[tor-dev] Reduce RTT for preemptively built circuits (GSoC)

ra r_a at lavabit.com
Fri Jun 7 17:38:44 UTC 2013

Hello everyone!

During this year's Google Summer of Code I[0] will be working on reducing the 
Round-Trip-Time (RTT) for preemptively built circuits.[1] My mentors are Mike 
and Aaron.

A brief summary of the project:
RTTs of circuits can be measured by violating the exit policy of the exit node 
and the resulting error can be timed in a measuring client. It is assumed that 
the RTTs are Fréchet-distributed which could be used to reject a preemptively 
built circuit if its RTT is below a certain threshold value.
A basic algorithm will be implemented to gather the required data for further 
statistical analysis which should help answering open questions like:
• Are the RTTs Fréchet-distributed?
• Does this strategy make new attacks feasible?
• How many probes per circuit are needed to do reasonable estimations?
• How much additional load is added to the network?
• What is an appropriate cut-off percentile?
• Does the strategy work in terms of anonymity and performance?
• Does the RTT vary for destination ports? (This might be the case for 
destination ports that occur rarely in exit policies.)
• Does this strategy also work if guard nodes are congested?


[0] "ra_"  on OFTC
[1] http://www.google-melange.com/gsoc/project/google/gsoc2013/ra_/19001
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