So I don't work for Tor, nor am I a graph theorist, but I'll add a few preliminary thoughts.
On 22 August 2013 21:08, Paul-Olivier Dehaye paul-olivier.dehaye@math.uzh.ch wrote:
As far as I can tell, the main threat by a global passive adversary comes from traffic analysis (?).
A Global Passive Adversary is technically outside of Tor's threat model (see https://trac.torproject.org/projects/tor/wiki/doc/TorFAQ#Whatattacksremainag...) - but if there are easy ways to make it more difficult for such an adversary, at a low engineering cost - then Tor tends to be up for them.
This attack should become easier as the number of Tor nodes increases (?)
I'm not sure I agree with that. If the adversary is not global, but only partly global, then network diversity is crucial. If the adversary is truely global, I don't think more nodes would help as much as more _traffic_.
A dual way to see this is that not enough mixing can happen around a node for incoming/outgoing edge pairs, bar injecting a huge amount of fake traffic.
In what sense do you use the word 'mixing'? In the traffic analysis literature, I think it tends to refer to mix networks, and collecting several messages into a pool before releasing some or all of them (http://crypto.is/blog/mix_and_onion_networks).
-tom