In 2013 and 2014, the European Banking Authority[145] and the Financial Industry Regulatory Authority (FINRA), a United States self-regulatory organization,[146] warned that investing in bitcoins carries significant risks. Forbes named bitcoin the best investment of 2013.[147] In 2014, Bloomberg named bitcoin one of its worst investments of the year.[148] In 2015, bitcoin topped Bloomberg's currency tables.[149]

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[9] and released as open-source software in 2009.[10] Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,[11] 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.[12]