A former crypto entrepreneur who was behind two digital currencies that collapsed and lost an estimated $40bn (29.9bn) has been sentenced by a New York judge to 15 years in prison for an "epic" fraud. Do Kwon, a South Korean national, was co-founder of Singapore-based Terraform Labs, which developed the TerraUSD and Luna digital coins. Kwon had admitted misleading investors about TerraUSD, a so-called stablecoin that was supposed to maintain its value against the US dollar. He was one of a number of crypto bosses to face charges in the US after digital tokens slumped in 2022, triggering the failure of several companies. US District Judge Paul A Engelmayer, who handed down the sentence, said the Stanford graduate had repeatedly lied to investors who trusted him with their money.