The telegraph, telephone, radio, and especially the computer have put everyone on the globe within earshot— at the price of our privacy. It may feel like we're performing an intimate act when, sequestered in our rooms and cubicles, we casually use our cell phones and computers to transmit our thoughts, confidences, business plans, and even our money. But clever eavesdroppers, and sometimes even not-so-clever ones, can hear it all. We think we're whispering, but we're really broadcasting.

A potential antidote exists: cryptography, the use of secret codes and ciphers to scramble information so that it's worthless to anyone but the intended recipients. And it's through the magic of cryptography that many communications conventions of the real world — such as signatures, contracts, receipts, and even poker games — will find their way to the ubiquitous electronic commons. But as recently as the early 1970s, a deafening silence prevailed over this amazing technology. Governments, particularly that of the United States, managed to stifle open discussion on any aspect of the subject that ventured beyond schoolboy science. Anyone who pursued the fundamental issues about crypto, or, worse, attempted to create new codes or crack old ones, was doomed to a solitary quest that typically led to closed doors, suddenly terminated phone connections, or even subtle warnings to think about something else.