Prevailing bitcoin logo

Prevailing bitcoin logo
Ticker symbolBTC, XBT[b]
CoinsUnspent outputs of transactions (in multiples of a satoshi)[3]:ch. 5
Original author(s)Satoshi Nakamoto
White paper“Bitcoin: A Peer-to-Peer Electronic Cash System”[4]
Implementation(s)Bitcoin Core
Initial release0.1.0 / 9 January 2009 (9 years ago)
Latest release0.16.1 / 15 June 2018 (41 days ago)
Ledger start3 January 2009 (9 years ago)
Timestamping schemeProof-of-work (partial hash inversion)
Hash functionSHA-256
IssuanceDecentralized (block reward)[6][7]
Block reward₿12.5[c]
Block time10 minutes
Circulating supply₿16,858,762 (as of 11 February 2018)
Supply limit₿21,000,000 [5]
  1. Jump up^ The symbol was encoded in Unicode version 10.0 at position U+20BF ₿ BITCOIN SIGN in the Currency Symbols block in June 2017.[1]
  2. Jump up^ Compatible with ISO 4217.
  3. Jump up^ July 2016 to approximately June 2020, halved approximately every four years

Bitcoin () is a cryptocurrency, a form of electronic cash. It was designed to work as a decentralized digital currency without a central bank or single administrator, though in practice many aspects of its use are centralized.[8]:215, 219–222[9]:3

Bitcoins can be sent from user to user on the peer-to-peer bitcoin network directly, without the need for intermediaries, though intermediaries are widely used.[8]:220–222 Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented by an unknown person or group of people using the name Satoshi Nakamoto[10] and released as open-source software in 2009.[11] Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,[12] products, and services. Research produced by the University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.[13]

Bitcoin has been criticized for its use in illegal transactions, its high electricity consumption, price volatility, thefts from exchanges, and the possibility that bitcoin is an economic bubble.[14] Several regulatory agencies have issued investor alerts about bitcoin.[15]