Unlike paper money and gold, cryptocurrency doesn't physically exist, consisting of digital bits and bytes. Libertarians and cryptographer anarchists believe digital currency can wrest control of the financial system from banks and brokers. Paul Vigna and Michael Casey describe cryptocurrency as "a pure form of information technology, explicitly disruptive, a decentralised mechanism for society to judge the validity of monetary transactions". Bitcoin is the original, most accepted form of digital money. It's just six years old, going from "the pet project of a lonely coder" to "a global phenomenon", from worthless to valuable, its value rising and crashing on the money markets as belief in the bitcoin revolution ebbs and flows. In this comprehensive work the authors' research and their engagement with techies and entrepreneurs have convinced them of bitcoin's capacity to change the world. To what precise extent is still, like the identity of bitcoin's elusive founder, Satoshi Nakamoto, unknown.