The hacking of the 2016 American election. The WannaCry ransomware attack on Britain’s National Health Service. The penetration of 500 million Yahoo accounts. The story of modern secrets is, in part, the story of the technology that protects them (or fails to). It’s the story of encryption, computer science, and cryptology, of the ever-increasing complexity of algorithms designed to shield information from prying eyes—and, seemingly inevitably, of their failure.