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(詳細はpeer-to-peer payment network that operates on a cryptographic protocol. Users send bitcoins, the units of currency, by broadcasting digitally signed messages to the network using bitcoin wallet software. Transactions are recorded into a distributed public database known as the block chain, with consensus achieved by a proof-of-work system called "mining". The block chain is distributed internationally using peer-to-peer filesharing technology similar to BitTorrent. The protocol was designed in 2008 and released in 2009 as open source software by "Satoshi Nakamoto", the pseudonym of the original developer or group of developers. The network timestamps transactions by including them in blocks that form an ongoing chain called the block chain. Such blocks cannot be changed without redoing the work that was required to create each block since the modified block. The longest chain serves not only as proof of the sequence of events but also records that this sequence of events was verified by a majority of the bitcoin network's computing power. As long as a majority of computing power is controlled by nodes that are not cooperating to attack the network, they will generate the longest chain of records and outpace attackers. The network itself requires minimal structure to share transactions. Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will. Upon reconnection, a node will download and verify new blocks from other nodes to complete its local copy of the block chain. ==Transactions== A transaction is a section of data confirmed by a signature. It is sent to the bitcoin network and forms blocks. It typically contains references to preceding transactions and associates a certain number of bitcoins with one or several public keys (bitcoin addresses). It is not encrypted because there is nothing to encrypt in the bitcoin system. A block chain browser is where all transactions are combined in the form of a block chain. They can be found and verified. This is necessary to determine technical transaction parameters as well as verify the details of payments.〔(Bitcoin Wiki - Transaction )〕 A bitcoin is defined by a sequence of digitally signed transactions that began with its creation as a block reward. The owner of a bitcoin transfers it to the next owner by digitally signing it over to the next owner in a bitcoin transaction, much like endorsing a traditional bank check. A payee can verify each previous transaction to verify the chain of ownership. Unlike traditional check endorsement, bitcoin transactions are irreversible, which eliminates risk of chargeback fraud. A bitcoin is a currency object — an entity which is traded, though nothing prevents trades in fractions of, or multiple bitcoins. Bitcoins are intended to be fungible, though each has its own distinct history. Although it would be possible to handle bitcoins individually, it would be unwieldy to make a separate transaction for every satoshi in a transfer. Transactions are therefore allowed to contain multiple inputs and outputs, and in that way bitcoins can be split and combined. Common transactions will have either a single input from a larger previous transaction or multiple inputs combining smaller amounts, and one or two outputs: one for the payment, and one returning the change, if any, back to the sender. Any difference between the total input and output amounts of a transaction is offered to miners as a transaction fee.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bitcoin network」の詳細全文を読む スポンサード リンク
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