When the virtual currency bitcoin was released, in January 2009, it appeared to be an interesting way for people to trade among themselves in a secure, low-cost, and private fashion. The Bitcoin network, designed by an unknown programmer with the handle “Satoshi ­Nakamoto,” used a decentralized peer-to-peer system to verify transactions, which meant that people could exchange goods and services electronically, and anonymously, without having to rely on third parties like banks. Its medium of exchange, the bitcoin, was an invented currency that people could earn—or, in Bitcoin’s jargon, “mine”—by lending their computers’ resources to service the needs of the Bitcoin network. Once in existence, bitcoins could also be bought and sold for dollars or other currencies on online exchanges. The network seemed like a potentially useful supplement to existing monetary systems: it let people avoid the fees banks charge and take part in noncash transactions anonymously while still guaranteeing that transactions would be secure.