#BTC is the first decentralized cryptocurrency. Based on a free- market ideology, bitcoin was invented in 2008 by Satoshi Nakamoto, an unknown person. [5] Use of bitcoin as a currency began in 2009, [6] with the release of its open-source implementation. [7]: ch. 1 In 2021, El Salvador adopted it as legal tender. [4] It is mostly seen as an investment and has been described by some scholars as an economic bubble. [8] As bitcoin is pseudonymous, its use by criminals has attracted the attention of regulators, leading to its ban by several countries as of 2021.[9]