[preface] === Quick Glossary This quick glossary contains many of the terms used in relation to bitcoin. These terms are used throughout the book, so bookmark this for a quick reference. address:: A bitcoin address looks like +1DSrfJdB2AnWaFNgSbv3MZC2m74996JafV+. It consists of a string of letters and numbers starting with a "1" (number one). Just like you ask others to send an email to your email address, you would ask others to send you bitcoin to your bitcoin address.((("bitcoin address")))((("address", see="bitcoin address")))((("public key", see="bitcoin address"))) bip:: Bitcoin Improvement Proposals. A set of proposals that members of the bitcoin community have submitted to improve bitcoin. For example, BIP0021 is a proposal to improve the bitcoin uniform resource identifier (URI) scheme.((("bip"))) bitcoin:: The name of the currency unit (the coin), the network, and the software.((("bitcoin"))) block:: A grouping of transactions, marked with a timestamp, and a fingerprint of the previous block. The block header is hashed to produce a proof of work, thereby validating the transactions. Valid blocks are added to the main block chain by network consensus.((("block"))) block chain:: A list of validated blocks, each linking to its predecessor all the way to the genesis block.((("block chain"))) confirmations:: Once a transaction is included in a block, it has one confirmation. As soon as _another_ block is mined on the same block chain, the transaction has two confirmations, and so on. Six or more confirmations is considered sufficient proof that a transaction cannot be reversed.((("confirmations"))) difficulty:: A network-wide setting that controls how much computation is required to produce a proof of work.((("difficulty"))) difficulty target:: A difficulty at which all the computation in the network will find blocks approximately every 10 minutes.((("target difficulty"))) difficulty re-targeting:: A network-wide recalculation of the difficulty that occurs once every 2,106 blocks and considers the hashing power of the previous 2,106 blocks.((("difficulty re-targeting"))) fees:: The sender of a transaction often includes a fee to the network for processing the requested transaction. Most transactions require a minimum fee of 0.5mBTC.((("fees"))) hash:: A digital fingerprint of some binary input.((("hash"))) genesis block:: The first block in the blockchain, used to initialize the crypto-currency.((("genesis block"))) miner:: A network node that finds valid Proof-Of-Work for new blocks, by repeated hashing.((("miner"))) network:: A peer-to-peer network that propagates transactions and blocks to every bitcoin node on the network.((("network"))) Proof-Of-Work:: A piece of data that requires significant computation to find. In bitcoin, miners must find a numeric solution to the SHA256 algorithm that meets a network-wide target, the difficulty target. ((("proof-of-work"))) reward:: An amount included in each new block as a reward by the network to the miner who found the Proof-Of-Work solution. It is currently 25BTC per block.((("reward"))) secret key (aka private key):: The secret number that unlocks bitcoins sent to the corresponding address. A secret key looks like +5J76sF8L5jTtzE96r66Sf8cka9y44wdpJjMwCxR3tzLh3ibVPxh+.((("secret key")))((("private key", see="secret key"))) transaction:: In simple terms, a transfer of bitcoins from one address to another. More precisely, a transaction is a signed data structure expressing a transfer of value. Transactions are transmitted over the bitcoin network, collected by miners, and included into blocks, made permanent on the blockchain.((("transaction"))) wallet:: Software that holds all your bitcoin addresses and secret keys. Use it to send, receive, and store your bitcoin.((("wallet")))