Traffic Correlation on Tor by Realistic Adversaries
Aaron Johnson
US Naval Research Laboratory
SWS Colloquium
Aaron Johnson is a computer scientist at the U.S. Naval Research Laboratory.
A general theme of his research is designing protocols to provide good, provable tradeoffs between privacy and utility.
Specifically, he is working on private data publishing and anonymous communication protocols.
We present the first analysis of the popular Tor anonymity network that indicates the security of typical users against reasonably realistic adversaries in the Tor network or in the underlying Internet. Our results show that Tor users are far more susceptible to compromise than indicated by prior work. Specific contributions include
(1) a model of various typical kinds of users,
(2) an adversary model that includes Tor network relays, autonomous systems (ASes), Internet exchange points (IXPs), and groups of IXPs drawn from empirical study
(3) metrics that indicate how secure users are over a period of time,
(4) the most accurate topological model to date of ASes and IXPs as they relate to Tor usage and network configuration,
(5) a novel realistic Tor path simulator (TorPS), and
(6) analyses of security making use of all the above.
To show that our approach is useful to explore alternatives and not just Tor as currently deployed, we also analyze a published alternative path selection algorithm, Congestion-Aware Tor. We create an empirical model of Tor congestion, identify novel attack vectors, and show that it too is more vulnerable than previously indicated.