Telecommunication has never been perfectly secure, as a Cold War culture of wiretaps and international spying taught us. Yet many of us still take our privacy for granted, even as we become more reliant than ever on telephones, computer networks, and electronic transactions of all kinds. Whitfield Diffie and Susan Landau argue that if we are to retain the privacy that characterized face-to-face relationships in the past, we must build the means of protecting that privacy into our communication systems.Diffie and Landau strip away the hype surrounding the policy debate to examine the national security, law enforcement, commercial, and civil liberties issues. They discuss the social function of privacy, how it underlies a democratic society, and what happens when it is lost.