Research And Implementation Of Privacy-enhanced Low-latency Anonymous Communication Technology

Tor is a global ovlerlay network based on the Internet infrastructure and using anonymous communication mechanism and protocol,which can well conceal the communication relationship and protect the identities of both communication parties.Because it can enhance the anonymity of users' communication relationship and is easy to operate,it attracts many users who pay attention to the privacy protection of communication,however it also attracts the attention of many attackers,so there are more and more attacks against Tor network.In order to improve the security of Tor network,it is necessary to study the privacy enhancement technology of Tor network.At present,privacy enhancement technologies for Tor network mainly include traffic camouflage technology and secure link construction technology.The former changes Tor network traffic fingerprint information by adopting randomization and regular transformation,so as to avoid network censorship.Compared with the traffic camouflage technology,the secure link construction technology based on sensitive nodes and dangerous areas avoidance can enhance the security of Tor network more intuitively.However,there are two problems in the existing security link construction techniques: first,the identification of sensitive nodes and dangerous areas is not accurate enough;second,the traffic passing through the exit nodes will contain all the communication data of the users,which is easy to reveal the privacy of the users.Therefore,this thesis improves the existing privacy enhancement technology.The main work includes the following four aspects:Firstly,sensitive nodes avoidance method based on potential colluding nodes identification is designed.Above all,a coarse-grained recognition method based on link probability anomaly is proposed.By analyzing Tor relay connection protocol,the anomaly analysis of theoretical probability and actual probability of link construction is carried out then draw lessons from user association technology in social networks,extract key features from relay node attributes,design machine learning methods to analyze node similarity,and complete the identification and discovery of potential colluding nodes.At last,according to the identification results,design corresponding node avoidance technology.Secondly,a regional avoidance scheme based on AS path prediction is designed.By studying the AS path prediction algorithm based on path stitch technology,this thesis designs an improved Prob Infer path prediction algorithm.In the data preprocessing stage,the data processing flow is refined for AS loop data to improve the accuracy of the constructed AS topology information.Then analyze the selected feature information and optimize the features used for AS path prediction,finally improve the accuracy of path prediction algorithm.Based on the recognition result,the dangerous areas can be avoided accurately and quickly,so as to improve the protection effect of communication relationship.Thirdly,a multipath anonymous communication scheme based on weighted secret sharing is designed.Firstly,the communication mechanism of Tor access terminal is studied,then the data encoding/decoding scheme is designed based on(k,n)threshold secret sharing,and the multi-circuit weighted traffic scheduling algorithm is designed based on Tor flow control mechanism.Finally,the security analysis of multi-path anonymous communication scheme is carried out based on Tor network data.Finally,a low-latency anonymous communication system with enhanced privacy is implemented.Through the combination of potential colluding node identification and avoidance technology and dangerous area avoidance technology based on AS path prediction,the avoidance of sensitive nodes and dangerous AS areas is realized.Finally,an anonymous communication prototype system with enhanced privacy and low delay is realized based on secure link construction technology and anonymous communication technology of multipath transmission.To sum up,through the research and system implementation of privacy enhancement technology of Tor network,this thesis further enhances the protection effect of Tor anonymous network on user communication security,which can be applied to higher security application scenarios such as confidential communication.