Resisting Traffic Analysis on Unclassified Networks

While the need for data and message confidentiality is well known, the need to protect against traffic analysis on networks, including unclassified networks, is less widely recognized. Tor is a circuit-based low-latency anonymous communication service that resists traffic analysis. This second-generation Onion Routing system adds to the first-generation design with perfect forward secrecy, congestion control, directory servers, integrity checking, variable exit policies, and a practical design for rendezvous points. Tor works on the real-world Internet, requires no special privileges or kernel modifications, requires little synchronization or coordination between nodes, and provides a reasonable tradeoff between anonymity, usability, and efficiency.