Bill Gates, the co-founder of Microsoft, has criticised the anonymity of cryptocurrencies such as bitcoin, saying the use of digital cash has led to deaths.
The world's second richest man took part in a Reddit "Ask Me Anything" session this week, during which he was asked about his thoughts on cryptocurrency.
The technology has soared in popularity over the past year as the price of bitcoin climbed to nearly US$20,000 ($27,762) before falling back to trade at about US$10,400.
Part of the appeal of the digital cash is the anonymity it grants holders. It uses decentralised technology for secure payments and storing money that does not require banks or people's names.
But while that feature is lauded by some, Gates said it was not "a good thing".