Measuring Information Leakage in Website Fingerprinting Attacks.

Tor is a low-latency anonymity system intended to provide low-latency anonymous and uncensored network access against a local or network adversary. Because of the design choice to minimize traffic overhead (and increase the pool of potential users) Tor allows some information about the client's connections to leak in the form of packet timing. Attacks that use (features extracted from) this information to infer the website a user visits are referred to as Website Fingerprinting (WF) attacks. We develop a methodology and tools to directly measure the amount of information about a website leaked by a given set of features. We apply this tool to a comprehensive set of features extracted from a large set of websites and WF defense mechanisms, allowing us to make more fine-grained observations about WF attack and defense mechanisms.