The first great conflict over cryptography and state power happened in the 1990s. In one corner were cryptographers equipped with subtle math, digital technologies, and new ideas. In the other were the Clinton administration and its National Security Agency (NSA), which sought to maintain and extend the federal government’s control over cryptography. They struggled over the concept that cryptography could be classified as munitions, over requirements to include NSA-friendly chips in communication hardware, and, in general, over the shape of post–Cold War security.

The geeks eventually defeated the feds, freeing up crypto for public use. Cryptography became a huge force in business and private life, making ecommerce possible and enabling relatively secure interpersonal communication. At the same time, the rise of mobile devices and early social media raised new questions about privacy. In response, a “cypherpunk” movement arose, its name and attitude drawing on the cyberpunk subgenre of science fiction. Its proponents argued that only through personal use of encryption could individuals defend their right to communicate without interception.

Read the full review at