Two-and-a-half years after the collapse of Mt. Gox ushered in a multi-year bear market in the world of digital currencies, the trial of former Gox chief executive officer Mark Karpeles began Tuesday in Tokyo. Karpeles pleaded “not guilty” to charges of embezzlement and fraud stemming from the collapse of what was once the world’s most-active platform for buying and selling digital currencies. Some 850,000 bitcoins – then worth around half a billion U.S.