Ibis: An Overlay Mix Network for Microblogging

Ian Goldberg


Microblogging services such as Twitter are extremely popular. While they are commonly used by people who wish to reveal their names and friends to the world, some users, such as activists on the ground, may wish to be able to post without automatically revealing their identities or locations. An obvious approach is to use a low-latency anonymity system, such as Tor. However, low-latency systems fall prey to end-to-end timing attacks easily accomplished by an ISP or a government monitoring clients while also watching for posts to appear in real time on the microblogging site.

We present Ibis, a high-latency mix network designed specifically for microblogging. Ibis is an overlay network: the mix nodes can be microblogging clients that come online only sporadicly, and the intermediate encrypted messages are themselves posted as microblogged entries. We accomplish this through a novel cryptographic mix message format that uses only 47 bytes of overhead, while maintaining three-hop, 128-bit security against offline attack.

This is joint work with Paul Hendry.


Ian Goldberg is an Associate Professor of Computer Science and a University Research Chair 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 (now Radialpoint). His research currently focuses on developing usable and useful technologies to help Internet users maintain their security and privacy. He is a Senior Member of the ACM and a winner of the Early Researcher Award, the Outstanding Young Computer Science Researcher Award, and the Electronic Frontier Foundation's Pioneer Award.

Time and Place

Wednesday, September 18, 4:30pm
Gates 463A