitcoin network since the last block was created, as well as a hash of the previous block. New blocks are 'mined', or rather, generated, by Bitcoin clients correctly guessing sequences of characters in codes called 'hashes,' which are created using information from previous blocks. Bitcoin users may download specialized 'mining' software, which allows them to dedicate some amount of their processing power – however large or small – to guessing at strings within the hash of the previous block. Whoever makes the right guess first, thus creating a new block, receives a reward in Bitcoins.

The block chain is one of the two structures that makes Bitcoin secure, the other being the public-key encryption system on which Bitcoin trade is based. The block chain assures that not only is every single transaction that ever takes place recorded, but that every single transaction is recorded on the computer of anyone who chooses to store the relevant information. Many, many users have complete records of every transaction in Bitcoins history readily available to them at any point, and anyone who wants in the information can obtain it with ease. These things make Bitcoin very hard to fool.

The Bitcoin network takes considerable processing power to run, and since those with the most processing power can make the most guesses, those who put the most power toward to sustaining the network earn the most currency. Each correct guess yields, at present, fifty Bitcoins, and as Bitcoins are presently worth something (although the value still fluctuates) every miner who earns any number of Bitcoins makes money. Some miners pull in Bitcoins on their own; and some also join or form pools wherein all who contribute earn a share of the profits.

Therefore, first answer is a vehement “yes” – no only can miners collude to get more money, Bitcoin is designed to encourage them to do so. Bitcoin pools are communal affairs, and there is nothing dishonest or underhanded about them.

Of course, the real question is:

;Can they do so in ways not sanction by Bitcoin developers? Is there any way to rip off the network and make loads of money dishonestly?

Bitcoin isn't infallible. It can be cheated, but doing so is extremely difficult. Bitcoin was designed to evade some of the central problems with modern currencies – namely, that their trustworthiness hinges upon that of people who might not have users' best interests in mind. Every currency in the world (other than Bitcoin) is controlled by large institutions who keep track of what's done with it, and who can manipulate its value. And every other currency has value because people trust the institutions that control them.

Bitcoin doesn't ask that its users trust any institution. Its security is based on the cryptography that is an integral part of its structure, and that is readily available for any and all to see. Instead of one entity keeping track of transactions, the entire network does, so Bitcoins are astoundingly difficult to steal, or double-spend. Bitcoins are created in a regular and predictable fashion, and by many different users, so no one can decide to make a whole lot more and lessen their value. In short, Bitcoin is designed to be inflation-proof, double-spend-proof and completely distributed.

Nonetheless, there are a few ways that one can acquire Bitcoins dishonestly. Firstly, one can steal private keys. Key theft isn't something that Bitcoin security has been designed to prevent: it's up to users to keep theirs safe. But the cryptography is designed so that it is completely impossible to deduce someone's private key from their public one. As long as you keep your private key to yourself, you don't have much to worry about. Furthermore, one could theoretically create a new block chain, but due to the way in which the block chain is constructed, this would be extremely difficult and require massive amounts of processing power. A full explanation of the difficulties involved can be found in the [[block chain]] article.

Bitcoin can be ripped off – but doing so would be extremely hard and require considerable expertise and a staggering amount of processing power. And it's only going to get harder with time. Bitcoin isn't impenetrable, but it's close enough to put any real worries in the peripherals.

;Could miners fundamentally change the nature of Bitcoin?

Once again, almost certainly not.

Bitcoin is a distributed network, so any changes implemented to the system must be accepted by all users. Someone trying to change the way Bitcoins are generated would have to convince every user to download and use their software – so the only changes that would go through are those that would be equally benefit all users.

And thus, it is more or less impossible for anyone to change the function of Bitcoin to their advantage. If users don't like the changes, they won't adopt them, whereas if users do like them, then these will help everyone equally. Of course, one can conceive of a situation where someone manages to get a change pushed through that provides them with an advantage that no one notices, but given that Bitcoin is structurally relatively simple, it is unlikely that any major changes will go through without someone noticing first.

The fact that such changes are so difficult to make testifies to the fully distributed nature of Bitcoin. Any centrally controlled currency can be modified by its central agency without the consent of its adherents. Bitcoin has no central authority, so it changes only at the behest of the whole community. Bitcoins development represents a kind of collective evolution; the first of its kind among currencies.

==Help==
===I'd like to learn more. Where can I get help?===

* Read the [[Introduction|introduction to bitcoin]]
* See the videos, podcasts, and blog posts from the [[Press]]
* Read and post on the [[Bitcoin:Community_portal#Bitcoin_Community_Forums|forums]]
* Chat on one of the [[Bitcoin:Community_portal#IRC_Chat|Bitcoin IRC]] channels
* Listen to [http://omegataupodcast.net/2011/03/59-bitcoin-a-digital-decentralized-currency/ this podcast], which goes into the details of how bitcoin works
* Ask questions on the [http://bitcoin.stackexchange.com Bitcoin Stack Exchange]

==See Also==

* [[Man page]]
* [[Introduction]]

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