Anonymity networks protect people living under repressive regimes from surveillance of their Internet use. But the recent discovery of vulnerabilities in the most popular of these networks -- Tor -- has prompted computer scientists to try to come up with more secure anonymity schemes. At the Privacy Enhancing Technologies Symposium in July, researchers at MIT's Computer Science and Artificial Intelligence Laboratory and the École Polytechnique Fédérale de Lausanne will present a new anonymity scheme that provides strong security guarantees but uses bandwidth much more efficiently than its predecessors. In experiments, the researchers' system required only one-tenth as much time as existing systems to transfer a large file between anonymous users.

"The initial use case that we thought of was to do anonymous file-sharing, where the receiving end and sending end don't know each other," says Albert Kwon, a graduate student in electrical engineering and computer science and first author on the new paper. "The reason is that things like honeypotting" -- in which spies offer services through an anonymity network in order to entrap its users -- "are a real issue. But we also studied applications in microblogging, something like Twitter, where you want to anonymously broadcast your messages to everyone."

The system devised by Kwon and his coauthors -- his advisor, Srini Devadas, the Edwin Sibley Webster Professor of Electrical Engineering and Computer Science at MIT; David Lazar, also a graduate student in electrical engineering and computer science; and Bryan Ford SM '02 PhD '08, an associate professor of computer and communication sciences at the École Polytechnique Fédérale de Lausanne -- employs several existing cryptographic techniques but combines them in a novel manner.