Bitcoin[note 5][note 6] is a digital asset[17] and a payment system invented by Satoshi Nakamoto, who published the invention in 2008[13] and released it as open-source software in 2009.[18] The system is peer-to-peer and transactions take place between users directly, without an intermediary.[19]:4 These transactions are verified by network nodes and recorded in a public distributed ledger called the block chain,[20] which uses bitcoin as its unit of account. Since the system works without a central repository or single administrator, the U.S. Treasury categorizes bitcoin as a decentralized virtual currency.[1] Bitcoin is often called the first cryptocurrency,[21][22][23] although prior systems existed[note 7] and it is more correctly described as the first decentralized digital currency.[19][26] Bitcoin is the largest of its kind in terms of total market value.[27]
Bitcoins are created as a reward for payment processing work in which users offer their computing power to verify and record payments into the public ledger. This activity is called mining and miners are rewarded with transaction fees and newly created bitcoins.[19] Besides being obtained by mining, bitcoins can be exchanged for other currencies,[28] products, and services.[29] When sending bitcoins, users can pay an optional transaction fee to the miners.[30]
In February 2015, the number of merchants accepting bitcoin for products and services passed 100,000.[31] Proponents of the currency argue that merchants have an incentive to accept bitcoin because its fees are lower than the 2–3% typically imposed by credit card processors.[32] Despite the fourfold increase in the number of merchants accepting bitcoin in 2014, the cryptocurrency did not have much momentum in retail transactions.[33] The European Banking Authority[34] and other sources[19]:11 have warned that bitcoin users are not protected by refund rights or chargebacks. The use of bitcoin by criminals has attracted the attention of financial regulators,[35] legislative bodies,[36] law enforcement,[37] and media.[38] Criminal activities are primarily centered around black markets and theft, though officials in countries such as the United States also recognize that bitcoin can provide legitimate financial services.[39]
The identity of the pseudononymous 'Satoshi Nakamoto' has been the subject of speculation. Craig Steven Wright claims that he is Mr. Nakamoto.[40][41]
