Bitcoin is a digital asset and a payment system invented by Satoshi Nakamoto. Nakamoto introduced the idea on 31 October 2008 to a cryptography mailing list, and released it as open-source software in 2009. There have been several high profile claims to the identity of Satoshi Nakamoto; however, none of them have provided proof beyond doubt that back up their claims.
The system is peer-to-peer and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes and recorded in a public distributed ledger called the blockchain, which uses bitcoin as its unit of account. Since the system works without a central repository or single administrator, the U.S. Treasury categorizes bitcoin as a decentralized virtual currency. Bitcoin is often called the first cryptocurrency, although prior systems existed and it is more correctly described as the first decentralized digital currency. Bitcoin is the largest of its kind in terms of total market value.

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