Comparison Between Two Practical Mix Designs

  • Claudia Díaz
  • Len Sassaman
  • Evelyne Dewitte
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3193)


We evaluate the anonymity provided by two popular email mix implementations, Mixmaster and Reliable, and compare their effectiveness through the use of simulations which model the algorithms used by these mixing applications. Our simulations are based on actual traffic data obtained from a public anonymous remailer (mix node). We determine that assumptions made in previous literature about the distribution of mix input traffic are incorrect: in particular, the input traffic does not follow a Poisson distribution. We establish for the first time that a lower bound exists on the anonymity of Mixmaster, and discover that under certain circumstances the algorithm used by Reliable provides no anonymity. We find that the upper bound on anonymity provided by Mixmaster is slightly higher than that provided by Reliable.

We identify flaws in the software in Reliable that further compromise its ability to provide anonymity, and review key areas that are necessary for the security of a mix in addition to a sound algorithm. Our analysis can be used to evaluate under which circumstances the two mixing algorithms should be used to best achieve anonymity and satisfy their purpose. Our work can also be used as a framework for establishing a security review process for mix node deployments.


Active Attack Outgoing Message Entropy Source Passive Attacker Cryptographic Library 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • Claudia Díaz
    • 1
  • Len Sassaman
    • 1
  • Evelyne Dewitte
    • 1
  1. 1.K.U. Leuven ESAT-COSICLeuven-HeverleeBelgium

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