Whitfield Diffie and Susan Landau strip away the hype surrounding the policy debate over privacy 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. This updated and expanded edition revises their original–and prescient–discussions of both policy and technology in light of recent controversies over NSA spying and other government threats to communications privacy.