Real time traffic over tor

Abstract

Anonymous censorship-resistant communication systems are primarily designed keeping in mind semi real-time traffic such as web browsing. One such system, Tor [1], has gained prominence as the de-facto anonymity preserving the censorship-resistant system and often used by journalists and whistle-blowers globally. It is however believed that proxy-based systems like Tor, that reroute traffic via circuitous paths, potentially incur unwanted latency for real-time applications like VoIP. Moreover, Tor supports only TCP at the transport layer, believed to make it even di cult to send real-time data (which depends on UDP). All the existing literature builds on this belief and has proposed various architectures built speci call for anonymous VoIP. However, no one has extensively and empirically quanti ed the above claims. Hence, in this project, we try to explore the performance of VoIP (measuring the PESQ and one-way delay) when sent over Tor with various controlled and Internet experiments. The results of these extensive experiments (about 1 million VoIP calls over the Internet) reveal contradictory results in comparison to the existing literature. These results show that anonymous VoIP calling is indeed possible on Tor with more than 80% calls above the PESQ of 3 (considered as good).