This is a fascinating account of the development of public key cryptography, from its origins in the minds of mathematicians and programmers to its inclusion in many modern software products. It is a long and torturous journey over the last thirty years from when encryption technology was the sole preserve of the government agencies such as the National Security Agency, to when the nature of modern developments such as the internet demanded more widely available encryption and prevented the Government from exercising a monopoly. The invention of public key cryptography is attributed to Whitfield Diffie and Martin Hellman. We are introduced to these pioneers as the narrative weaves together the discoveries, events and people that signpost the road to the eventual adoption of PKC.

"I arranged a half hour meeting at my office at Stanford," Marty Hellman now recalls, "figuring it's just not going to go anywhere, but what the heck." Thus was made the match that, in the world of crypto, would later attain the resonance of famous pairings elsewhere: Woodword - Bernstein. Lennon - McCartney. Watson - Crick. Diffie - Hellman.

Throughout the text Levy attempts to minimize the jargon necessary to render the story complete. The actual nuts and bolts of encryption technology are only mentioned in a fairly general way in order to probe the bigger issues of the political battles that would be fought once the technology itself evolved to a point where it exceeded the performance of the NSA's own encryption technology. This gives rise to the key conflict of the book. Firstly, in the development stages, a conflict between national security interests and academic freedom in the sense that academia was spawning technical papers whose contents paved the way to newer, more powerful forms of encryption. Secondly, that once such technology existed and was proven marketable, that it should be prohibited from export to enable the NSA to maintain its advantage in breaking codes. This faced several problems because of the nature of the internet in that restricting such technology to the United States was in all probability impossible anyway but also because software manufacturers had to limit the power of their built in encryption for their products bound for export. Thus the NSA, by classifying encryption technology as a form of munitions, could control its export.

Since 1994, he had been demanding publicly that if his agents were unable to get plaintext from their wiretaps, Congress should institute a new era of prohibition by banning unescrowed strong encryption. "the objective is to get those conversations, whether they're (conducted) by alligator clips or (by) ones and zeroes," he said.

Crypto is a compelling tale about the fertile soil of the information age, of the importance of ideas and not just the technology of their implementation, of the enormous repercussions of technology and its application and of the brave and sometimes thankless struggle of the men and woman who fought for their vision.