The paper introduces Tor, a second-generation Onion Routing system designed to enhance anonymity and security in TCP-based applications. Tor addresses limitations of the original Onion Routing design by incorporating features such as perfect forward secrecy, congestion control, directory servers, integrity checking, configurable exit policies, and support for location-hidden services via rendezvous points. The system operates on the real-world Internet, requires no special privileges or kernel modifications, and provides a reasonable balance between anonymity, usability, and efficiency. The authors describe their experiences with an international network of over 30 nodes and discuss open problems in anonymous communication. Tor's design aims to be deployable, usable, flexible, and simple, while addressing specific threats and attacks. The paper also covers the construction of circuits, relay cells, stream management, integrity checking, rate limiting, congestion control, and the integration of rendezvous points for location-hidden services.The paper introduces Tor, a second-generation Onion Routing system designed to enhance anonymity and security in TCP-based applications. Tor addresses limitations of the original Onion Routing design by incorporating features such as perfect forward secrecy, congestion control, directory servers, integrity checking, configurable exit policies, and support for location-hidden services via rendezvous points. The system operates on the real-world Internet, requires no special privileges or kernel modifications, and provides a reasonable balance between anonymity, usability, and efficiency. The authors describe their experiences with an international network of over 30 nodes and discuss open problems in anonymous communication. Tor's design aims to be deployable, usable, flexible, and simple, while addressing specific threats and attacks. The paper also covers the construction of circuits, relay cells, stream management, integrity checking, rate limiting, congestion control, and the integration of rendezvous points for location-hidden services.