Ever since Tokyo-based bitcoin exchange Mt. Gox filed for bankruptcy in February 2014, investigators have been puzzled by the disappearance of virtual currency worth hundreds of millions of dollars from its digital vaults.
Mt. Gox, which claimed it once hosted around 80 percent of bitcoin trading worldwide, closed in 2014 after admitting that 850,000 coins — worth around $480 million at the time — had disappeared from its vaults. Former CEO Mark Karpeles blamed the loss on hackers.
Karpeles later claimed he had found some 200,000 of the lost coins in a "cold wallet" — a storage device, such as a memory stick, that is not connected to computers. And yet investigators were never able to trace the remaining 650,000 missing coins.