[tor-dev] Projects to combat/defeat data correlation

Moritz Bartl moritz at torservers.net
Thu Jan 16 04:02:26 UTC 2014

On 01/16/2014 04:16 AM, Jim Rucker wrote:
> There was a story in the news recently of a Harvard student who used Tor
> to send a bomb threat to Harvard in order to cancel classes so he
> wouldn't have to take a test. He was apprehended within a day, which
> puts into question the anonymity of Tor.

The way I understand it is that they did not exploit a weakness in any
system, they just (more or less) performed regular police work.

See https://www.schneier.com/crypto-gram-1401.html#3

> From my understanding (please correct me if I'm wrong) Tor has a
> weakness in that if someone can monitor data going into the relays and
> going out of the exit nodes then they can defeat the anonymity of tor by
> correlating the size and number of packets being sent to relays and
> comparing those that the packets leaving the exit nodes.

It is not that simple, but in principle you are correct. A good paper to
read about this is http://freehaven.net/anonbib/#ccs2013-usersrouted

See anonbib also for mitigations that were suggested and investigated
over time (which are not that easy either).

Moritz Bartl

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