[liberationtech] Paper on scalable dining cryptographers anonymity

[Bryan Ford]

Dear colleagues,

We would like to announce and solicit relevant feedback on a research paper we feel may be of interest to members of this list, on increasing the scalability of anonymous communication techniques that potentially could (though with many known caveats) offer resistance to traffic analysis attacks:

"Dissent in Numbers: Making Strong Anonymity Scale"
http://dedis.cs.yale.edu/2010/anon/papers/osdi12-abs

Abstract
Current anonymous communication systems make a trade-off between weak anonymity among many nodes, via onion routing, and strong anonymity among few nodes, via DC-nets. We develop novel techniques in Dissent, a practical group anonymity system, to increase by over two orders of magnitude the scalability of strong, traffic analysis resistant approaches. Dissent derives its scalability from a client/server architecture, in which many unreliable clients depend on a smaller and more robust, but administratively decentralized, set of servers. Clients trust only that at least one server in the set is honest, but need not know or choose which server to trust. Unlike the quadratic costs of prior peer-to-peer DC-nets schemes, Dissent's client/server design makes communication and processing costs linear in the number of clients, and hence in anonymity set size. Further, Dissent's servers can unilaterally ensure progress, even if clients respond slowly or disconnect at arbitrary times, ensuring robustness against client churn, tail latencies, and DoS attacks. On DeterLab, Dissent scales to 5,000 online participants with latencies as low as 600 milliseconds for 600-client groups. An anonymous Web browsing application also shows that Dissent's performance suffices for interactive communication within smaller local-area groups.

The source code for our experimental prototype is available at the Dissent project home page below, though please be advised that this prototype is still for experimental purposes only: it is a work in progress, its security is unlikely to be bulletproof at any given time, it is certainly not user-friendly, and it should not yet be considered deployable or even close to deployable by ordinary users.

Project home page: http://dedis.cs.yale.edu/2010/anon/

Bryan Ford
Yale University

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