Bitcoin Wiki - User contributions [en]

Offline transactions

2019-12-11T07:21:43Z

Priem19: Replaces dead link with internal reference. Adds [sic] to sentence in need of correcting.

The term "offline transaction" refers to the practice of keeping the private keys on an offline device (not connected to the internet), and signing on individuals transactions. The signature is then copy-pasted from this device into a connected device, and broadcast into the Bitcoin network.

Assuming the offline computer is malware-free is [''sic''] easier than a connected device. If this assumption is held, then this practice is virtually risk-free of bitcoin theft.

Offline transactions can also be used when talking to an [[Overlay Network]] (e.g. [[Stratum]]) or equivalent - an ultra thin client can send only signatures to the Overlay server, thus mitigating the risk of a malicious server running away with one's BTC.

Help:Introduction

2019-12-03T10:00:26Z

Priem19: /* Currency */ Changes external link to internal.

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 [[Alpaca|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 [https://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, or their balance partially or wholly confiscated.
* Banks and other payment processors like PayPal, Visa, and Mastercard may refuse to process payments for certain 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 for a solution to a very difficult math problem the difficulty of which is precisely known. This difficulty is automatically adjusted on a predictable schedule so that the number of solutions found globally for a given unit of time is constant: the global system aims for 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]]". The solution itself is a [[Proof of work| proof-of-work]] or PoW. It is hard to find, but easy to verify.

Blocks create 12.5 new bitcoins at present [October 2016]. 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%. Originally the block reward was 50 bitcoins; it halved in November 2012; it then halved again in July 2016. 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 to Alice.
* Alice adds Bob’s address and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Alice signs the transaction with her private key, and announces her public key for signature verification.
* 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 address and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Bob signs the transaction with his private key, and announces his public key for signature verification.
* 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 address with her address, 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:

:1PHYrmdJ22MKbJevpb3MBNpVckjZHt89hz

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 [https://btc.com/ BTC.com], [https://www.biteasy.com/ Biteasy.com], [https://blockchain.info/ Blockchain.info], [http://btc.blockr.io/ Blokr.io Bitcoin Block Explorer] or [https://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.

*In October 2014, according to [https://www.coindesk.com/state-of-bitcoin-q3-2014-report-maturing-ecosystem-price-pressure/ Coindesk report] there were more than 7.5 million bitcoin wallets.

*In October 2016, according to [https://Blockchain.info blockchain.info] user counts based on Blockchain wallet, there are about 8.8 mln registered Bitcoin users on its platform. [https://cointelegraph.com/news/counting-them-all-how-to-figure-out-actual-number-of-bitcoin-users Cointelegraph report]

*According to [https://blockchain.info/charts/my-wallet-n-users blockchain.info], from October 2016 till January 2018 the Bitcoin user base has almost tripled for total of 22 million users.

==See Also==
* [http://bitcoinhelp.net Bitcoin Help] — the simple guide to Bitcoin.
* Learn the entire history of Bitcoin in the interactive timeline at [http://historyofbitcoin.org History of Bitcoin].
* [https://www.weusecoins.com What Is Bitcoin?]
* [https://www.bitcoinmining.com What Is Bitcoin Mining?]

[[zh-cn:简介]]

[[de:Einführung]]
[[fr:Introduction]]

User:Priem19

2019-12-03T09:51:46Z

Priem19: Profile.

https://www.quitfacebook.org

Changelog

2019-12-03T09:47:57Z

Priem19: /* 0.6.30.6.3 release announcement */ Typo.

This page aggregates the changelogs that have been posted on the forum for the Bitcoin releases.
Note that some download links are not longer valid as highly insecure versions may have been deleted, or links may have changed.

This page hasn't been updated for a while. Changelogs for newer versions as well as historical release notes can be found at bitcoin.org: https://bitcoin.org/en/version-history and/or through github: https://github.com/bitcoin/bitcoin/tree/master/doc/release-notes

=Changelogs=

https://bitcoin.org/en/release/v0.7.1
==0.7.X==

===0.7.1<ref>[https://bitcoin.org/en/release/v0.7.1 0.7.1 release announcement]</ref>===

New features:

* Added a boolean argument to the RPC stop command, if true sets -detachdb to create standalone database .dat files before shutting down.

* -salvagewallet command-line option, which moves any existing wallet.dat to wallet.{timestamp}.dat and then attempts to salvage public/private keys and master encryption keys (if the wallet is encrypted) into a new wallet.dat. This should only be used if your wallet becomes corrupted, and is not intended to replace regular wallet backups.

* Import $DataDir/bootstrap.dat automatically, if it exists.

==0.6.X==
After 0.6.3, all subsequent releases are stable maintenance releases, 0.7.0 is based on 0.6.3.

===0.6.3<ref>[https://bitcointalk.org/index.php?topic=89877.0 0.6.3 release announcement]</ref>===
Bitcoin version 0.6.3 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.6.3/

This is a bug-fix release, with no new features.

Please report bugs using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

CHANGE SUMMARY

Fixed a serious denial-of-service attack that could cause the
bitcoin process to become unresponsive. Thanks to Sergio Lerner
for finding and responsibly reporting the problem. (CVE-2012-3789)

Optimized the process of checking transaction signatures, to
speed up processing of new block messages and make propagating
blocks across the network faster.

Fixed an obscure bug that could cause the bitcoin process to get
stuck on an invalid block-chain, if the invalid chain was
hundreds of blocks long.

Bitcoin-Qt no longer automatically selects the first address
in the address book (Issue #1384).

Fixed minimize-to-dock behavior of Bitcoin-Qt on the Mac.

Added a block checkpoint at block 185,333 to speed up initial
blockchain download.

===0.6.2<ref>[https://bitcointalk.org/index.php?topic=80187.0 0.6.2 release announcement]</ref>===
Bitcoin version 0.6.2 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.6.2/

This is a bug-fix and code-cleanup release, with no major new features.

Please report bugs using the github issue tracker at:
https://github.com/bitcoin/bitcoin/issues

NOTABLE CHANGES

Much faster shutdowns. However, the blkindex.dat file is no longer
portable to different data directories by default. If you need a
portable blkindex.dat file then run with the new -detachdb=1 option
or the "Detach databases at shutdown" GUI preference.

Fixed https://github.com/bitcoin/bitcoin/issues/1065, a bug that
could cause long-running nodes to crash.

Mac and Windows binaries are compiled against OpenSSL 1.0.1b (Linux
binaries are dynamically linked to the version of OpenSSL on the system).

CHANGE SUMMARY

Use 'git shortlog --no-merges v0.6.0..' for a summary of this release.

Source codebase changes:
- Many source code cleanups and warnings fixes. Close to building with -Wall
- Locking overhaul, and several minor locking fixes
- Several source code portability fixes, e.g. FreeBSD

JSON-RPC interface changes:
- addmultisigaddress enabled for mainnet (previously only enabled for testnet)

Network protocol changes:
- protocol version 60001
- added nonce value to "ping" message (BIP 31)
- added new "pong" message (BIP 31)

Backend storage changes:
- Less redundant database flushing, especially during initial block download
- Shutdown improvements (see above)

Qt user interface:
- minor URI handling improvements
- progressbar improvements
- error handling improvements (show message box rather than console exception,
etc.)
- by popular request, make 4th bar of connection icon green

===0.6.1===
Never released

===0.6.0<ref>[https://bitcointalk.org/index.php?topic=74737.0 0.6.0 release announcement]</ref>===
Bitcoin version 0.6.0 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.6.0/test/

This release includes more than 20 language localizations.
More translations are welcome; join the
project at Transifex to help:
https://www.transifex.net/projects/p/bitcoin/

Please report bugs using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

Project source code is hosted at github; we are no longer
distributing .tar.gz files here, you can get them
directly from github:
https://github.com/bitcoin/bitcoin/tarball/v0.6.0 # .tar.gz
https://github.com/bitcoin/bitcoin/zipball/v0.6.0 # .zip

For Ubuntu users, there is a ppa maintained by Matt Corallo which
you can add to your system so that it will automatically keep
bitcoin up-to-date. Just type
sudo apt-add-repository ppa:bitcoin/bitcoin
in your terminal, then install the bitcoin-qt package.

KNOWN ISSUES

Shutting down while synchronizing with the network
(downloading the blockchain) can take more than a minute,
because database writes are queued to speed up download
time.

NEW FEATURES SINCE BITCOIN VERSION 0.5

Initial network synchronization should be much faster
(one or two hours on a typical machine instead of ten or more
hours).

Backup Wallet menu option.

Bitcoin-Qt can display and save QR codes for sending
and receiving addresses.

New context menu on addresses to copy/edit/delete them.

New Sign Message dialog that allows you to prove that you
own a bitcoin address by creating a digital
signature.

New wallets created with this version will
use 33-byte 'compressed' public keys instead of
65-byte public keys, resulting in smaller
transactions and less traffic on the bitcoin
network. The shorter keys are already supported
by the network but wallet.dat files containing
short keys are not compatible with earlier
versions of Bitcoin-Qt/bitcoind.

New command-line argument -blocknotify=<command>
that will spawn a shell process to run <command>
when a new block is accepted.

New command-line argument -splash=0 to disable
Bitcoin-Qt's initial splash screen

validateaddress JSON-RPC api command output includes
two new fields for addresses in the wallet:
pubkey : hexadecimal public key
iscompressed : true if pubkey is a short 33-byte key

New JSON-RPC api commands for dumping/importing
private keys from the wallet (dumprivkey, importprivkey).

New JSON-RPC api command for getting information about
blocks (getblock, getblockhash).

New JSON-RPC api command (getmininginfo) for getting
extra information related to mining. The getinfo
JSON-RPC command no longer includes mining-related
information (generate/genproclimit/hashespersec).

NOTABLE CHANGES

BIP30 implemented (security fix for an attack involving
duplicate "coinbase transactions").

The -nolisten, -noupnp and -nodnsseed command-line
options were renamed to -listen, -upnp and -dnsseed,
with a default value of 1. The old names are still
supported for compatibility (so specifying -nolisten
is automatically interpreted as -listen=0; every
boolean argument can now be specified as either
-foo or -nofoo).

The -noirc command-line options was renamed to
-irc, with a default value of 0. Run -irc=1 to
get the old behavior.

Three fill-up-available-memory denial-of-service
attacks were fixed.

NOT YET IMPLEMENTED FEATURES

Support for clicking on bitcoin: URIs and
opening/launching Bitcoin-Qt is available only on Linux,
and only if you configure your desktop to launch
Bitcoin-Qt. All platforms support dragging and dropping
bitcoin: URIs onto the Bitcoin-Qt window to start
payment.

PRELIMINARY SUPPORT FOR MULTISIGNATURE TRANSACTIONS

This release has preliminary support for multisignature
transactions-- transactions that require authorization
from more than one person or device before they
will be accepted by the bitcoin network.

Prior to this release, multisignature transactions
were considered 'non-standard' and were ignored;
with this release multisignature transactions are
considered standard and will start to be relayed
and accepted into blocks.

It is expected that future releases of Bitcoin-Qt
will support the creation of multisignature transactions,
once enough of the network has upgraded so relaying
and validating them is robust.

For this release, creation and testing of multisignature
transactions is limited to the bitcoin test network using
the "addmultisigaddress" JSON-RPC api call.

Short multisignature address support is included in this
release, as specified in BIP 13 and BIP 16.

==0.5.X==
After 0.5.1, all subsequent releases are stable maintenance releases, 0.6.0 is based on 0.5.1.

===0.5.5<ref>[https://bitcointalk.org/index.php?topic=79651 0.4.6/0.5.5 release announcement]</ref>===
bitcoind and Bitcoin-Qt version 0.5.5 are now available for download at:
Windows: installer | zip (sig)
Source: tar.gz
bitcoind and Bitcoin-Qt version 0.6.0.7 are also tagged in git, but it is recommended to upgrade to 0.6.1.

These are bugfix-only releases.

Please report bugs by replying to this forum thread. Note that the 0.4.x wxBitcoin GUI client is no longer maintained nor supported. If someone would like to step up to maintain this, they should contact Luke-Jr.

BUG FIXES

Version 0.6.0 allowed importing invalid "private keys", which would be unspendable; 0.6.0.7 will now verify the private key is valid, and refuse to import an invalid one
Verify status of encrypt/decrypt calls to detect failed padding
Check blocks for duplicate transactions earlier. Fixes #1167
Upgrade Windows builds to OpenSSL 1.0.1b
Set label when selecting an address that already has a label. Fixes #1080 (Bitcoin-Qt)
JSON-RPC listtransactions's from/count handling is now fixed
Optimize and fix multithreaded access, when checking whether we already know about transactions
Fix potential networking deadlock
Proper support for Growl 1.3 notifications
Display an error, rather than crashing, if encoding a QR Code failed (0.6.0.7)
Don't erroneously set "Display addresses" for users who haven't explicitly enabled it (Bitcoin-Qt)
Some non-ASCII input in JSON-RPC expecting hexadecimal may have been misinterpreted rather than rejected
Missing error condition checking added
Do not show green tick unless all known blocks are downloaded. Fixes #921 (Bitcoin-Qt)
Increase time ago of last block for "up to date" status from 30 to 90 minutes
Show a message box when runaway exception happens (Bitcoin-Qt)
Use a messagebox to display the error when -server is provided without providing a rpc password
Show error message instead of exception crash when unable to bind RPC port (Bitcoin-Qt)
Correct sign message bitcoin address tooltip. Fixes #1050 (Bitcoin-Qt)
Removed "(no label)" from QR Code dialog titlebar if we have no label (0.6.0.7)
Removed an ugly line break in tooltip for mature transactions (0.6.0.7)
Add missing tooltip and key shortcut in settings dialog (part of #1088) (Bitcoin-Qt)
Work around issue in boost::program_options that prevents from compiling in clang
Fixed bugs occurring only on platforms with unsigned characters (such as ARM).
Rename make_windows_icon.py to .sh as it is a shell script. Fixes #1099 (Bitcoin-Qt)
Various trivial internal corrections to types used for counting/size loops and warnings

===0.5.4<ref>[https://bitcointalk.org/index.php?topic=76808.0 0.5.4 release announcement]</ref>===
Bitcoin version 0.5.4 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.5.4/
NOTE: 0.5.4rc3 is being renamed to 0.5.4 final with no changes.

This is a bugfix-only release in the 0.5.x series, plus a few protocol updates.

Please report bugs using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

Stable source code is hosted at Gitorious:
http://gitorious.org/bitcoin/bitcoind-stable/archive-tarball/v0.5.4#.tar.gz

PROTOCOL UPDATES

BIP 16: Special-case "pay to script hash" logic to enable minimal validation of new transactions.
Support for validating message signatures produced with compressed public keys.

BUG FIXES

Build with thread-safe MingW libraries for Windows, fixing a dangerous memory corruption scenario when exceptions are thrown.
Fix broken testnet mining.
Stop excess inventory relay during initial block download.
When disconnecting a node, clear the received buffer so that we do not process any already received messages.
Yet another attempt at implementing "minimize to tray" that works on all operating systems.
Fix Bitcoin-Qt notifications under Growl 1.3.
Increase required age of Bitcoin-Qt's "not up to date" status from 30 to 90 minutes.
Implemented missing verifications that led to crash on entering some wrong passphrases for encrypted wallets.
Fix default filename suffixes in GNOME save dialog.
Make the "Send coins" tab use the configured unit type, even on the first attempt.
Print detailed wallet loading errors to debug.log when it is corrupt.
Allocate exactly the amount of space needed for signing transactions, instead of a fixed 10k buffer.
Workaround for improbable memory access violation.
Check wallet's minimum version before trying to load it.
Remove wxBitcoin properly when installing Bitcoin-Qt over it. (Windows)
Detail reorganization information better in debug log.
Use a messagebox to display the error when -server is provided without configuring a RPC password.
Testing suite build now honours provided CXXFLAGS.
Removed an extraneous line-break in mature transaction tooltips.
Fix some grammatical errors in translation process documentation.

===0.5.3<ref>[https://bitcointalk.org/index.php?topic=68895.0 0.5.3 release announcement]</ref>===
Bitcoin version 0.5.3 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.5.3/

This is a bugfix-only release based on 0.5.1.
It also includes a few protocol updates.

Please report bugs using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

Stable source code is hosted at Gitorious:
http://gitorious.org/bitcoin/bitcoind-stable/archive-tarball/v0.5.3#.tar.gz

PROTOCOL UPDATES

BIP 30: Introduce a new network rule: "a block is not valid if it contains a transaction whose hash already exists in the block chain, unless all that transaction's outputs were already spent before said block" beginning on March 15, 2012, 00:00 UTC.
On testnet, allow mining of min-difficulty blocks if 20 minutes have gone by without mining a regular-difficulty block. This is to make testing Bitcoin easier, and will not affect normal mode.

BUG FIXES

Limit the number of orphan transactions stored in memory, to prevent a potential denial-of-service attack by flooding orphan transactions. Also never store invalid transactions at all.
Fix possible buffer overflow on systems with very long application data paths. This is not exploitable.
Resolved multiple bugs preventing long-term unlocking of encrypted wallets
(issue #922).
Only send local IP in "version" messages if it is globally routable (ie, not private), and try to get such an IP from UPnP if applicable.
Reannounce UPnP port forwards every 20 minutes, to workaround routers expiring old entries, and allow the -upnp option to override any stored setting.
Skip splash screen when -min is used, and fix Minimize to Tray function.
Do not blank "label" in Bitcoin-Qt "Send" tab, if the user has already entered something.
Correct various labels and messages.
Various memory leaks and potential null pointer deferences have been fixed.
Handle invalid Bitcoin URIs using "bitcoin://" instead of "bitcoin:".
Several shutdown issues have been fixed.
Revert to "global progress indication", as starting from zero every time was considered too confusing for many users.
Check that keys stored in the wallet are valid at startup, and if not, report corruption.
Enable accessible widgets on Windows, so that people with screen readers such as NVDA can make sense of it.
Various build fixes.
If no password is specified to bitcoind, recommend a secure password.
Automatically focus and scroll to new "Send coins" entries in Bitcoin-Qt.
Show a message box for --help on Windows, for Bitcoin-Qt.
Add missing "About Qt" menu option to show built-in Qt About dialog.
Don't show "-daemon" as an option for Bitcoin-Qt, since it isn't available.
Update hard-coded fallback seed nodes, choosing recent ones with long uptime and versions at least 0.4.0.
Add checkpoint at block 168,000.

===0.5.2<ref>[https://bitcointalk.org/index.php?topic=60146.0 0.5.2 release announcement]</ref>===
Bitcoin version 0.5.2 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.5.2/

This is a bugfix-only release based on 0.5.1.

Please report bugs using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

Stable source code is hosted at Gitorious:
http://gitorious.org/bitcoin/bitcoind-stable/archive-tarball/v0.5.2#.tar.gz

BUG FIXES

Check all transactions in blocks after the last checkpoint (0.5.0 and 0.5.1 skipped checking ECDSA signatures during initial blockchain download).
Cease locking memory used by non-sensitive information (this caused a huge performance hit on some platforms, especially noticable during initial blockchain download; this was
not a security vulnerability).
Fixed some address-handling deadlocks (client freezes).
No longer accept inbound connections over the internet when Bitcoin is being used with Tor (identity leak).
Re-enable SSL support for the JSON-RPC interface (it was unintentionally disabled for the 0.5.0 and 0.5.1 release Linux binaries).
Use the correct base transaction fee of 0.0005 BTC for accepting transactions into mined blocks (since 0.4.0, it was incorrectly accepting 0.0001 BTC which was only meant to be relayed).
Don't show "IP" for transactions which are not necessarily IP transactions.
Add new DNS seeds (maintained by Pieter Wuille and Luke Dashjr).

===0.5.1<ref>[https://bitcointalk.org/index.php?topic=54717.0 0.5.1 release announcement]</ref>===
Bitcoin version 0.5.1 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.5.1/

This is a bugfix-only release.

This release includes 13 translations, including 5 new translations:
Italian, Hungarian, Ukranian, Portuguese (Brazilian) and Simplified Chinese.
More translations are welcome; join the project at Transifex if you can help:
https://www.transifex.net/projects/p/bitcoin/

Please report bugs using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

Project source code is hosted at github; we are no longer
distributing .tar.gz files here, you can get them
directly from github:
https://github.com/bitcoin/bitcoin/tarball/v0.5.1 # .tar.gz
https://github.com/bitcoin/bitcoin/zipball/v0.5.1 # .zip

For Ubuntu users, there is a new ppa maintained by Matt Corallo which
you can add to your system so that it will automatically keep
bitcoin up-to-date. Just type
sudo apt-add-repository ppa:bitcoin/bitcoin
in your terminal, then install the bitcoin-qt package.

BUG FIXES

Re-enable SSL support for the JSON-RPC interface (it was unintentionally
disabled for the 0.5.0 release binaries).

The code that finds peers via "dns seeds" no longer stops bitcoin startup
if one of the dns seed machines is down.

Tooltips on the transaction list view were rendering incorrectly (as black boxes
or with a transparent background).

Prevent a denial-of-service attack involving flooding a bitcoin node with
orphan blocks.

The wallet passphrase dialog now warns you if the caps lock key was pressed.

Improved searching in addresses and labels in bitcoin-qt.

===0.5.0<ref>[https://bitcointalk.org/index.php?topic=52480.0 0.5.0 release announcement]</ref>===
Bitcoin version 0.5.0 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.5.0/

The major change for this release is a completely new graphical interface that uses the Qt user interface toolkit.

This release include German, Spanish, Spanish-Castilian, Norwegian and Dutch translations. More translations are welcome; join the project at Transifex if you can help:
https://www.transifex.net/projects/p/bitcoin/

Please report bugs using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

For Ubuntu users, there is a new ppa maintained by Matt Corallo which you can add to your system so that it will automatically keep bitcoin up-to-date. Just type "sudo apt-add-repository ppa:bitcoin/bitcoin" in your terminal, then install the bitcoin-qt package.

MAJOR BUG FIX (CVE-2011-4447)

The wallet encryption feature introduced in Bitcoin version 0.4.0 did not sufficiently secure the private keys. An attacker who
managed to get a copy of your encrypted wallet.dat file might be able to recover some or all of the unencrypted keys and steal the
associated coins.

If you have a previously encrypted wallet.dat, the first time you run bitcoin-qt or bitcoind the wallet will be rewritten, Bitcoin will
shut down, and you will be prompted to restart it to run with the new, properly encrypted file.

If you had a previously encrypted wallet.dat that might have been copied or stolen (for example, you backed it up to a public
location) you should send all of your bitcoins to yourself using a new bitcoin address and stop using any previously generated addresses.

Wallets encrypted with this version of Bitcoin are written properly.

Technical note: the encrypted wallet's 'keypool' will be regenerated the first time you request a new bitcoin address; to be certain that the
new private keys are properly backed up you should:

1. Run Bitcoin and let it rewrite the wallet.dat file

2. Run it again, then ask it for a new bitcoin address.
Bitcoin-Qt: Address Book, then New Address...
bitcoind: run the 'walletpassphrase' RPC command to unlock the wallet, then run the 'getnewaddress' RPC command.

3. If your encrypted wallet.dat may have been copied or stolen, send all of your bitcoins to the new bitcoin address.

4. Shut down Bitcoin, then backup the wallet.dat file.
IMPORTANT: be sure to request a new bitcoin address before backing up, so that the 'keypool' is regenerated and backed up.

"Security in depth" is always a good idea, so choosing a secure location for the backup and/or encrypting the backup before uploading it is recommended. And as in previous releases, if your machine is infected by malware there are several ways an attacker might steal your bitcoins.

Thanks to Alan Reiner (etotheipi) for finding and reporting this bug.

MAJOR GUI CHANGES

"Splash" graphics at startup that show address/wallet/blockchain loading progress.

"Synchronizing with network" progress bar to show block-chain download progress.

Icons at the bottom of the window that show how well connected you are to the network, with tooltips to display details.

Drag and drop support for bitcoin: URIs on web pages.

Export transactions as a .csv file.

Many other GUI improvements, large and small.

RPC CHANGES

getmemorypool : new RPC command, provides everything needed to construct a block with a custom generation transaction and submit a solution

listsinceblock : new RPC command, list transactions since given block

signmessage/verifymessage : new RPC commands to sign a message with one of your private keys or verify that a message signed by the private key associated with a bitcoin address.

GENERAL CHANGES

Faster initial block download.

==0.4.X==
After 0.4.0, all subsequent releases are stable maintenance releases, 0.5.0 is based on 0.4.0.

===0.4.6<ref>[https://bitcointalk.org/index.php?topic=79651 0.4.6/0.5.5 release announcement]</ref>===
bitcoind version 0.4.6 is now available for download at:
Windows: installer | zip (sig)
Source: tar.gz
bitcoind and Bitcoin-Qt version 0.6.0.7 are also tagged in git, but it is recommended to upgrade to 0.6.1.

These are bugfix-only releases.

Please report bugs by replying to this forum thread. Note that the 0.4.x wxBitcoin GUI client is no longer maintained nor supported. If someone would like to step up to maintain this, they should contact Luke-Jr.

BUG FIXES

Version 0.6.0 allowed importing invalid "private keys", which would be unspendable; 0.6.0.7 will now verify the private key is valid, and refuse to import an invalid one
Verify status of encrypt/decrypt calls to detect failed padding
Check blocks for duplicate transactions earlier. Fixes #1167
Upgrade Windows builds to OpenSSL 1.0.1b
Set label when selecting an address that already has a label. Fixes #1080 (Bitcoin-Qt)
JSON-RPC listtransactions's from/count handling is now fixed
Optimize and fix multithreaded access, when checking whether we already know about transactions
Fix potential networking deadlock
Proper support for Growl 1.3 notifications
Display an error, rather than crashing, if encoding a QR Code failed (0.6.0.7)
Don't erroneously set "Display addresses" for users who haven't explicitly enabled it (Bitcoin-Qt)
Some non-ASCII input in JSON-RPC expecting hexadecimal may have been misinterpreted rather than rejected
Missing error condition checking added
Do not show green tick unless all known blocks are downloaded. Fixes #921 (Bitcoin-Qt)
Increase time ago of last block for "up to date" status from 30 to 90 minutes
Show a message box when runaway exception happens (Bitcoin-Qt)
Use a messagebox to display the error when -server is provided without providing a rpc password
Show error message instead of exception crash when unable to bind RPC port (Bitcoin-Qt)
Correct sign message bitcoin address tooltip. Fixes #1050 (Bitcoin-Qt)
Removed "(no label)" from QR Code dialog titlebar if we have no label (0.6.0.7)
Removed an ugly line break in tooltip for mature transactions (0.6.0.7)
Add missing tooltip and key shortcut in settings dialog (part of #1088) (Bitcoin-Qt)
Work around issue in boost::program_options that prevents from compiling in clang
Fixed bugs occurring only on platforms with unsigned characters (such as ARM).
Rename make_windows_icon.py to .sh as it is a shell script. Fixes #1099 (Bitcoin-Qt)
Various trivial internal corrections to types used for counting/size loops and warnings

===0.4.5===
(No known forum post.)

===0.4.4<ref>[https://bitcointalk.org/index.php?topic=70566.0 0.4.4 release announcement]</ref>===
Bitcoin version 0.4.4 is now available for download at:
http://luke.dashjr.org/programs/bitcoin/files/bitcoind-0.4.4/

This is a bugfix-only release based on 0.4.0.

Please note that the wxBitcoin GUI client is no longer maintained nor supported. If someone would like to step up to maintain this, they should contact Luke-Jr.

Please report bugs for the daemon only using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

Stable source code is hosted at Gitorious:
http://gitorious.org/bitcoin/bitcoind-stable/archive-tarball/v0.4.4#.tar.gz

BUG FIXES

Limit the number of orphan transactions stored in memory, to prevent a potential denial-of-service attack by flooding orphan transactions. Also never store invalid transactions at all.
Fix possible buffer overflow on systems with very long application data paths. This is not exploitable.
Resolved multiple bugs preventing long-term unlocking of encrypted wallets (issue #922).
Only send local IP in "version" messages if it is globally routable (ie, not private), and try to get such an IP from UPnP if applicable.
Reannounce UPnP port forwards every 20 minutes, to workaround routers expiring old entries, and allow the -upnp option to override any stored setting.
Various memory leaks and potential null pointer deferences have been
fixed.
Several shutdown issues have been fixed.
Check that keys stored in the wallet are valid at startup, and if not,
report corruption.
Various build fixes.
If no password is specified to bitcoind, recommend a secure password.
Update hard-coded fallback seed nodes, choosing recent ones with long uptime and versions at least 0.4.0.
Add checkpoint at block 168,000.

===0.4.3<ref>[https://bitcointalk.org/index.php?topic=57734.0 0.4.3 release announcement]</ref>===
bitcoind version 0.4.3 is now available for download at:
http://luke.dashjr.org/programs/bitcoin/files/bitcoind-0.4.3/ (until Gavin uploads to SourceForge)

This is a bugfix-only release based on 0.4.0.

Please note that the wxBitcoin GUI client is no longer maintained nor supported. If someone would like to step up to maintain this, they should contact Luke-Jr.

Please report bugs for the daemon only using the issue tracker at github:
https://github.com/bitcoin/bitcoin/issues

Stable source code is hosted at Gitorious:
http://gitorious.org/bitcoin/bitcoind-stable/archive-tarball/v0.4.3#.tar.gz

BUG FIXES

Cease locking memory used by non-sensitive information (this caused a huge performance hit on some platforms, especially noticable during initial blockchain download).
Fixed some address-handling deadlocks (client freezes).
No longer accept inbound connections over the internet when Bitcoin is being used with Tor (identity leak).
Use the correct base transaction fee of 0.0005 BTC for accepting transactions into mined blocks (since 0.4.0, it was incorrectly accepting 0.0001 BTC which was only meant to be relayed).
Add new DNS seeds (maintained by Pieter Wuille and Luke Dashjr).

===0.4.2===
(No known forum post.)

===0.4.1<ref>[https://bitcointalk.org/index.php?topic=52503.0 0.4.1 release announcement]</ref>===
Bitcoin version 0.4.1 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.4.1/

This is a bugfix only release based on 0.4.0.

Please report bugs by replying to this forum thread.

MAJOR BUG FIX (CVE-2011-4447)

The wallet encryption feature introduced in Bitcoin version 0.4.0 did not sufficiently secure the private keys. An attacker who
managed to get a copy of your encrypted wallet.dat file might be able to recover some or all of the unencrypted keys and steal the
associated coins.

If you have a previously encrypted wallet.dat, the first time you run wxbitcoin or bitcoind the wallet will be rewritten, Bitcoin will
shut down, and you will be prompted to restart it to run with the new, properly encrypted file.

If you had a previously encrypted wallet.dat that might have been copied or stolen (for example, you backed it up to a public
location) you should send all of your bitcoins to yourself using a new bitcoin address and stop using any previously generated addresses.

Wallets encrypted with this version of Bitcoin are written properly.

Technical note: the encrypted wallet's 'keypool' will be regenerated the first time you request a new bitcoin address; to be certain that the
new private keys are properly backed up you should:

1. Run Bitcoin and let it rewrite the wallet.dat file

2. Run it again, then ask it for a new bitcoin address.
wxBitcoin: new address visible on main window
bitcoind: run the 'walletpassphrase' RPC command to unlock the wallet, then run the 'getnewaddress' RPC command.

3. If your encrypted wallet.dat may have been copied or stolen, send all of your bitcoins to the new bitcoin address.

4. Shut down Bitcoin, then backup the wallet.dat file.
IMPORTANT: be sure to request a new bitcoin address before backing up, so that the 'keypool' is regenerated and backed up.

"Security in depth" is always a good idea, so choosing a secure location for the backup and/or encrypting the backup before uploading it is recommended. And as in previous releases, if your machine is infected by malware there are several ways an attacker might steal your bitcoins.

Thanks to Alan Reiner (etotheipi) for finding and reporting this bug.

===0.4.0<ref>[https://bitcointalk.org/index.php?topic=45410.0 0.4 release announcement]</ref>===
Bitcoin version 0.4.0 is now available for download at:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.4.0/

The main feature in this release is wallet private key encryption;
you can set a passphrase that must be entered before sending coins.
See below for more information; if you decide to encrypt your wallet,
WRITE DOWN YOUR PASSPHRASE AND PUT IT IN A SECURE LOCATION. If you
forget or lose your wallet passphrase, you lose your bitcoins.
Previous versions of bitcoin are unable to read encrypted wallets,
and will crash on startup if the wallet is encrypted.

Also note: bitcoin version 0.4 uses a newer version of Berkeley DB
(bdb version 4.8) than previous versions (bdb 4.7). If you upgrade
to version 0.4 and then revert back to an earlier version of bitcoin
the it may be unable to start because bdb 4.7 cannot read bdb 4.8
"log" files.

Notable bug fixes from version 0.3.24:

Fix several bitcoin-becomes-unresponsive bugs due to multithreading
deadlocks.

Optimize database writes for large (lots of inputs) transactions
(fixes a potential denial-of-service attack)

Wallet Encryption

Bitcoin supports native wallet encryption so that people who steal your
wallet file don't automatically get access to all of your Bitcoins.
In order to enable this feature, choose "Encrypt Wallet" from the
Options menu. You will be prompted to enter a passphrase, which
will be used as the key to encrypt your wallet and will be needed
every time you wish to send Bitcoins. If you lose this passphrase,
you will lose access to spend all of the bitcoins in your wallet,
no one, not even the Bitcoin developers can recover your Bitcoins.
This means you are responsible for your own security, store your
passphrase in a secure location and do not forget it.

Remember that the encryption built into bitcoin only encrypts the
actual keys which are required to send your bitcoins, not the full
wallet. This means that someone who steals your wallet file will
be able to see all the addresses which belong to you, as well as the
relevant transactions, you are only protected from someone spending
your coins.

It is recommended that you backup your wallet file before you
encrypt your wallet. To do this, close the Bitcoin client and
copy the wallet.dat file from ~/.bitcoin/ on Linux, /Users/(user
name)/Application Support/Bitcoin/ on Mac OSX, and %APPDATA%/Bitcoin/
on Windows (that is /Users/(user name)/AppData/Roaming/Bitcoin on
Windows Vista and 7 and /Documents and Settings/(user name)/Application
Data/Bitcoin on Windows XP). Once you have copied that file to a
safe location, reopen the Bitcoin client and Encrypt your wallet.
If everything goes fine, delete the backup and enjoy your encrypted
wallet. Note that once you encrypt your wallet, you will never be
able to go back to a version of the Bitcoin client older than 0.4.

Keep in mind that you are always responsible for your own security.
All it takes is a slightly more advanced wallet-stealing trojan which
installs a keylogger to steal your wallet passphrase as you enter it
in addition to your wallet file and you have lost all your Bitcoins.
Wallet encryption cannot keep you safe if you do not practice
good security, such as running up-to-date antivirus software, only
entering your wallet passphrase in the Bitcoin client and using the
same passphrase only as your wallet passphrase.

See the doc/README file in the bitcoin source for technical details
of wallet encryption.

==0.3.X==

===0.3.24<ref>[https://bitcointalk.org/index.php?topic=27187.0 0.3.24 release announcement]</ref>===
Bitcoin v0.3.24 is now available for download at
https://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.24/

This is another bug fix release. We had hoped to have wallet encryption ready for release, but more urgent fixes for existing clients were needed -- most notably block download problems were getting severe. Wallet encryption is ready for testing at https://github.com/bitcoin/bitcoin/pull/352 for the git-savvy, and hopefully will follow shortly in the next release, v0.4.

Notable fixes in v0.3.24, and the main reasons for this release:

F1) Block downloads were failing or taking unreasonable amounts of time to complete, because the increased size of the block chain was bumping up against some earlier buffer-size DoS limits.

F2) Fix crash caused by loss/lack of network connection.

Notable changes in v0.3.24:

C1) DNS seeding enabled by default.

C2) UPNP enabled by default in the GUI client. The percentage of bitcoin clients that accept incoming connections is quite small, and that is a problem. This should help. bitcoind, and unofficial builds, are unchanged (though we encourage use of "-upnp" to help the network!)

C3) Initial unit testing framework. Bitcoin sorely needs automated tests, and this is a beginning. Contributions welcome.

C4) Internal wallet code cleanup. While invisible to an end user, this change provides the basis for v0.4's wallet encryption.

===0.3.23<ref>[https://bitcointalk.org/index.php?topic=16553.0 0.3.23 release announcement]</ref>===
Win32, Linux, MacOSX and source releases for bitcoin v0.3.23 have been uploaded to
https://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.23/

This is another quick bugfix release, trying to deal with the influx of new bitcoin users.

Main items of note:

* P2P connect-to-node logic changed to reduce timeout a bit. The network saw a huge influx of new users, who do not permit incoming connections. This change is a short-term hack, to more quickly hunt for useful P2P connections. Better "leaf node" logic is in the works, but this should let us limp along until then. One may use -upnp to properly forward ports, and help the network.
* Transaction fee reduced to 0.0005 for new transactions
* Client will relay transactions with fees as low as 0.0001 BTC

===0.3.22<ref>[https://bitcointalk.org/index.php?topic=12269.0 0.3.22 release announcement]</ref>===
Download URL: https://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.22/

This is largely a bugfix and TX fee schedule release. We also hope to make 0.3.23 a quick release, to fix problems that the network has seen due to explosive growth in the past week.

Notable changes:
* Client will accept and relay TX's with 0.0005 BTC fee schedule (users still pay 0.01 BTC per kb, until next version)
* Non-standard transactions accepted on testnet
* Source code tree reorganized (prep for autotools build)
* Remove "Generate Coins" option from GUI, and remove 4way SSE miner. Internal reference CPU miner remains available, but users are directed to external miners for best hash production.
* IRC is overflowing. Client now bootstraps to channels #bitcoin00 - #bitcoin99
* DNS names now may be used with -addnode, -connect (requires -dns to enable)

RPC changes:
* 'listtransactions' adds 'from' param, for range queries
* 'move' may take account balances negative
* 'settxfee' added, to manually set TX fee

===0.3.21<ref>[https://bitcointalk.org/index.php?topic=6642.0 0.3.21 release announcement]</ref>===
Binaries for Bitcoin version 0.3.21 are available at:
https://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.21/

Changes and new features from the 0.3.20 release include:

* Universal Plug and Play support. Enable automatic opening of a port for incoming connections by running bitcoin or bitcoind with the - -upnp=1 command line switch or using the Options dialog box.

* Support for full-precision bitcoin amounts. You can now send, and bitcoin will display, bitcoin amounts smaller than 0.01. However, sending fewer than 0.01 bitcoins still requires a 0.01 bitcoin fee (so you can send 1.0001 bitcoins without a fee, but you will be asked to pay a fee if you try to send 0.0001).

* A new method of finding bitcoin nodes to connect with, via DNS A records. Use the -dnsseed option to enable.

For developers, changes to bitcoin's remote-procedure-call API:

* New rpc command "sendmany" to send bitcoins to more than one address in a single transaction.

* Several bug fixes, including a serious intermittent bug that would sometimes cause bitcoind to stop accepting rpc requests.

* -logtimestamps option, to add a timestamp to each line in debug.log.

* Immature blocks (newly generated, under 120 confirmations) are now shown in listtransactions.

===0.3.20.2<ref>[https://bitcointalk.org/index.php?topic=4167.0 0.3.20.2 release announcement]</ref>===
The maxsendbuffer bug (0.3.20.1 clients not being able to download the block chain from other 0.3.20.1 clients) was only going to get
worse as people upgraded, so I cherry-picked the bug fix and created a minor release yesterday.

The Amazon Machine Images I used to do the builds are available:

ami-38a05251 Bitcoin-v0.3.20.2 Mingw (Windows; Administrator password 'bitcoin development')
ami-30a05259 Bitcoin_0.3.20.2 Linux32
ami-8abc4ee3 Bitcoin_0.3.20.2 Linux64

(mac build will be done soon)

If you have already downloaded version 0.3.20.1, please either add this to your bitcoin.conf file:

maxsendbuffer=10000
maxreceivebuffer=10000

... or download the new version.

===0.3.20.1===
(No known forum post.)

===0.3.20<ref>[https://bitcointalk.org/index.php?topic=2953.0 0.3.20 release announcement]</ref>===
Please checkout the git integration branch from:

https://github.com/bitcoin/bitcoin

... and help test. The new features that need testing are:

* -nolisten : https://github.com/bitcoin/bitcoin/pull/11
* -rescan : scan block chain for missing wallet transactions
* -printtoconsole : https://github.com/bitcoin/bitcoin/pull/37
* RPC gettransaction details : https://github.com/bitcoin/bitcoin/pull/24
* listtransactions new features : https://github.com/bitcoin/bitcoin/pull/10

Bug fixes that also need testing:

* -maxconnections= : https://github.com/bitcoin/bitcoin/pull/42
* RPC listaccounts minconf : https://github.com/bitcoin/bitcoin/pull/27
* RPC move, add time to output : https://github.com/bitcoin/bitcoin/pull/21
* ...and several improvements to --help output.

This needs more testing on Windows! Please drop me a quick private message, email, or IRC message if you are able to do some testing. If you find bugs, please open an issue at:

https://github.com/bitcoin/bitcoin/issues

===0.3.19<ref>[https://bitcointalk.org/index.php?topic=2228.0 0.3.19 release announcement]</ref>===
There's more work to do on DoS, but I'm doing a quick build of what I have so far in case it's needed, before venturing into more complex ideas. The build for this is version 0.3.19.

- Added some DoS controls
As Gavin and I have said clearly before, the software is not at all resistant to DoS attack. This is one improvement, but there are still more ways to attack than I can count.

I'm leaving the -limitfreerelay part as a switch for now and it's there if you need it.

- Removed "safe mode" alerts
"safe mode" alerts was a temporary measure after the 0.3.9 overflow bug. We can say all we want that users can just run with "-disablesafemode", but it's better just not to have it for the sake of appearances. It was never intended as a long term feature. Safe mode can still be triggered by seeing a longer (greater total PoW) invalid block chain.

===0.3.18<ref>[https://bitcointalk.org/index.php?topic=2162.0 0.3.18 release announcement]</ref>===

Changes:
* Fixed a wallet.dat compatibility problem if you downgraded from 0.3.17 and then upgraded again
* IsStandard() check to only include known transaction types in blocks
* Jgarzik's optimisation to speed up the initial block download a little

The main addition in this release is the Accounts-Based JSON-RPC commands that Gavin's been working on (more details at https://bitcointalk.org/index.php?topic=1886.0).
* getaccountaddress
* sendfrom
* move
* getbalance
* listtransactions

===0.3.17<ref>[https://bitcointalk.org/index.php?topic=1946.0 0.3.17 release announcement]</ref>===

Version 0.3.17 is now available.

Changes:
* new getwork, thanks m0mchil
* added transaction fee setting in UI options menu
* free transaction limits
* sendtoaddress returns transaction id instead of "sent"
* getaccountaddress <account>

The UI transaction fee setting was easy since it was still there from 0.1.5 and all I had to do was re-enable it.

The accounts-based commands: move, sendfrom and getbalance <account> will be in the next release. We still have some more changes to make first.

===0.3.16===

Never released.

===0.3.15<ref>[https://bitcointalk.org/index.php?topic=1780.0 0.3.15 release announcement]</ref>===

* paytxfee switch is now per KB, so it adds the correct fee for large transactions
* sending avoids using coins with less than 6 confirmations if it can
* BitcoinMiner processes transactions in priority order based on age of dependencies
* make sure generation doesn't start before block 74000 downloaded
* bugfixes by Dean Gores
* testnet, keypoololdest and paytxfee added to getinfo

===0.3.14<ref>[https://bitcointalk.org/index.php?topic=1528.0 0.3.14 release announcement]</ref>===

Version 0.3.14 is now available
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.14/

Changes:
* Key pool feature for safer wallet backup
Gavin Andresen:
* TEST network mode with switch -testnet
* Option to use SSL for JSON-RPC connections on unix/osx
* validateaddress RPC command
eurekafag:
* Russian translation

===0.3.13<ref>[https://bitcointalk.org/index.php?topic=1327.0 0.3.13 release announcement]</ref>===

Version 0.3.13 is now available. You should upgrade to prevent potential problems with 0/unconfirmed transactions. Note: 0.3.13 prevents problems if you haven't already spent a 0/unconfirmed transaction, but if that already happened, you need 0.3.13.2.

Changes:
* Don't count or spend payments until they have 1 confirmation.
* Internal version number from 312 to 31300.
* Only accept transactions sent by IP address if -allowreceivebyip is specified.
* Dropped DB_PRIVATE Berkeley DB flag.
* Fix problem sending the last cent with sub-cent fractional change.
* Auto-detect whether to use 128-bit 4-way SSE2 on Linux.
Gavin Andresen:
* Option -rpcallowip= to accept json-rpc connections from another machine.
* Clean shutdown on SIGTERM on Linux.

Download:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.13/

(Thanks Laszlo for the Mac OSX build!)

Note:
The SSE2 auto-detect in the Linux 64-bit version doesn't work with AMD in 64-bit mode. Please try this instead and let me know if it gets it right:
http://www.bitcoin.org/download/bitcoin-0.3.13.1-specialbuild-linux64.tar.gz

You can still control the SSE2 use manually with -4way and -4way=0.

Version 0.3.13.2 (SVN rev 161) has improvements for the case where you already had 0/unconfirmed transactions that you might have already spent. Here's a Windows build of it:
http://www.bitcoin.org/download/bitcoin-0.3.13.2-win32-setup.exe

===0.3.12<ref>[https://bitcointalk.org/index.php?topic=999.0 0.3.12 release announcement]</ref>===

Version 0.3.12 is now available.

Features:
* json-rpc errors return a more standard error object. (thanks to Gavin Andresen)
* json-rpc command line returns exit codes.
* json-rpc "backupwallet" command.
* Recovers and continues if an exception is caused by a message you received. Other nodes shouldn't be able to cause an exception, and it hasn't happened before, but if a way is found to cause an exception, this would keep it from being used to stop network nodes.

If you have json-rpc code that checks the contents of the error string, you need to change it to expect error objects of the form {"code":<number>,"message":<string>}, which is the standard. See this thread:
https://bitcointalk.org/index.php?topic=969.0

Download:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.3.12/

=References=
<references/>

BitcoinExchangeGuide

2019-12-03T09:47:27Z

Priem19: Typo.

[[File:BitcoinExchangeGuide.jpeg]]

===Overview===
Beginners Guide to the Various Bitcoin Exchanges

Contains third party neutral reviews of the most popular Bitcoin exchanges.

Website Helping New Adopters of Bitcoin Avoid Problem Exchanges such as Mt.Gox

Updated frequently with new information.

===History===

Founded in early 2014 after the fall of Mt.Gox.

The Site received over 2,000 uniques in the first 24 hours after release.

===External Links===
* [http://BitcoinExchangeGuide.com http://BitcoinExchangeGuide.com] Bitcoin Exchange Guide Website
* [http://bitcoinexchangeguide.com/bitcoin-introduction/ Bitcoin Exchange Guide - Introduction to BItcoin]

[[Category:Marketing]]
[[Category:Introduction]]

MPEx

2019-12-03T09:46:48Z

Priem19: /* History */ Typo.

An exchange where stocks, bonds, options and other types of securities are traded.

The exchange is offered and operated by Mircea Popescu of Romania. Facts and some history about this controversial person are collected on bitcointalk [https://bitcointalk.org/index.php?topic=102333.0 forum thread].
The site includes a very broad disclaimer of liability as well as the instruction (in red color) to "Read this whole thing first so you don't end up wasting bitcoins".

==Securities==
===Options===
The exchange offers options contracts under the American style where the buyer can execute the option at any time before the option expiry. Options may be executed at any time before the last Friday of the expiration month (up until midnight GMT of the Thursday evening that occurs before the last Friday of that option contract's month).

CALL and PUT options are priced in bitcoin and all funds for buying and selling options on this exchange occur in bitcoins. Additionally, the funds for executing options occurs only with bitcoins as well. For example, the quote for buying a call option will show a purchase price first computed in dollars but then the payment amount will be a conversion to BTCs based on the market exchange rate at the time of the quotation.

The option contract size is for one bitcoin (1.0 BTC). For example, buying a quantity of 100 CALL @5.0 contracts gives the buyer the option to purchase 100 BTC at $5.00 USD before the option expiry.

All positions are covered -- there are no "naked" short positions. For example, the seller of a 100 CALL @5.0 requires payment of 100 BTC plus the option premium to be sent to the exchange.

Quotations provided are either the best available from existing market positions offered (when size is shown under the "open" column) or are provided by the exchange's own market-making system and are good for order size of up to 1,000 contracts. Requests for quotation of larger sizes are available by contacting the exchange directly (via e-mail).

===Futures===
Commodity contracts settled in bitcoins are traded at MPEx.

At the launch of the futures exchange, the list of commodities futures includes: Eurodollar (CME), Nasdaq 100 (CME), Nikkei 225 (CME), S&P 500 (CME), WTI (NYMEX), Natural Gas (NYMEX), Heating Oil (NYMEX), Corn (CBOT), Soybeans (CBOT), Wheat (CBOT), Cocoa (ICE), Live Cattle (CME), Gold (COMEX), Silver (COMEX), Copper (COMEX), and Platinum (NYMEX).

===Stocks===
Traded at MPEx are shares of various equity issues, including shares of MPEx itself.

===Funds===
Various funds are offered for trade. Individual investment fund entities are managed by the fund's owner but are traded through MPEx.

===Bonds===
Bond issues are traded.

==Account Security==

Trading transactions and withdrawal requests require the message be signed using GPG.

==History==

The exchange first operated in 2011 as MPOe (Options Exchange). In February, 2012 the exchange began offering equity positions<ref>[http://polimedia.us/trilema/2012/sa-ne-jucam-de-a-investitiile-n-bitcoini/#comment-78745 Sa ne jucam de-a investitiile-n bitcoini. (English)]</ref>, <ref>[http://bitcointalk.org/index.php?topic=64962.0 Investing in Mircea Popescu's Options Emporium]</ref>. A third party operated a fund on [[GLBSE]] that held equity in the exchange as well<ref>[https://bitcointalk.org/index.php?topic=67535.0 MPOE ETF - Mircea Popescu's Option Emporium Exchange Traded Fund]</ref>.

On April 11, 2012 MPOe was rebranded as MPEx after the beta for MPEx had concluded<ref>[http://bitcointalk.org/index.php?topic=76239.0 MPEx goes live!]</ref>.

On December 10, 2012 the exchange began offering bitcoin-settled futures contracts<ref>[http://polimedia.us/trilema/2012/futures-on-mpex Futures on MPEx]</ref>.

==See Also==

* [http://wiki.bitcoin-otc.com/wiki/Option_orders Bitcoin-otc Option Orders]
* [http://polimedia.us/trilema/2012/glbse-vs-mpex-o-comparatie MPEx Comparison] versus competitor [[GLBSE]] (Romanian)
* [https://coinbr.com CoinBr - MPEx brokerage] that allows trading on MPEx without fee for creating new account

==External Links==

* [http://polimedia.us/bitcoin/mpex.php MPEx] website
* [http://bitcointalk.org/index.php?topic=67302.0 Using MPOE- A beginner's guide]
* [http://twitter.com/mpex1 @MPEx1] Twitter account
* {{Freenode IRC|bitcoin-assets}} Discussion of securities and other asset investments.

==External links==
* [http://mpex.biz/ Website]

==References==
<references />

[[Category:Exchanges]]
[[Category:Futures Exchanges]]
[[Category:Stock Exchanges]]

Alpaca

2019-12-03T09:44:49Z

Priem19: Fixes typo and broken links; changes some http to https.

One of the unofficial mascots for Bitcoin<ref>The others might include the Honey Badger.</ref>.

The connection between Bitcoin and the Alpaca likely originated from the February 10, 2011 post on Slashdot which described various goods and services could be purchased with bitcoins<ref>[https://slashdot.org/story/11/02/10/189246/Online-Only-Currency-BitCoin-Reaches-Dollar-Parity Online-Only Currency BitCoin Reaches Dollar Parity]</ref>. Because the slashdot crowd has a tendency to be critical (they summarized Apple's 2001 iPod announcement as "lame", for instance<ref>[https://slashdot.org/story/01/10/23/1816257/Apple-releases-iPod Apple releases iPod]</ref>) or humorous ("Do alpacas really wear socks?"<ref>[https://slashdot.org/comments.pl?sid=1989992&cid=35165074 Obvious question]</ref>) the meme involving the Alpaca was born.

The mention in Slashdot included a link to the page for a merchant, Grass Hill Alpacas, that sold Alpaca products for bitcoin<ref>[http://www.grasshillalpacas.com/alpacaproductsforbitcoinoffer.html Alpaca Products for Bitcoins]</ref>. He used that transaction in a subsequent article comparing using Bitcoin as a medium of exchange versus the coincidence of wants that a barter exchange suffers<ref>[https://www.cio.com.au/article/380394/open_source_identity_bitcoin_technical_lead_gavin_andresen Open source identity: Bitcoin technical lead Gavin Andresen]</ref>. Shortly after receiving the media mentions, most of the merchant's product offerings had sold out for the remainder of the season.

Bitcoin's former lead developer [[User:Gavinandresen|Gavin Andresen]] tweeted that he had purchased wool socks with bitcoins.

In March, 2011 the [[What is Bitcoin]]? video described Alpaca socks as one of the products Bitcoins could buy.

The reference to Alpaca socks has since been mentioned in quite a number of blog posts, news reports and videos occurring in the months since<ref>[http://www.forbes.com/forbes/2011/0509/technology-psilocybin-bitcoins-gavin-andresen-crypto-currency.html Crypto Currency]</ref>, <ref>[https://www.slate.com/id/2294980 My Money Is Cooler Than Yours]</ref>, <ref>[https://www.technologyreview.com/s/424091/what-bitcoin-is-and-why-it-matters/ What Bitcoin Is, and Why It Matters]</ref>, <ref>[https://www.npr.org/2011/05/24/136620231/what-are-bitcoins What Are Bitcoins?]</ref>, and <ref>[https://www.youtube.com/watch?v=gcn8cNCk9hM&t=471s The World's First Bitcoin Road Trip]</ref>.

The Bitcoin community has generally identified with the Alpaca and the Alpaca-Bitcoin meme. An example comes in a response on IRC following the conviction of Bernard Von NotHaus in which the U.S. DOJ labeled him a domestic terrorist for issuing a private currency<ref>[https://web.archive.org/web/20181116042550/https://www.silverbearcafe.com/private/03.11/thoughts.html Thoughts On The Liberty Dollar Debacle]</ref>. The quote "We are 'alpaca-sock-wearing crypto-terrorists'" resonated with Bitcoiners, and the meme persists<ref>[https://bitcointalk.org/index.php?topic=8416.msg123020#msg123020 We are "alpaca-sock-wearing crypto-terrorists"]</ref>.

==References==
<references />

[[Category:Introduction]]

Help:Introduction

2019-12-03T09:21:00Z

Priem19: /* Currency */ Broken URL replaced by wiki on the same topic which mentions the source of previous URL.

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 [https://en.bitcoin.it/wiki/Alpaca 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 [https://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, or their balance partially or wholly confiscated.
* Banks and other payment processors like PayPal, Visa, and Mastercard may refuse to process payments for certain 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 for a solution to a very difficult math problem the difficulty of which is precisely known. This difficulty is automatically adjusted on a predictable schedule so that the number of solutions found globally for a given unit of time is constant: the global system aims for 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]]". The solution itself is a [[Proof of work| proof-of-work]] or PoW. It is hard to find, but easy to verify.

Blocks create 12.5 new bitcoins at present [October 2016]. 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%. Originally the block reward was 50 bitcoins; it halved in November 2012; it then halved again in July 2016. 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 to Alice.
* Alice adds Bob’s address and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Alice signs the transaction with her private key, and announces her public key for signature verification.
* 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 address and the amount of bitcoins to transfer to a message: a 'transaction' message.
* Bob signs the transaction with his private key, and announces his public key for signature verification.
* 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 address with her address, 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:

:1PHYrmdJ22MKbJevpb3MBNpVckjZHt89hz

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 [https://btc.com/ BTC.com], [https://www.biteasy.com/ Biteasy.com], [https://blockchain.info/ Blockchain.info], [http://btc.blockr.io/ Blokr.io Bitcoin Block Explorer] or [https://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.

*In October 2014, according to [https://www.coindesk.com/state-of-bitcoin-q3-2014-report-maturing-ecosystem-price-pressure/ Coindesk report] there were more than 7.5 million bitcoin wallets.

*In October 2016, according to [https://Blockchain.info blockchain.info] user counts based on Blockchain wallet, there are about 8.8 mln registered Bitcoin users on its platform. [https://cointelegraph.com/news/counting-them-all-how-to-figure-out-actual-number-of-bitcoin-users Cointelegraph report]

*According to [https://blockchain.info/charts/my-wallet-n-users blockchain.info], from October 2016 till January 2018 the Bitcoin user base has almost tripled for total of 22 million users.

==See Also==
* [http://bitcoinhelp.net Bitcoin Help] — the simple guide to Bitcoin.
* Learn the entire history of Bitcoin in the interactive timeline at [http://historyofbitcoin.org History of Bitcoin].
* [https://www.weusecoins.com What Is Bitcoin?]
* [https://www.bitcoinmining.com What Is Bitcoin Mining?]

[[zh-cn:简介]]

[[de:Einführung]]
[[fr:Introduction]]