Published on Feb 21, 2020
Bitcoin is a cryptocurrency and worldwide payment system. It is the first decentralized digital currency. Its conception is peer-to-peer and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes through the use of cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented by an unknown person or group of people under the name Satoshi Nakamoto and released as open-source software in 2009.
Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment. Research produced by the University of Cambridge estimates that in 2017, there are 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.
Mining is a record-keeping service done through the use of computer processing power. Miners keep the blockchain consistent, complete, and unalterable by repeatedly grouping newly broadcast transactions into a block, which is then broadcast to the network and verified by recipient nodes. Each block contains a SHA-256 cryptographic hash of the previous block, thus linking it to the previous block and giving the blockchain its name.
To be accepted by the rest of the network, a new block must contain a so-called proof-of-work.The system used is based on Adam Back's 1997 anti-spam scheme, Hashcash. The PoW requires miners to find a number called a nonce, such that when the block content is hashed along with the nonce, the result is numerically smaller than the network's difficulty target. This proof is easy for any node in the network to verify, but extremely time-consuming to generate, as for a secure cryptographic hash, miners must try many different nonce values (usually the sequence of tested values is the ascending natural numbers: 0, 1, 2, 3, ...[5]:ch. 8) before meeting the difficulty target.
Every 2,016 blocks (approximately 14 days at roughly 10 min per block), the difficulty target is adjusted based on the network's recent performance, with the aim of keeping the average time between new blocks at ten minutes. In this way the system automatically adapts to the total amount of mining power on the network.[5]:ch. 8 Between 1 March 2014 and 1 March 2015, the average number of nonces miners had to try before creating a new block increased from 16.4 quintillion to 200.5 quintillion.
The proof-of-work system, alongside the chaining of blocks, makes modifications of the blockchain extremely hard, as an attacker must modify all subsequent blocks in order for the modifications of one block to be accepted.[60] As new blocks are mined all the time, the difficulty of modifying a block increases as time passes and the number of subsequent blocks (also called confirmations of the given block) increases.
Bitcoin price[g] history chart, linear scale. Year numbers are placed around the middle of the designated year.
The price of bitcoins has gone through various cycles of appreciation and depreciation referred to by some as bubbles and busts.[142][143] In 2011, the value of one bitcoin rapidly rose from about US$0.30 to US$32 before returning to US$2.[144] In the latter half of 2012 and during the 2012–13 Cypriot financial crisis, the bitcoin price began to rise, reaching a high of US$266 on 10 April 2013, before crashing to around US$50. On 29 November 2013, the cost of one bitcoin rose to a peak of US$1,242. In 2014, the price fell sharply, and as of April remained depressed at little more than half 2013 prices. As of August 2014 it was under US$600.
According to Mark T. Williams, as of 2014, bitcoin has volatility seven times greater than gold, eight times greater than the S&P 500, and 18 times greater than the US dollar.[149] According to Forbes, there are uses where volatility does not matter, such as online gambling, tipping, and international remittances.
In January 2015, noting that the bitcoin price had dropped to its lowest level since spring 2013 – around US$224 – The New York Times suggested that "[w]ith no signs of a rally in the offing, the industry is bracing for the effects of a prolonged decline in prices. In particular, bitcoin mining companies, which are essential to the currency's underlying technology, are flashing warning signs." Also in January 2015, Business Insider reported that deep web drug dealers were "freaking out" as they lost profits through being unable to convert bitcoin revenue to cash quickly enough as the price declined – and that there was a danger that dealers selling reserves to stay in business might force the bitcoin price down further.
According to an article in The Wall Street Journal, as of 19 April 2016, bitcoin had been more stable than gold for the preceding 24 days, and it was suggested that its value might be more stable in the future. On 3 March 2017, the price of a bitcoin surpassed the market value of an ounce of gold for the first time as its price surged to an all-time high of $1,268. A study in Electronic Commerce Research and Applications, going back through the network's historical data, showed the value of the bitcoin network as measured by the price of bitcoins, to be roughly proportional to the square of the number of daily unique users participating on the network, i.e. that the network is "fairly well modeled by the Metcalfe's law
The blockchain is a public ledger that records bitcoin transactions. A novel solution accomplishes this without any trusted central authority: the maintenance of the blockchain is performed by a network of communicating nodes running bitcoin software. Transactions of the form payer X sends Y bitcoins to payee Z are broadcast to this network using readily available software applications.[ Network nodes can validate transactions, add them to their copy of the ledger, and then broadcast these ledger additions to other nodes. The blockchain is a distributed database – to achieve independent verification of the chain of ownership of any and every bitcoin amount, each network node stores its own copy of the blockchain. Approximately six times per hour, a new group of accepted transactions, a block, is created, added to the blockchain, and quickly published to all nodes. This allows bitcoin software to determine when a particular bitcoin amount has been spent, which is necessary in order to prevent double-spending in an environment without central oversight. Whereas a conventional ledger records the transfers of actual bills or promissory notes that exist apart from it, the blockchain is the only place that bitcoins can be said to exist in the form of unspent outputs of transactions
Bitcoin has been labelled a speculative bubble by many including former Fed Chairman Alan Greenspan and economist John Quiggin. Nobel Memorial Prize laureate Robert Shiller said that bitcoin "exhibited many of the characteristics of a speculative bubble". Journalist Matthew Boesler in 2013 rejected the speculative bubble label and saw bitcoin's quick rise in price as nothing more than normal economic forces at work. Timothy B. Lee, in a 2013 piece for The Washington Post pointed out that the observed cycles of appreciation and depreciation don't correspond to the definition of speculative bubble. On 14 March 2014, the American business magnate Warren Buffett said, "Stay away from it. It's a mirage, basically." During their time as bitcoin developers, Gavin Andresen and Mike Hearn warned that bubbles may occur
