Murder for hire, drug trafficking, embezzlement, money laundering—these might sound like plot points in a thriller, but they describe true stories from the short history of cryptocurrencies, the digital currencies like bitcoin that represent a completely new sort of financial transaction. Beyond this somewhat infamous reputation however, the technology that underlies cryptocurrencies, called blockchain, is hailed as the greatest advancement since the invention of the internet. This book explains that technology and reveals how it promises to make inroads into other core concepts of society, including identity, ownership, and even the rule of law.