Bitcoin Wiki - User contributions [en]

Genesis block

2013-06-01T12:04:02Z

Willphase: add link to image of front page

{{stub}}

A '''genesis block''' is the first block of a [[block chain]]. Modern versions of Bitcoin assign it block number 0, though older versions gave it number 1.

== Main network genesis block ==
[http://blockexplorer.com/block/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f The block on Bitcoin Block Explorer]

Here is a representation of the genesis block as it appeared in a comment in an old version of Bitcoin ([http://bitcoin.svn.sourceforge.net/viewvc/bitcoin/trunk/main.cpp?revision=133&view=markup&pathrev=170 line 1613]). The first section defines exactly all of the variables necessary to recreate the block. The second section is the block in standard printblock format, which contains shortened versions of the data in the first section.

GetHash() = 0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
hashMerkleRoot = 0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b
txNew.vin[0].scriptSig = 486604799 4 0x736B6E616220726F662074756F6C69616220646E6F63657320666F206B6E697262206E6F20726F6C6C65636E61684320393030322F6E614A2F33302073656D695420656854
txNew.vout[0].nValue = 5000000000
txNew.vout[0].scriptPubKey = 0x5F1DF16B2B704C8A578D0BBAF74D385CDE12C11EE50455F3C438EF4C3FBCF649B6DE611FEAE06279A60939E028A8D65C10B73071A6F16719274855FEB0FD8A6704 OP_CHECKSIG
block.nVersion = 1
block.nTime = 1231006505
block.nBits = 0x1d00ffff
block.nNonce = 2083236893

CBlock(hash=000000000019d6, ver=1, hashPrevBlock=00000000000000, hashMerkleRoot=4a5e1e, nTime=1231006505, nBits=1d00ffff, nNonce=2083236893, vtx=1)
CTransaction(hash=4a5e1e, ver=1, vin.size=1, vout.size=1, nLockTime=0)
CTxIn(COutPoint(000000, -1), coinbase 04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73)
CTxOut(nValue=50.00000000, scriptPubKey=0x5F1DF16B2B704C8A578D0B)
vMerkleTree: 4a5e1e

The coinbase parameter (seen above in hex) contains, along with the normal data, the following text<ref>[http://uk.reuters.com/article/idUKPTIP32510920090103 Reuters' reference on The Financial Times article]</ref>:

The Times 03/Jan/2009 Chancellor on brink of second bailout for banks<ref>[http://i.imgur.com/tWCACH5.jpg Front page of the London Times, 03 Jan 2009]</ref>

This was probably intended as proof that the block was created on or after January 3rd, 2009, as well as a comment on the instability caused by fractional-reserve banking.

The first 50BTC block reward went to [[address]] [http://blockexplorer.com/address/1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa], though this reward can't be spent due to a quirk in the way that the genesis block is expressed in the code (this may have been intentional).

==Raw block data==

The [https://bitcointalk.org/index.php?topic=52706 raw hex version] of the Genesis block looks like:
00000000 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000020 00 00 00 00 3B A3 ED FD 7A 7B 12 B2 7A C7 2C 3E ....;£íýz{.²zÇ,>
00000030 67 76 8F 61 7F C8 1B C3 88 8A 51 32 3A 9F B8 AA gv.a.È.ÃˆŠQ2:Ÿ¸ª
00000040 4B 1E 5E 4A 29 AB 5F 49 FF FF 00 1D 1D AC 2B 7C K.^J)«_Iÿÿ...¬+|
00000050 01 01 00 00 00 01 00 00 00 00 00 00 00 00 00 00 ................
00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000070 00 00 00 00 00 00 FF FF FF FF 4D 04 FF FF 00 1D ......ÿÿÿÿM.ÿÿ..
00000080 01 04 45 54 68 65 20 54 69 6D 65 73 20 30 33 2F ..EThe Times 03/
00000090 4A 61 6E 2F 32 30 30 39 20 43 68 61 6E 63 65 6C Jan/2009 Chancel
000000A0 6C 6F 72 20 6F 6E 20 62 72 69 6E 6B 20 6F 66 20 lor on brink of
000000B0 73 65 63 6F 6E 64 20 62 61 69 6C 6F 75 74 20 66 second bailout f
000000C0 6F 72 20 62 61 6E 6B 73 FF FF FF FF 01 00 F2 05 or banksÿÿÿÿ..ò.
000000D0 2A 01 00 00 00 43 41 04 67 8A FD B0 FE 55 48 27 *....CA.gŠý°þUH'
000000E0 19 67 F1 A6 71 30 B7 10 5C D6 A8 28 E0 39 09 A6 .gñ¦q0·.\Ö¨(à9.¦
000000F0 79 62 E0 EA 1F 61 DE B6 49 F6 BC 3F 4C EF 38 C4 ybàê.aÞ¶Iö¼?Lï8Ä
00000100 F3 55 04 E5 1E C1 12 DE 5C 38 4D F7 BA 0B 8D 57 óU.å.Á.Þ\8M÷º..W
00000110 8A 4C 70 2B 6B F1 1D 5F AC 00 00 00 00 ŠLp+kñ._¬....

Broken down it looks like this:

01000000 - version
0000000000000000000000000000000000000000000000000000000000000000 - prev block
3BA3EDFD7A7B12B27AC72C3E67768F617FC81BC3888A51323A9FB8AA4B1E5E4A - merkle root
29AB5F49 - timestamp
FFFF001D - bits
1DAC2B7C - nonce
01 - number of transactions
01000000 - version
01 - input
0000000000000000000000000000000000000000000000000000000000000000FFFFFFFF - prev output
4D - script length
04FFFF001D0104455468652054696D65732030332F4A616E2F32303039204368616E63656C6C6F72206F6E206272696E6B206F66207365636F6E64206261696C6F757420666F722062616E6B73 - scriptsig
FFFFFFFF - sequence
01 - outputs
00F2052A01000000 - 50 BTC
43 - pk_script length
4104678AFDB0FE5548271967F1A67130B7105CD6A828E03909A67962E0EA1F61DEB649F6BC3F4CEF38C4F35504E51EC112DE5C384DF7BA0B8D578A4C702B6BF11D5FAC - pk_script
00000000 - lock time

==Notes==
<references/>

[[zh-cn:创世block]]
[[es:Bloque Génesis]]

Talk:Mini private key format

2011-09-25T14:15:58Z

Willphase: Created page with "I'm not sure I like the idea of encouraging people to use less than the current 160bits of entropy in a private key. ~~~~"

I'm not sure I like the idea of encouraging people to use less than the current 160bits of entropy in a private key. [[User:Willphase|Willphase]] 14:15, 25 September 2011 (GMT)

Help:FAQ

2011-07-31T23:28:08Z

Willphase: add explanation of missing bitcoins - as seen on the forums a lot

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”).
A Bitcoin isn't tangible. It is just a number associated with a [[Address|Bitcoin Address]]. 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|trade them]] for traditional currency.
* Find a local trader on [http://tradebitcoin.com tradebitcoin] (or somewhere else) and trade with him in cash.
* Create a new [[block]] (currently yields 50 Bitcoins).
* Participate in a [[Pooled mining|mining pool]].

=== Can I buy Bitcoins with Paypal? ===

While it's possible to find an individual who wishes to sell Bitcoin to you via Paypal, (perhaps via [http://www.bitcoin-otc.com/ #bitcoin-otc] ) most major 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 goods. Paypal too often sides with the fraudulent buyer in this case, and so exchangers no longer allow this method of funding.

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

There are many forums ou there that are based on Bitcoins although the off-site active bitcoin forum would be http://bitforums.net. The other on-site forum is located on http://bitcoin.org

Buying Bitcoins from individuals with this method is still possible, but requires mutual trust. In this case, Bitcoin seller beware.

=== 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 inflation|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 coins will approach 21,000,000 BTC over time.

Blocks should be 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.

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

[http://blockexplorer.com/q/totalbc Current count]

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 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 accepted as payment by many. 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. In a sense, you could say that Bitcoin is "backed up" by the price tags of merchants – a price tag is a promise to exchange goods for a specified amount of currency.

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.

=== What if someone bought up all the existing Bitcoins? ===
What if somebody bought up all the gold in the world? Well, by attempting to buy it all, the buyer would just drive the prices up until he runs out of money.

Not all Bitcoins are for sale. Just as with gold, no one can buy a Bitcoin that isn't available for sale.

=== Won't Bitcoin's deflationary tendencies cause a deflationary spiral? ===
See the article [[Deflationary spiral]].

=== 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.

=== 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 profit from the usefulness of a stable and widely accepted p2p currency.

The fact that early adopters benefit more doesn't alone make anything a ponzi scheme. Apple stocks aren't ponzi even though the early investors got rich.

=== Is Bitcoin a bubble? ===
Yes, in the same way as the euro and dollar are. They only have value in exchange and no value in use. 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.

==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!

Why ten minutes specifically? It is a tradeoff chosen by Satoshi between propagation time of new blocks in large networks and the amount of work wasted due to chain splits. If that made no sense to you, don't worry. Reading [http://www.bitcoin.org/bitcoin.pdf the technical paper] should make things clearer.

=== Do you have to wait 10 minutes in order to buy or sell things with BitCoin? ===

No, it's reasonable to sell things without waiting for a confirmation as long as the transaction is not of high value.

When people ask this question they are usually thinking about applications like supermarkets or snack machines, as discussed in [http://www.bitcoin.org/smf/index.php?topic=423.msg3819#msg3819 this thread from July 2010]. Zero confirmation transactions still show up in the GUI, but you cannot spend them. You can however reason about the risk involved in assuming you ''will'' be able to spend them in future. In general, selling things that are fairly cheap (like snacks, digital downloads etc) for zero confirmations will not pose a problem if you are running a well connected node.

=== I 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. First of all, check the current max block count by going [http://blockexplorer.com/q/getblockcount here] and comparing that to the number in the bottom right hand corner of your client. If these numbers are different by more than 1 or 2 then you need to wait for your block chain to download. If not, 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://bitcoincharts.com/bitcoin/ 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 will take longer to transfer e.g. someone just sent you a coin, if you send that again, it will take a while to transfer unless you put a large (0.01) fee on it. 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.

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.

==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. Bitcoin will also try to connect to IRC (tcp port 6667) to meet other nodes to connect to.

If you want to restrict your firewall rules to a few ips and/or don't want to allow IRC connection, you can find stable nodes in the [[Fallback Nodes|fallback nodes list]]. If your provider blocks the common IRC ports, note that lfnet also listens on port 7777. Connecting to this alternate port currently requires either recompiling Bitcoin, or changing routing rules. For example, on Linux you can evade a port 6667 block by doing something like this:

echo 173.246.103.92 irc.lfnet.org >> /etc/hosts
iptables -t nat -A OUTPUT -p tcp --dest 173.246.103.92 --dport 6667 -j DNAT --to-destination :7777 -m comment --comment "bitcoind irc connection"

=== How does the peer finding mechanism work? ===
Bitcoin finds peers primarily by connecting to an IRC server (channel #bitcoin on irc.lfnet.org). If a connection to the IRC server cannot be established (like when connecting through TOR), an in-built node list will be used and the nodes will be queried for more node addresses.

==Mining==
===What is mining?===
Mining is the process of spending computation power to find valid blocks and thus create new Bitcoins.

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 50 newly generated Bitcoins. 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.

===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 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.

===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 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.

==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

==See Also==

* [[Man page]]
* [[Introduction]]

[[de:FAQ]]
[[zh-cn:FAQ]]
[[fr:FAQ]]

[[Category:Technical]]
[[Category:Vocabulary]]

Bitcoin Wallet Balance

2011-06-27T23:25:35Z

Willphase: Created page with "An Android App to allow you to view the balance in your wallet on your Android device. It works by reading your public key hashes (addresses) and obtaining your transactions fro..."

An Android App to allow you to view the balance in your wallet on your Android device. It works by reading your public key hashes (addresses) and obtaining your transactions from blockexplorer.com. Keys are exported once, saved in cloud storage, and allow the user to view their balance in real time on their device. The code is open sourced so it can be freely inspected (since it has to touch the wallet.dat)

This app was announced on June 24, 2011<ref>[http://forum.bitcoin.org/index.php?topic=21969.0 Android wallet balance viewer]</ref>.

==External Links==

* [http://code.google.com/p/bitcoinwallet/ homepage] on Google code hosting.

==References==
<references />

[[Category:Mobile]]

Software

2011-06-27T23:21:38Z

Willphase: add bitcoin wallet balance to mobile apps

List of Bitcoin-related software. See also [[:Category:Software|Category:Software]].

==Bitcoin clients==
Bitcoin clients:
*[[Original Bitcoin client|Bitcoin client]] - standard Bitcoin client, recommended for installation
*[[bitcoind]] - GUI-less version of the standard Bitcoin client, providing [[API reference (JSON-RPC)|JSON-RPC]] interface (see also -server option of the standard client)
Frontends to bitcoind:
*[[BitcoinApp]] - RPC client for iOS devices (iPhone, iPad, iPodTouch)
*[[Bitcoiner]] - Java RPC client (Android)
*[[Bitcoin-js-remote]] - JavaScript RPC client, support for QR codes
*[[Python Bitcoinclient]] - Python RPC client
*[[Spesmilo]] - Python/PySide RPC client
*[[Bitcoin-python]] - Python API
*[[Java Bitcoin Client]] - Java API
Alternative, experimental implementations:
*[[BitDroid]] - Java client
*[[Bitdollar]] - C++/Qt client, unstable beta version
*[[BitCoinJ]] - Java client by Google, early development stage
*[[Freecoin]] - C++ client, supports alternative currencies like [[Beertoken]]
*[[Pycoin]] - Python client
*[[QBitcoin]] - C++/Qt client, unfinished

==Bitcoin software==

Web interfaces for merchants:
*[[MyBitcoin]] - Buy Now button to insert on websites
*[[Btceconomy]] - a JavaScript widget listing items for sale
*[[Javascript Bitcoin Converter]] - currency conversion

Web apps (opensource):
*[[Bitcoin Central]] - currency exchange
*[[Bitcoin Poker Room]] - poker site

Browser extensions:
*[[Bitcoin Extension]] - check balance and send bitcoins (Chrome)
*[[Bitcoin Ticker]] - monitoring price (Chrome)
*[[Bitcoin Prices (extension)]] - monitoring price (Firefox)
*[[Bitcoin Tool]] - recognizes Bitcoin addresses on websites (Firefox, Chrome, IE)

PC apps:
*[[BTConvert]] - currency conversion
*[[Sierra Chart MtGox Bridge]] - real-time charting
*[[BitTicker]] - monitoring price (Mac OS X)
*[[ToyTrader]] - a command line trading tool for [[MtGox]]

Mobile apps:
*[[Bitcoin Alert]] - monitoring price (Android)
*[[BitcoinX]] - monitoring price (Android)
*[[BtcMobile]] - monitoring price and mining pool statistics (iPhone/iPad, Android)
*[[Miner Status]] - monitoring miner status (Android)
*[[SMS Bitcoins]] - transactions by SMS
*[[Bitcoin Wallet Balance]] - view your balance in real time on your android phone

Other device apps:
*[[Zen Cart Bitcoin Payment Module]] - a payment module that interacts with bitcoind for the Zen Cart eCommerce shopping chart

Operating systems:
*[[LinuxCoin]] - a lightweight Debian-based OS, with the Bitcoin client and GPU mining software

Mining apps:
*[[Poclbm]] - Python/OpenCL GPU miner ([[Poclbm-gui|GUI]])
*[[Poclbm-mod]] - more efficient version of [[Poclbm]] ([[Poclbm-mod-gui|GUI]])
*[[DiabloMiner]] - Java/OpenCL GPU miner ([[DiabloMiner.app|MAC OS X GUI]])
*[[RPC Miner]] - remote RPC miner ([[RPCminer.app|MAC OS X GUI]])
*[[Phoenix miner]] - miner
*[[Cpu Miner]] - miner
*[[Ufasoft miner]] - miner
*[[Pyminer]] - Python miner, reference implementation
*[[Remote miner]] - mining pool software
*[[Poold]] - mining pool software
*[[Open Source FGPA Bitcoin Miner]] - a miner that makes use of an FPGA Board

Utilities, libraries, and interfaces:
*[[Bitcointools]] - a set of Python tools accessing the transaction database and the wallet
*[[Finance::MtGox]] - a Perl module which interfaces with the Mt. Gox API
*[[BitcoinCrypto]] - a lightweight Bitcoin crypto library for Java/Android
*[[Bitcoin Dissector]] - a wireshark dissector for the bitcoin protocol

Lists of software:
*[[BitGit]] - list of Bitcoin-related opensource projects hosted at Git

Developer resources:
*[[:Category:Developer|Category:Developer]]
*[[:Category:Technical|Category:Technical]]
*[[Original Bitcoin client/API calls list]]
*[[API reference (JSON-RPC)]]

Other:
*[[Namecoin]] - a distributed naming system based on Bitcoin technology
*[[Bitcoin Consultancy]] - an organization providing open source software and Bitcoin-related consulting
*[[Open Transactions]] - a financial crypto and digital cash software library, complementary to Bitcoin
*[[Moneychanger]] - Java-based GUI for [[Open Transactions]]