Towards efficient traffic-analysis resistant anonymity networks

Existing IP anonymity systems tend to sacrifice one of low latency, high bandwidth, or resistance to traffic-analysis. High-latency mix-nets like Mixminion batch messages to resist traffic-analysis at the expense of low latency. Onion routing schemes like Tor deliver low latency and high bandwidth, but are not designed to withstand traffic analysis. Designs based on DC-nets or broadcast channels resist traffic analysis and provide low latency, but are limited to low bandwidth communication. In this paper, we present the design, implementation, and evaluation of Aqua, a high-bandwidth anonymity system that resists traffic analysis. We focus on providing strong anonymity for BitTorrent, and evaluate the performance of Aqua using traces from hundreds of thousands of actual BitTorrent users. We show that Aqua achieves latency low enough for efficient bulk TCP flows, bandwidth sufficient to carry BitTorrent traffic with reasonable efficiency, and resistance to traffic analysis within anonymity sets of hundreds of clients. We conclude that Aqua represents an interesting new point in the space of anonymity network designs.