Bitcoin is a decentralized digital currency created by an unknown person or group of people under the name Satoshi Nakamoto and released as open-source software in 2009. It does not rely on a central server to process transactions or store funds. There are a maximum of 2,099,999,997,690,000 Bitcoin elements (called Satoshis, the unit has been named in collective homage to the original creator), which are currently most commonly measured in units of 100,000,000 known as BTC. There will only ever be 21 million Bitcoin (BTC) to ever be created.
As of January 2018, it is the most widely used alternative currency,now with the total market cap around 250 billion US dollars.
Bitcoin has no central issuer; instead, the peer-to-peer network regulates Bitcoins, transactions and issuance according to consensus in network software. These transactions are verified by network nodes through the use of cryptography and recorded in a public distributed ledger called a blockchain.
Bitcoins are issued to various nodes that verify transactions through computing power; it is established that there will be a limited and scheduled release of no more than 21 million BTC worth of coins, which will be fully issued by the year 2140.
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 were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using Bitcoin.
Internationally, Bitcoins can be exchanged and managed through various websites and software along with physical banknotes and coins.
In 2008, Satoshi Nakamoto published a paperon The Cryptography Mailing list at describing the Bitcoin protocol.
The Bitcoin network came into existence on 3 January 2009 with the release of the first Bitcoin client, wxBitcoin, and the issuance of the first Bitcoins. The most significant transaction involved a 10,000 BTC pizza.
In 2011, Wikileaks,Freenet,Singularity Institute,Internet Archive,Free Software Foundation and others, began to accept donations in Bitcoin. The Electronic Frontier Foundation did so for a while but has since stopped, citing concerns about a lack of legal precedent about new currency systems, and because they "generally don't endorse any type of product or service."Some small businesses had started to adopt Bitcoin.
Bitcoin is administered through a decentralized peer-to-peer network. Cryptographic technologies and the peer-to-peer network of computing power enables users to make and verify irreversible, instant online Bitcoin payments, without an obligation to trust and use centralized banking institutions and authorities. Dispute resolution services are not made directly available. Instead it is left to the users to verify and trust the parties they are sending money to through their choice of methods.
Bitcoins are issued according to rules agreed to by the majority of the computing power within the Bitcoin network. The core rules describing the predictable issuance of Bitcoins to its verifying servers, a voluntary and competitive transaction fee system and the hard limit of no more than 21 million BTC issued in total.
Bitcoin does not require a central bank, State, or incorporated backers.
In the history of Bitcoin, there have been a few incidents, caused by problematic as well as malicious transactions. In the worst such incident, and the only one of its type, a person was able to pretend that he had a practically infinite supply of Bitcoins, for almost 9 hours.
Bitcoin relies, among other things, on public key cryptography and thus may be vulnerable to quantum computing attacks if and when practical quantum computers can be constructed.
If multiple different software packages, whose usage becomes widespread on the Bitcoin network, disagree on the protocol and the rules for transactions, this could potentially cause a fork in the block chain, with each faction of users being able to accept only their own version of the history of transactions. This could influence the price of Bitcoins.