A Dynamic Selection Algorithm of Tor Relay Based on Client Bias

Tor network is one of the most widely used low latency anonymous communication systems. To balance the network load, the Tor network uses an adjusted bandwidth weighted random selection algorithm to uniformly select relays of a circuit. A client can not adjust the bias of the relays during the circuit establishment process. However, the client's different requirements for network anonymity and performance may affect the further extension of Tor. This paper proposes a relay dynamic selection algorithm that allows the client to set the relay preference when establishing a circuit. The algorithm defines a dynamic parameter that can be adjusted by the client. Defining different dynamic parameters can realize the degree of bias for high-bandwidth relay or low-bandwidth relay during circuit establishment. The proposed algorithm is implemented in the Tor source code and the homogeneous network and heterogeneous network are respectively deployed on the Shadow simulation platform for experiments. Based on the simulation results, we have observed that setting different dynamic parameters can achieve partial improvement of network performance or network anonymity.