Bitcoin[a] (₿) is a cryptocurrency invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto. The currency began use in 2009 when its implementation was released as open-source software.:ch. 1
Bitcoin 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. Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. Research produced by the University of Cambridge estimated that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.
Bitcoin has been criticized for its use in illegal transactions, the large amount of electricity used by miners, price volatility, and thefts from exchanges. Some economists, including several Nobel laureates, have characterized it as a speculative bubble at various times. Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.
On 15 July 2017, the controversial Segregated Witness [SegWit] software upgrade was approved (“locked-in”). Segwit was intended to support the Lightning Network as well as improve scalability. SegWit was subsequently activated on the network on 24 August 2017. The bitcoin price rose almost 50% in the week following SegWit’s approval. On 21 July 2017, bitcoin was trading at $2,748, up 52% from 14 July 2017’s $1,835. Supporters of large blocks who were dissatisfied with the activation of SegWit forked the software on 1 August 2017 to create Bitcoin Cash.
In September 2018, an anonymous party discovered and reported an invalid-block denial-of-server vulnerability to developers of Bitcoin Core, Bitcoin ABC and Bitcoin Unlimited. Further analysis by bitcoin developers showed the issue could also allow the creation of blocks violating the 21 million coin limit and CVE-2018-17144 was assigned and the issue resolved.[non-primary source needed]
Bitcoin prices were negatively affected by several hacks or thefts from cryptocurrency exchanges, including thefts from Coincheck in January 2018, Bithumb in June, and Bancor in July. For the first six months of 2018, $761 million worth of cryptocurrencies was reported stolen from exchanges
According to CoinMetrics and Forbes, on 11 March 281,000 bitcoins were sold by owners who held them for only thirty days. This compared to ₿4,131 that had laid dormant for a year or more, indicating that the vast majority of the bitcoin volatility on that day was from recent buyers. During the week of 11 March 2020 as a result of the COVID-19 pandemic, cryptocurrency exchange Kraken experienced an 83% increase in the number of account signups over the week of bitcoin’s price collapse, a result of buyers looking to capitalize on the low price. On 13 March 2020, bitcoin fell below $4000 during a broad COVID-19 pandemic related market selloff, after trading above $10,000 in February 2020.
In August 2020, MicroStrategy invested $250 million in bitcoin as a treasury reserve asset. In October 2020, Square, Inc. put approximately 1% of their total assets ($50 million) in bitcoin. In November 2020, PayPal announced that all users in the US could buy, hold, or sell bitcoin using PayPal. On 30 November 2020, bitcoin hit a new all-time high of $19,860 topping the previous high from December 2017. Alexander Vinnik, founder of BTC-e, was convicted and sentenced to 5 years in prison for money laundering in France while refusing to testify during his trial. In December 2020 Massachusetts Mutual Life Insurance Company announced it has purchased $100 million in bitcoin, or roughly 0.04% of its general investment account.
On 19 January 2021 Elon Musk placed #Bitcoin in his Twitter profile tweeting “In retrospect, it was inevitable”, which caused the price to briefly rise about $5000 in an hour to $37,299. On 25 January 2021 Microstrategy announced it continued to buy bitcoin and as of the same date it had holdings of ₿70,784 worth $2.38 billion. On 8 February 2021 Tesla’s announcement that it had purchased $1.5 billion in bitcoin and planned to start accepting bitcoin as payment for vehicles pushed the bitcoin price to an all time high of $44,141. On 18 February 2021, Elon Musk said that “owning bitcoin was only a little better than holding conventional cash, but that the slight difference made it a better asset to hold”.
It was announced in September 2020, that the Canton of Zug (in Switzerland) will start to accept tax payments in bitcoin from February 2021.