Bitcoin is a cryptocurrency and worldwide payment system.[8]:3 It is the first decentralized digital currency, as the system works without a central bank or single administrator.[8]:1[9] The network is peer-to-peer and transactions take place between users directly through the use of cryptography, without an intermediary.[8]:4 These transactions are verified by network nodes 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[10] and released as open-source software in 2009.[11]