The bitcoin network is a 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.