Paper 2014/621

(Nothing else) MATor(s): Monitoring the Anonymity of Tor's Path Selection

Michael Backes, Aniket Kate, Sebastian Meiser, and Esfandiar Mohammadi


In this paper we present MATor: a framework for rigorously assessing the degree of anonymity in the Tor network. The framework explicitly addresses how user anonymity is impacted by real-life characteristics of actually deployed Tor, such as its path selection algorithm, Tor consensus data, and the preferences and the connections of the user. The anonymity assessment is based on rigorous anonymity bounds that are derived in an extension of the AnoA framework (IEEE CSF 2013). We show how to apply MATor on Tor's publicly available consensus and server descriptor data, thereby realizing the first real-time anonymity monitor. Based on experimental evaluations of this anonymity monitor on Tor Metrics data, we propose an alternative path selection algorithm that provides stronger anonymity guarantees without decreasing the overall performance of the Tor network.

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Publication info
Published elsewhere. Major revision. 21st ACM Conference on Computer and Communications Security( CCS 2014)
TorTor path selectionProvable privacyAnonymity monitor
Contact author(s)
meiser @ cs uni-saarland de
2014-10-14: revised
2014-08-13: received
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      author = {Michael Backes and Aniket Kate and Sebastian Meiser and Esfandiar Mohammadi},
      title = {(Nothing else) {MATor}(s): Monitoring the Anonymity of Tor's Path Selection},
      howpublished = {Cryptology ePrint Archive, Paper 2014/621},
      year = {2014},
      note = {\url{}},
      url = {}
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