Steven J. Murdoch and Robert N. M. Watson
Abstract. In this paper we explore the tradeoffs between security and performance in anonymity networks such as Tor. Using probability of path compromise as a measure of security, we explore the behaviour of various path selection algorithms with a Tor path simulator. We demon- strate that assumptions about the relative expense of IP addresses and cheapness of bandwidth break down if attackers are allowed to purchase access to botnets, giving plentiful IP addresses, but each with relatively poor symmetric bandwidth. We further propose that the expected la- tency of data sent through a network is a useful performance metric, show how it may be calculated, and demonstrate the counter-intuitive result that Tor's current path selection scheme, designed for performance, both performs well and is good for anonymity in the presence of a botnet- based adversary.
PETS 2008 presentation (Given by Steven Murdoch).