reverting recent removals, see Talk:Bitcoin#Removals at "mods direction"
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Revision as of 09:20, 2 January 2017
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A variation in difficulty is achieved by requiring that this integer is below a certain threshold - the data in the block is perturbed by a [[Wikipedia:Cryptographic nonce|nonce value]], until the data in the block hashes to produce an integer below the threshold - which takes a lot of processing power. The threshold is set by the number of people currently mining for bitcoins so as to achieve a general speed of about 1 block every 10 minutes.
A variation in difficulty is achieved by requiring that this integer is below a certain threshold - the data in the block is perturbed by a [[Wikipedia:Cryptographic nonce|nonce value]], until the data in the block hashes to produce an integer below the threshold - which takes a lot of processing power. The threshold is set by the number of people currently mining for bitcoins so as to achieve a general speed of about 1 block every 10 minutes.
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== Consensus ==
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The consensus rules are the specific set of rules that all Bitcoin full nodes will unfailingly enforce when considering the validity of a block and its transactions. For example, the Bitcoin consensus rules require that blocks only create a certain number of bitcoins. If a block creates more bitcoins than is allowed, all full nodes will reject this block, even if every other node and miner in the world accepts it. Adding new consensus rules can generally be done as a softfork, while removing any consensus rule requires a hardfork. Rules regarding the behavior of the mere network protocol are not consensus rules, even if a change to the network protocol behavior breaks backward-compatibility. The consensus rules are only concerned with the validity of blocks and transactions.
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These rules are called consensus rules because Bitcoin requires that all participants in the Bitcoin economy have consensus (with the meaning of the next definition) as to the consensus rules. If the economy disagrees about the consensus rules, then the currency and economy splits into two or more totally-independent pieces.
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{{Warning|It is ''integral'' to understand that you are only capable of transacting with parties with which you are in consensus, should your personal consensus with the network be broken, or consensus of the network at large be broken, you will only be able to transact with those parties with which you are in consensus.}}
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Citation: https://en.bitcoin.it/wiki/Consensus
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=== Nature of Consensus Failure ===
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The nature of consensus is a very strict yet completely voluntary uncoordinated interaction of many independent users. It is both a requirement of the networks correct operation, and a facilitator of its correct operation at the same time. You can be considered to be in consensus with any other node that will accept any data structure relevant to consensus as valid that you have accepted as valid (ignoring of course an instance where two different miners both find valid blocks at the same time and each relay theirs to part of the network, the next valid block will decide which preceding block was valid based on which one it extends from). Consensus can be broken violating explicit consensus rules (violating a rule explicitly spelled out as a consensus rule, i.e. the cap of 21 million bitcoin, rate at which they are issued, the maximum size of a block, that a transaction is only valid if citing a valid unspent coin, etc.) or violating unexplicit rules (due to a bug or unintended consequence of design, i.e. a valid structure erroneously being invalidated due to software bug/improper format/etc., or the use of an attack avenue to overstress the node with load due to a bug or bad design). Both types of consensus failures could potentially come to be intentionally or unintentionally.
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A discussion of two consensus breaks in Bitcoin Core's history, one explicit, one unexplicit: https://bitcointalk.org/index.php?topic=702755.0
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A discussion of design flaw on reddit (with citation links to official developers discussion): https://www.reddit.com/r/Bitcoin/comments/5h70s3/bitcoin_unlimited_bu_the_developers_have_realized/
== Installation ==
== Installation ==
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== Bitcoin Software ==
== Bitcoin Software ==
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{{Warning|In order to transact or interact with other clients you must be running compatible software. This is currently a complicated and contentious matter in the Bitcoin community, it is advised you '''thoroughly''' research your clients compatibility with others. See [https://en.bitcoin.it/wiki/Consensus Consensus]}}
=== Full Nodes ===
=== Full Nodes ===
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{{Style|Whether a client is "consensus-compatible" or not seems to be the main purpose of this section, yet the term is not defined and none of the claims surrounding it are referenced}}
{{Style|Whether a client is "consensus-compatible" or not seems to be the main purpose of this section, yet the term is not defined and none of the claims surrounding it are referenced}}
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{{Warning|There are many different proposals to alter the consensus rules of the Bitcoin network, with different applications implementing different alterations. This section attempts to provide an overview of the software in the Bitcoin ecosystem, both those that attempt to implement alterations to consensus rules and those that do not. Applications listed here have the intention of interacting with the main network of Bitcoin nodes, and only implement protocol changes when their specific clients mechanism for doing so reaches its activation threshold (which differs depending on the client). It is advised to research thoroughly before use, in order to find the best fit for your use case. Be warned that choosing a consensus-incompatible node may result in you being forked off the bitcoin blockchain and result in you using some other currency that is not bitcoin. Also be warned that operating a minority implementation sharing consensus rules with another implementation also carries a risk of bugs or design flaws causing a fork or consensus failure. See [[#Consensus]].}}
==== Bitcoin Core ====
==== Bitcoin Core ====
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[https://bitcoincore.org/ Official Website]
[https://bitcoincore.org/ Official Website]
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=== Re-implementations ===
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{{Note|The following clients have re-implemented the consensus rules enforced by Bitcoin Core either from scratch with a new codebase, or by forking from Core's codebase, with the intent of continuing to follow the consensus rules enforced by Bitcoin Core.}}
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==== Bitcoin Knots ====
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Consensus-compatible software fork of Bitcoin Core. Mostly maintained by Core Developer Luke-jr, for features that don't make it into the main project.
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[https://bitcoinknots.org/ Official Website]
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[https://bitcoinknots.org/#features Features list]
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==== BTCD ====
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Consensus-compatible node and software library written in Golang.
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[https://github.com/btcsuite/btcd Official Website]
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==== BCoin ====
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Consensus-compatible node and software library written in JavaScript.
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[https://github.com/bcoin-org/bcoin Official Website]
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==== Toshi ====
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Consensus-compatible node and software library written in Ruby and released by the [https://coinbase.com Coinbase] company.
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[https://github.com/coinbase/toshi Website]
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{{Note|This client is no longer used by Coinbase, who runs Bitcoin Core, because of multiple bugs causing them to fork off the network in multiple instances.}}
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=== Diverging Implementations ===
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{{Note|The following clients have been forked away from Core's codebase, with many different modifications made to consensus related and non consensus related code, with the intent to upon the activation conditions laid out by each client initiate a break in consensus to continue a new diverging fork under different consensus rules than currently enforced by the majority of the network.}}
==== Bitcoin Classic ====
==== Bitcoin Classic ====
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[https://bitcoinclassic.com/ Bitcoin Classic] has a statement on blocksize [https://bitcoinclassic.com/devel/Blocksize.html here].
[https://bitcoinclassic.com/ Bitcoin Classic] has a statement on blocksize [https://bitcoinclassic.com/devel/Blocksize.html here].
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This client is potentially consensus-incompatible with the rest of the network, and upon conditions being met will fork away from the previous chain and consensus rules.
{{Note|In Bitcoin Classic the block size is no longer limited by rules set by software developers. It is set by you, the person running the software. This runs the very real risk of adding support to raising the blocksize to a point your hardware cannot provide the necessary resources to fully validate the blockchain.}}
{{Note|In Bitcoin Classic the block size is no longer limited by rules set by software developers. It is set by you, the person running the software. This runs the very real risk of adding support to raising the blocksize to a point your hardware cannot provide the necessary resources to fully validate the blockchain.}}
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Bitcoin Unlimited can be found in {{AUR|bitcoind-unlimited-git}}
Bitcoin Unlimited can be found in {{AUR|bitcoind-unlimited-git}}
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Consensus-incompatible implementation that [https://www.bitcoinunlimited.info/faq Removes the block size limit completely].
{{Note|In Bitcoin Unlimited the block size is no longer limited by rules set by software developers. It is set by you, the person running the software. This runs the very real risk of adding support to raising the blocksize to a point your hardware cannot provide the necessary resources to fully validate the blockchain.}}
{{Note|In Bitcoin Unlimited the block size is no longer limited by rules set by software developers. It is set by you, the person running the software. This runs the very real risk of adding support to raising the blocksize to a point your hardware cannot provide the necessary resources to fully validate the blockchain.}}
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Bitcoin XT can be found in {{AUR|bitcoinxt-gui-git}}
Bitcoin XT can be found in {{AUR|bitcoinxt-gui-git}}
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Implementation similar to Bitcoin Classic which also implements [https://bitcoinxt.software/patches.html multiple patches] aimed at improving the network's throughput.
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Implementation similar to Bitcoin Classic which also implements [https://bitcoinxt.software/patches.html multiple patches] aimed at improving the network's throughput.
This
client is
potentially consensus-incompatible with the rest of the network, and upon conditions being met will fork away from the previous chain and consensus rules
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{{Note|Upon reaching activation threshold this
client is
designed to modify its acceptable blocksize
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[https://bitcoinxt.software/ Official Website]
[https://bitcoinxt.software/ Official Website]
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Thin clients do not fully validate the blockchain or compute a full UTXO set. They derive their security in proxy by connecting to a fullnode and downloading the blockheaders. They are still able to guarantee the Proof of Work behind a block is valid, and each blockheader contains a merkle root of all the transactions in the block. This allows them to query full node clients for the blockheaders and the data to prove their transaction is in the merkle root in the blockheader. They however must trust that miners are mining valid blocks, and have no way to make sure rules like the issuance rate or cap of Bitcoins are being followed.
Thin clients do not fully validate the blockchain or compute a full UTXO set. They derive their security in proxy by connecting to a fullnode and downloading the blockheaders. They are still able to guarantee the Proof of Work behind a block is valid, and each blockheader contains a merkle root of all the transactions in the block. This allows them to query full node clients for the blockheaders and the data to prove their transaction is in the merkle root in the blockheader. They however must trust that miners are mining valid blocks, and have no way to make sure rules like the issuance rate or cap of Bitcoins are being followed.
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{{Warning|In the event of a consensus failure at large on the network, or one affecting the node(s) an SPV client is connected to, the SPV client is incapable of detecting which partition of the network it is on, or communicating to, or being sent information by. It is extremely insecure to send or receive money with an SPV client in the event of such a consensus failure occurring.}}
==== Electrum ====
==== Electrum ====