Walking Onions: Scaling Anonymity Networks while Protecting Users - Talk by Ian Goldberg (University of Waterloo)


Forest Sciences Building (2424 Main Mall), Room 1001


Scaling anonymity networks offers unique challenges. Due to the distribution of trust on these networks, attackers can exploit differing views of the network's topology to perform epistemic and route capture attacks. Anonymity networks in practice, such as Tor, have opted for security over scalability by requiring participants to share a global, consistent view of all relays to prevent these kinds of attacks. Such an approach requires each user to download information about every relay, causing the total amount of data each user must download every epoch to scale linearly with the number of relays. As the number of clients increases, more relays must be added to provide bandwidth, further exacerbating the total load on the network.

In this talk, we present Walking Onions, a set of protocols improving scalability for anonymity networks by enabling constant-size scaling of the information each user must download in every epoch. Walking Onions offers the same security properties as current designs that require a global, consistent network view, while bounding the amount of data about the global state of the network each client must download.

This is joint work with Chelsea Komlo and Nick Mathewson.


Ian Goldberg is the Canada Research Chair in Privacy Enhancing Technologies. He is a Professor in the Cheriton School of Computer Science at the University of Waterloo, where he is a founding member of the Cryptography, Security, and Privacy (CrySP) research group. He holds a Ph.D. from the University of California, Berkeley, where he discovered serious weaknesses in a number of widely deployed security systems, including those used by cellular phones and wireless networks. He also studied systems for protecting the personal privacy of Internet users, which led to his role as Chief Scientist at Zero-Knowledge Systems, a Montreal-based startup.  His research currently focuses on developing usable and useful technologies to help Internet users maintain their security and privacy.  He is a Distinguished Member of the Association for Computing Machinery and a winner of the Outstanding Young Computer Science Researcher Award, the Electronic Frontier Foundation's Pioneer Award, the USENIX Security Test of Time Award, and the Caspar Bowden Award for Outstanding Research in Privacy Enhancing Technologies.

Host:  Dr. Tamara Munzner, UBC Computer Science

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