ISSN 1000-1239 CN 11-1777/TP

Journal of Computer Research and Development ›› 2015, Vol. 52 ›› Issue (10): 2373-2381.doi: 10.7544/issn1000-1239.2015.20150562

Special Issue: 2015网络安全与隐私保护研究进展

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Towards Measuring Unobservability in Anonymous Communication Systems

Tan Qingfeng1,2,3, Shi Jinqiao1,2, Fang Binxing1,2, Guo Li1,2, Zhang Wentao1,2, Wang Xuebin1,2, Wei Bingjie4   

  1. 1(Institute of Information Engineering, Chinese Academy of Sciences, Beijing 100093);2(National Engineering Laboratory for Information Security Technologies (Institute of Information Engineering, Chinese Academy of Sciences), Beijing 100093);3(University of Chinese Academy of Sciences, Beijing 100049) ;4(National Computer Network Emergency Response Technical TeamCoordination Center of China, Beijing 100029)
  • Online:2015-10-01

Abstract: Anonymous communication technique is one of the main privacy-preserving techniques, which has been widely used to protect Internet users’ privacy. However, existing anonymous communication systems are particularly vulnerable to traffic analysis, and researchers have been improving unobservability of systems against Internet censorship and surveillance. However, how to quantify the degree of unobservability is a key challenge in anonymous communication systems. We model anonymous communication systems as an alternating turing machine, and analyze adversaries’ threat model. Based on this model, this paper proposes a relative entropy approach that allows to quantify the degree of unobservability for anonymous communication systems. The degree of unobservability is based on the probabilities of the observed flow patterns by attackers. We also apply this approach to measure the pluggable transports of TOR, and show how to calculate it for comparing the level of unobservability of these systems. The experimental results show that it is useful to evaluate the level of unobservability of anonymous communication systems. Finally, we present the conclusion and discuss future work on measuring unobservability in anonymous communication systems.

Key words: anonymous communications, relative entropy, unobservablity, privacy protection, traffic analysis

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