Bitcoin is an unregulated, independent, decentralised virtual currency, thought to be impervious to fraud or theft and with no transaction fees.
It was invented - it's claimed - by the mysterious Satoshi Nakamoto in 2008.
Then last week an Australian computer scientist named Craig Wright, came forward claiming he was Satoshi.
But does it matter who invented Bitcoin? and what are the problems with cryptocurrencies? Listen to Billy Bambrough, City A.M.'s deputy news editor