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Probabilistic Spying on Encrypted Tunnels

Talkat Black Hat USA 2014 · 2014-08-02..08-07· [security, networking]
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An open-source pacen toolkit trains on labeled pcaps and classifies encrypted tunnels by counting packet sizes in 10s windows, using modified decision trees (with optional Gaussian-mixture baselines). Training often needs ~12 hours of idle capture; evaluation returns probabilities and reaches 99.999% on Skype over SSH in their demo. It works with SSH or OpenVPN pcaps, is fast to train/classify, and the recommended defense is constant-size padding plus fixed-interval sending to remove the size/timing side channel.

AI-written summary · about

  1. 0:00Start
  2. 3:10Expectation-Maximization Algorithm
  3. 8:23How Does It Work
  4. 11:29Classifiers
  5. 13:04Mixed Gaussians
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