Tor: The Second-Generation Onion Router

We present Tor, a circuit-based low-latency anonymous communication service. This Onion Routing system addresses limitations in the earlier design by adding perfect forward secrecy, congestion control, directory servers, integrity checking, configurable exit policies, anticensorship features, guard nodes, application- and user-selectable stream isolation, and a practical design for location-hidden services via rendezvous points. Tor is deployed 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. An earlier paper in 2004 described Tor’s…