Walkie-Talkie: An Effective and Efficient Defense against Website Fingerprinting

Website fingerprinting is a traffic analysis attack that allows an eavesdropper to determine the web activity of a client, even if the client is using privacy technologies such as proxies, VPNs, or Tor. Effective defenses against website fingerprinting hamper user experience due to their large bandwidth overhead and time overhead, requiring more than a half minute to load a page on average. In this work we propose a new defense against website fingerprinting, Walkie-Talkie, with a small overhead that can confuse even a perfectly classifying attacker. Walkie-Talkie modifies the browser to communicate in half-duplex mode rather than the usual full-duplex mode, thus restricting the feature set available to the attacker. We then add random padding to further confuse the attacker. With Walkie-Talkie, at a bandwidth overhead of 32% and time overhead of 9%, the perfect attacker’s false positive rate exceeds 5%; at a bandwidth overhead of 55%, the perfect attacker’s false positive rate exceeds 10%. Our defense therefore allows webbrowsing clients to defend their privacy against website fingerprinting both effectively and efficiently.