Design, Implementation, and Analysis of an Anonymity Network for Web Browsing

Various MIX-based systems offering anonymity for near real-time traffic have been operational. However, they did not deliver many quantitative results about performance, bandwidth overhead, or other issues that arise when implementing or operating such a system. Consequently, the problem of how to design and operate a MIX-based system such that it provides a good balance between usability, protection from attacks, and overhead is not well understood. In this paper, we present the design, implementation, and analysis of a MIX-based anonymity network for Web browsing that offers a high level of anonymity against an attacker and good end-to-end performance at a reasonable bandwidth overhead. We describe a novel way of operating the MIXes that maximizes the protection from traffic analysis attacks while minimizing the bandwidth overhead. We also look at some advanced options we have integrated into our system that either improve its performance and usability or that make it more resistant against sophisticated attacks. We deliver quantitative results about the performance of our system, which should help to give a better understanding of MIX networks.