The Performance And Scalability Of Anonymous Communication System

With the rapid growth and public acceptance of the Internet as a means of communication and information dissemination, concerns about privacy and security on the Internet have grown. Anonymity becomes a essential requirement for many on-line Internet applications. Anonymity protects the identity of a participant in a networked application. In this dissertation, we mainly address the problem of how to get the high performance and efficiency in anonymous communication systems with better scalability. We research the analysis methord for anonymity, anonymous communication protocols and the tradeoff between performance and efficiency.Firstly, this dissertation gives a survey of researches of anonymous communication. Primary technologies used in typical anonymous communication systems are classified and analyzed. We also propose some open problems.In the main part of this dissertation, we research the problem of the performance of anonymous communication system, anaylze the effect of various factors such as rerouting path length, group size and proportion of compromised members to the anonymity and efficiency, and prove a quantitative equation for anonymity degree and these factors.Based on the result of theoretic analysis, we propose a new anonymous communication protocol with definite route length bound, which has a stronger anti-compromised capability than Crowds system with the same expected route length.As to the problem of rerouting delay, we put forward a newforwarding scheme, which implements short distance-prior forwarding. The new scheme is applied in random probability forward rerouting and definite path length rerouting algorithms. The results of theoretic analysis and simulation indicate that the new scheme can keep almost the same anonymity as typical ones and obviously decrease the forwarding delay.A new architecture for scalable anonymous communication system is also proposed in this dissertation. Using a distributed domain- managing scheme, different servers managing some members of the system, the new system can obviously decrease the cost of management. Both results of probability analysis and simulation show that the new system can keep almost the same anonymity degree with Crowds while scaling well in the large network environment.In this dissertation, we also propose a new anonymous protocol for multicast communication, which realizes anonymity for multicast sender and receiver. Using camouflage multicast addresses and multi-proxy forwarding technology, the new protocol improved the anonymity of sender and receiver for defending compromised proxy.Our research of the performance, efficiency and scalability for the anonymous communication will lay a significant theoretic basis for the practical application of anonymous systems in the large scale Internet.