As specified by the Bitcoin protocol, each miner is rewarded by each block mined.  Currently, that reward is 12.5 new Bitcoins for each block mined. The Bitcoin block mining reward halves every 210,000 blocks, when the coin reward will decrease from 12.5 to 6.25 coins.  Currently, the total number of Bitcoins left to be mined amounts to 4,293,388. This means that 16,706,613 Bitcoins are in circulation, and that the total number of blocks available until mining reward is halved is 133,471 blocks till 11:58:04 12th Jun, 2020 When the mining reward will be halved.
In March 2013 the blockchain temporarily split into two independent chains with different rules. The two blockchains operated simultaneously for six hours, each with its own version of the transaction history. Normal operation was restored when the majority of the network downgraded to version 0.7 of the bitcoin software.[36] The Mt. Gox exchange briefly halted bitcoin deposits and the price dropped by 23% to $37[37][38] before recovering to previous level of approximately $48 in the following hours.[39] The US Financial Crimes Enforcement Network (FinCEN) established regulatory guidelines for "decentralized virtual currencies" such as bitcoin, classifying American bitcoin miners who sell their generated bitcoins as Money Service Businesses (MSBs), that are subject to registration or other legal obligations.[40][41][42] In April, exchanges BitInstant and Mt. Gox experienced processing delays due to insufficient capacity[43] resulting in the bitcoin price dropping from $266 to $76 before returning to $160 within six hours.[44] The bitcoin price rose to $259 on 10 April, but then crashed by 83% to $45 over the next three days.[34] On 15 May 2013, US authorities seized accounts associated with Mt. Gox after discovering it had not registered as a money transmitter with FinCEN in the US.[45][46] On 23 June 2013, the US Drug Enforcement Administration (DEA) listed 11.02 bitcoins as a seized asset in a United States Department of Justice seizure notice pursuant to 21 U.S.C. § 881.[47] This marked the first time a government agency had seized bitcoin.[48][49] The FBI seized about 26,000 bitcoins in October 2013 from the dark web website Silk Road during the arrest of Ross William Ulbricht.[50][51][52] Bitcoin's price rose to $755 on 19 November and crashed by 50% to $378 the same day. On 30 November 2013 the price reached $1,163 before starting a long-term crash, declining by 87% to $152 in January 2015.[34] On 5 December 2013, the People's Bank of China prohibited Chinese financial institutions from using bitcoins.[53] After the announcement, the value of bitcoins dropped,[54] and Baidu no longer accepted bitcoins for certain services.[55] Buying real-world goods with any virtual currency had been illegal in China since at least 2009.[56]
The bitcoin blockchain is a public ledger that records bitcoin transactions.[64] It is implemented as a chain of blocks, each block containing a hash of the previous block up to the genesis block[a] of the chain. A network of communicating nodes running bitcoin software maintains the blockchain.[30]:215–219 Transactions of the form payer X sends Y bitcoins to payee Z are broadcast to this network using readily available software applications.
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[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]
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