One day in 1975, Whitfield Diffie greeted his wife at the door with the words "I think I've made a great discovery." Diffie, a brilliant, eccentric and somewhat paranoid M.I.T. graduate, had spent the past few years wandering around the U.S. in a beat-up Datsun 510 thinking about cryptography, the study of codes and ciphers. His discovery was a revolutionary technique called public key encryption that would rescue personal privacy in the Internet era by allowing data to be encoded quickly and easily. Steven Levy's meticulous Crypto: Secrecy and Privacy in the New Code War (Allen Lane; 356 pages) is the story of how he did it.
In '70s America virtually all information relating to cryptography was under the control of the National Security Agency. With the rise of the PC and then the Internet, libertarian-leaning computer hackers realized how easily the government could eavesdrop on their data and how important it was to get cryptography away from the Man and into the hands of the People. Diffie's breakthrough did just that. Throughout the '80s and '90s a ragtag group of like-minded crypto fiends built on his work and distributed it over the Internet, end-running the agency and ensuring that everyday citizens could keep their e-mail to themselves.
It's a great David-and-Goliath story-humble hackers hoodwink sinister spooks-but the complexity of the subject matter makes Crypto a slow read: encryption algorithms, export regulations and copyright wrangles, all of it crawling with abbreviations (when PKP takes on the nsa over RSA vs. the dsa, don't say we didn't warn you). Levy, the chief technology writer for Newsweek, has also chosen a difficult hero in Whit Diffie. For all his brilliance, the shy, secretive math geek remains a cipher.