Bitcoin is a cryptocurrency and worldwide payment system.[10]:3 It is the first decentralized digital currency, as the system works without a central bank or single administrator.[10]:1[11] The network is peer-to-peer and transactions take place between users directly, without an intermediary.[10]:4 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[12] and released as open-source software in 2009.[