A year ago a hacker stole $55 million of a virtual currency known as ether. This is the story of the bold attempt to rewrite that history. ... Rather than moving bitcoin from one user to another, the ethereum blockchain hosts fully functioning computer programs called smart contracts—essentially agreements that enforce themselves by means of code rather than courts. That means they can automate the life cycle of bond payments, say, or ensure that pharmaceutical companies can authenticate the sources of their drugs. Yet smart contracts are also new and mostly untested. Like all software, they are only as reliable as their coding—and Gün was pretty sure he’d found a big problem. ... Gün feared the bug could allow a hacker to make unlimited ATM-like withdrawals from the millions, even if the attacker, who'd have needed to be an investor, had only $10 in his account. ... This staggering amount of money lived inside a program called a decentralized autonomous organization, or DAO. Dreamed up less than a year earlier and governed by a smart contract, the DAO was intended to democratize how ethereum projects are funded. Thousands of dreamers and schemers and developers who populate the cutting edge of computer science, most of them young, had invested in the DAO.