The Study Of Performance Improvement On Tor Second Genetation Onion Router

With the rapid popularization and development of the internet, as well as global researchers' increasing focus on anonymity and privacy security,anonymous communication technology has gradually become the focus of attention. Researchers in the anonymous field also need to pay attention to the performance of anonymous systems under the premise that the privacy of the user's identity is not compromised. The Second Generation Onion Router(Tor) is not only an anonymous communication system that protects user identity privacy on the internet, but also the most popular anonymous privacy solutions. With the growing number of Tor users and the growing size of the Tor network, its performance requirements are getting higher and higher under the premise of ensuring user anonymity. Therefore, this paper mainly analyzes and evaluates the performance of Tor, puts forward the improved scheme of routing algorithm and the file breakpoint retransmission scheme in hidden web.In this paper, we first summarize the theoretical basis of Tor, including Tor's network architecture, cache queue structure, onion unit structure,anonymous principle, hidden services and directory server. Then we analyzed the source code in detail, studied the overall structure of the source code, the main function of each code module and the call relationship between modules. Based on the analysis of source code, we studed the improvement proposal and suggestion of routing algorithm proposed by academic circles in recent ten years, and summarized the improved routing algorithm.Secondly, we use the simulation tools of Shadow and TorPS to evaluate the performance of the current routing algorithm, the performance and anonymity of the algorithm are analyzed in the case of network congestion.Aiming at the performance problem of the current routing algorithm in the network congestion situation, an improved routing scheme (RTT-Tor) based on link round trip time is proposed. Finally, the performance improvement and possible anonymity impairment problem are verified by simulation experiments.Finally, we analyze the design principle of hidden web (Tor hidden service), and propose the scheme of file breakpoint re-transmission in hidden web of Tor (FBC-Tor). In the process of file transfer, if the file transmission is interrupted due to network failure or other reasons, after the next connection is successful, the user can continue uploading or downloading the remaining files, there is no need to upload or download from scratch.The scheme not only protects the identity privacy of the user and improves the performance of Tor, but also saves the user's time and improves the performance experience.