Bitcoin

Bitcoin (₿)

 is a cryptocurrency, a form of electronic cash. It is a decentralized digital currency without a central bank or single administrator that can be sent from user to user on the peer-to-peer bitcoin network without the need for intermediaries.^[7]

Bitcoin
Prevailing bitcoin logo
Denominations
Plural	bitcoins
Symbol	₿[a]
Ticker symbol	BTC, XBT[b]
Subunits
​1⁄1000	millibitcoin
​1⁄100000000	satoshi[2]
Coins	Unspent outputs of transactions (in multiples of a satoshi)[3]:ch. 5
Development
Original author(s)	Satoshi Nakamoto
White paper	"Bitcoin: A Peer-to-Peer Electronic Cash System"[5]
Implementation(s)	Bitcoin Core
Initial release	0.1.0 / 9 January 2009(10 years ago)
Latest release	0.17.1 / 25 December 2018 (2 months ago)[4]
Website	bitcoin.org
Ledger
Ledger start	3 January 2009 (10 years ago)
Timestamping scheme	Proof-of-work (partial hash inversion)
Hash function	SHA-256
Issuance	Decentralized (block reward)[7][8]
Block reward	₿12.5[c]
Block time	10 minutes
Block explorer	bitaps.com
Circulating supply	₿17,560,833 (as of 27 February 2019)
Supply limit	₿21,000,000[6]
^ The symbol was encoded in Unicode version 10.0 at position U+20BF ₿ BITCOIN SIGN in the Currency Symbols block in June 2017.[1] ^ Compatible with ISO 4217. ^ July 2016 to approximately June 2020, halved approximately every four years

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Transactions are verified by network nodesthrough 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^[9] and released as open-source software in 2009.^[10] Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,^[11]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.^[12]

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.^[13] Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.^[14]