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R. Annessi:
"Lower-Latency Anonymity - Latency Reduction in the Tor Network using Circuit-Level Round-Trip-Time Measurements";
Supervisor: E. Weippl, M. Mulazzani; Information & Software Engineering Group, 2014.

With the tremendous increases in communication over the Internet, privacy issues have become
more and more important. In the interest of allowing people to communicate without reveal-
ing potentially identifying information, much research and effort has been put forth to develop
anonymous communication protocols, which became the technical basis for promoting freedom
of speech, achieving privacy, and overcoming censorship on the Internet. The most widespread
and well researched anonymity system is Tor, which achieves a reasonable balance between the
conflicting demands of performance and security.
Although both latency and throughput have been improved significantly in recent years, Tor
users still occasionally experience long and variable delays. Such delays are not only harmful for
interactive web users, who create the vast majority of connections in the Tor network, but they
also prevent altogether the use of real-time protocols, such as the Voice-over-Internet Protocol,
where a certain quality of service is indispensable.
In this thesis we find our means to decrease latency, the most important property from users´
perspective. In our approach, clients actively measure Round-Trip-Times (RTT) of circuits after
they have been established and drop slow circuits before they begin to be used. We conduct sev-
eral experiments on the live Tor network, to verify our assumption that the use of lightweight,
active RTT measurements can achieve latency improvements. Our results show that this ap-
proach achieves an improvement not only in latency, but also in throughput, and in anonymity.

Anonymity, Tor, Latency

http://publik.tuwien.ac.at/files/PubDat_237768.pdf