cMix: Mixing with Minimal Real-Time Asymmetric Cryptographic Operations

  • David Chaum
  • Debajyoti Das
  • Farid Javani
  • Aniket Kate
  • Anna Krasnova
  • Joeri De Ruiter
  • Alan T. Sherman
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10355)

Abstract

We introduce cMix, a new approach to anonymous communications. Through a precomputation, the core cMix protocol eliminates all expensive real-time 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 light-weight 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.

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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  • David Chaum
    • 1
  • Debajyoti Das
    • 2
  • Farid Javani
    • 3
  • Aniket Kate
    • 2
  • Anna Krasnova
    • 4
  • Joeri De Ruiter
    • 4
  • Alan T. Sherman
    • 3
  1. 1.Voting Systems InstituteLos AngelesUSA
  2. 2.Purdue UniversityWest LafayetteUSA
  3. 3.Cyber Defense LabUMBCBaltimoreUSA
  4. 4.Radboud UniversityNijmegenNetherlands

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