[Resource Topic] 2016/008: cMix: Mixing with Minimal Real-Time Asymmetric Cryptographic Operations

Welcome to the resource topic for 2016/008

Title:
cMix: Mixing with Minimal Real-Time Asymmetric Cryptographic Operations

Authors: David Chaum, Debajyoti Das, Farid Javani, Aniket Kate, Anna Krasnova, Joeri de Ruiter, Alan T. Sherman

Abstract:

We introduce cMix, a new approach to anonymous communications. Through a precomputation, the core cMix protocol eliminates all expensive realtime public-key operations — at the senders, recipients and mixnodes — thereby decreasing real-time cryptographic latency and lowering computational costs for clients. The core real-time phase performs only a few fast modular multiplications. In these times of surveillance and extensive profiling there is a great need for an anonymous communication system that resists global attackers. One widely recognized solution to the challenge of traffic analysis is a mixnet, which anonymizes a batch of messages by sending the batch through a fixed cascade of mixnodes. Mixnets can offer excellent privacy guarantees, including unlinkability of sender and receiver, and resistance to many traffic-analysis attacks that undermine many other approaches including onion routing. Existing mixnet designs, however, suffer from high latency in part because of the need for real-time public-key operations. Precomputation greatly improves the real-time performance of cMix, while its fixed cascade of mixnodes yields the strong anonymity guarantees of mixnets. cMix is unique in not requiring any real-time public-key operations by users. Consequently, cMix is the first mixing suitable for low latency chat for lightweight devices. Our presentation includes a specification of cMix, security arguments, anonymity analysis, and a performance comparison with selected other approaches. We also give benchmarks from our prototype.

ePrint: https://eprint.iacr.org/2016/008

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