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Title: Privacy on the Line
Authors: Whitfield Diffie and Susan Landau
Publisher: The MIT Press
Copyright: 1998
ISBN: 0-262-04167-7
Pages: 342
Price: $25.00
Rating: 89%
Privacy on the Line, co-authored by Whitfield Diffie and Susan Landau, is one of those rare books that comprehensively summarizes and extends debate on an issue: in this case, the politics of wiretapping and encryption. While there are some editor ial flaws and a definite slant to the authors' views on their subject matter, the book is a valuable addition to the discussion on the technical and political aspects of telecommunications and data privacy.

Probably the most outstanding feature of Privacy on the Line is the authors' discussion of "national security", which I put in quotes because the concept has had so many elements added to it over the years that it's almost become meaningless. Howe ver, Landau and Diffie make an excellent choice by concentrating on the intelligence gathering aspect of national security; one always needs to know what potential adversaries are up to.

Wiretapping is a powerful intelligence gathering tool, allowing listeners to overhear and record conversations without alerting the participants. Wiretapping significantly lessens the danger to investigators, but it also represents a potentially enormous threat to individual liberty because of the technique's indetectability. Court orders permitting wiretaps may only be issued after investigators demonstrate probable cause and that all other means of evidence gathering have been attempted, but the techn ique has a history of abuse. The authors detail how J. Edgar Hoover built dossiers on political rivals (including one Senator who wanted to hold hearings on FBI surveillance activities), the Kennedy administration snooped on staffers' and journalists' co nversations when events in the Dominican Republic went against the president's wishes, and how wiretaps were used during the Watergate affair. It's worth noting that the last examples of abuse by federal authorities cited in Privacy on the Line we re in the mid-1970s, however.

Diffie and Landau tie wiretapping to the debate on escrowed encryption keys, a natural pairing as investigators would surely like to understand intercepted transmissions. Diffie, as befits the creator of public key cryptography, guides the reader through the basics of encryption and the work required to break various levels of security. On the policy level, the authors note the danger of escrowed encryption chilling free speech; since the government might be listening to any conversation, no conversatio n is safe. Combine that sentiment with the knowledge that the Justice Department has been pressuring phone companies to implement mechanisms allowing the government to listen to tens of thousands of conversations simultaneously and, whether justified or not, some commentators use the government's request to conjure visions of domestic intelligence gathering in the former Soviet Union and Eastern Europe.

Privacy on the Line is a well-conceived book with many outstanding parts, but the whole appears to suffer from the authors covering similar material in several places and not having the duplication resolved by the writers or their editorial staff. This criticism isn't meant to be overly harsh -- the final product is still worthy of high praise, but there were times, for instance, when I was reading Chapter 7 (Wiretapping) and thought I'd skipped back accidentally and was re-reading Chapter 6 (Priv acy: Protection and Threats).

In the end, though, Privacy on the Line's balanced description of the national security questions raised by wiretapping and encryption and subsequent opinionated but thorough policy analysis. It' s not quite a classic, but Privacy on the Line is a welcome addition to Agre and Rotenberg's Technology and Privacy in MIT's continuing examination of how technology affects the individual.

Curtis D. Frye (  is the editor and chief reviewer of Technology and Society Book Reviews.  He worked for four years as a defense industry analyst at The MITRE Corporation in McLean, VA, and is the author of Privacy-Enhanced Business, from Quorum Books.