George Danezis: Cryptography in Anonymous Communications

Anonymous communications have gained popularity both as a subject of academic research as well as being deployed and used by thousands of people. The protocols used hide who is communicating with whom using a mixture of cryptographic techniques, to make the content of the communication unlinkable, as well as traffic analysis counter-measures to disrupt information observers may extract from the timing and frequency of the traffic. This talk will present an overview of the cryptographic techniques used in theoretical as well as deployed mix and onion routing systems. The talk will be illustrated by concrete attacks that allow attackers to violate anonymity properties against hybrid cryptographic constructions as well as newer constructions based on universal re-encryption. Finally the open problems, of providing sound security definitions, as well as formal proofs for the security of anonymity related cryptographic constructions will be presented.

George Danezis is post-doctoral visiting fellow at the Cosic group, K.U.Leuven, in Flanders, Belgium. He has been researching anonymous communications, privacy enhancing technologies, and traffic analysis for the last 6 years, at K.U.Leuven and the University of Cambridge, where he completed his doctoral dissertation.

His theoretical contributions to the PET field include the established information theoretic metric for anonymity and the study of statistical attacks against mix systems. On the practical side he is one of the lead designers of Mixminion, the next generation remailer, and has worked on the traffic analysis of deployed protocols such as SSL and Tor. He was the co-chair of the Privacy Enhancing Technologies Workshop in 2005 and 2006, he serves on the PET workshop board and has participated in multiple conference and workshop program committees in the privacy and security field.