Bitcoin (Ƀ) is a cryptocurrency, a form of electronic cash. It is the world's first decentralized digital currency, and it was designed to work without a central bank or single administrator.Bitcoins are sent from user to user on the peer-to-peer bitcoin network directly, without the need for intermediaries.:4,5 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 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. 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.The following are frequently cited as bitcoin's positive characteristics: independence from world governments, banks and corporations no central authority to censor or interfere with transactions like gold, can act as a hedge against stocks and fiat currenciesrelatively low cost and fast peer-to-peer transactions between people regardless of geographic locationThe following are frequently cited as bitcoin's negative characteristics: behaves like an economic bubble wastefully high electricity usage causing great environmental damage no inherent value not backed by any government extensive use in illicit activity.