This book constitutes the thoroughly refereed post-proceedings of the 6th International Workshop on Privacy Enhancing Technologies, PET 2006, held in Cambridge, UK, in June 2006 co-located with WEIS 2006, the Workshop on the Economics of Information Security, and WOTE 2006, the IAVoSS Workshop On Trustworthy Elections.The 24 revised full papers presented were carefully selected from 91 submissions during two rounds of reviewing and improvement. The papers both from academia and industry present novel research on all theoretical and practical aspects of privacy technologies, as well as experimental studies of fielded systems. This book constitutes the thoroughly refereed post-proceedings of the 6th International Workshop on Privacy Enhancing Technologies, PET 2006, held in Cambridge, UK, in June 2006 co-located with WEIS 2006, the Workshop on the Economics of Information Security, and WOTE 2006, the IAVoSS Workshop On Trustworthy Elections. The 24 revised full papers present novel research on all theoretical and practical aspects of privacy technologies. Privacy for Public Transportation 1 Thomas S. Heydt-Benjamin, Hee-Jin Chae, Benessa Defend, and Kevin Fu Ignoring the Great Firewall of China 20 Richard Clayton, Steven J. Murdoch, and Robert N.M. Watson Imagined Communities: Awareness, Information Sharing, and Privacy on the Facebook 36 Alessandro Acquisti and Ralph Gross Enhancing Consumer Privacy in the Liberty Alliance Identity Federation and Web Services Frameworks 59 Mansour Alsaleh and Carlisle Adams Traceable and Automatic Compliance of Privacy Policies in Federated Digital Identity Management 78 Anna Squicciarini, Abhilasha Bhargav-Spantzel, Alexei Czeskis, and Elisa Bertino Privacy Injector Automated Privacy Enforcement Through Aspects 99 Chris Vanden Berghe and Matthias Schunter A Systemic Approach to Automate Privacy Policy Enforcement in Enterprises 118 Marco Casassa Mont and Robert Thyne One Big File Is Not Enough: A Critical Evaluation of the Dominant Free-Space Sanitization Technique 135 Simson L. Garfinkel and David J. Malan Protecting Privacy with the MPEG-21 IPMP Framework 152 Nicholas Paul Sheppard and Reihaneh Safavi-Naini Personal Rights Management Taming Camera-Phones for Individual Privacy Enforcement 172 Mina Deng, Lothar Fritsch, and Klaus Kursawe Improving Sender Anonymity in a Structured Overlay with Imprecise Routing 190 Giuseppe Ciaccio Selectively Traceable Anonymity 208 Luis von Ahn, Andrew Bortz, Nicholas J. Hopper, and Kevin O'Neill Valet Services: Improving Hidden Servers with a Personal Touch 223 Lasse erlier and Paul Syverson Blending Different Latency Traffic with Alpha-mixing 245 Roger Dingledine, Andrei Serjantov, and Paul Syverson Private Resource Pairing 258 Joseph A. Calandrino and Alfred C. Weaver Honest-Verifier Private Disjointness Testing Without Random Oracles 277 Susan Hohenberger and Stephen A. Weis A Flexible Framework for Secret Handshakes (Multi-party Anonymous and Un-observable Authentication) 295 Gene Tsudik, and Shouhuai Xu On the Security of the Tor Authentication Protocol 316 Ian Goldberg Optimal Key-Trees for Tree-Based Private Authentication 332 Levente Butty Tam Holczer, and Istvan Vajda Simple and Flexible Revocation Checking with Privacy 351 John Solis and Gene Tsudik Breaking the Collusion Detection Mechanism of MorphMix 368 Parisa Tabriz, and Nikita Borisov Linking Anonymous Transactions: The Consistent View Attack 384 Andreas Pashalidis and Bernd Meyer Preserving User Location Privacy in Mobile Data Management Infrastructures 393 Reynold Cheng, Ye Zhang, Elisa Bertino, and Sunil Prabhakar The Effects of Location Access Behavior on Re-identification Risk in a Distributed Environment 413 Bradley Malin and Edoardo Airoldi Author Index 431