Tunnel length (WAS: Re: Tor sketches)

[Nick Mathewson]

On Wed, Apr 13, 2005 at 03:51:57PM -0700, Echo Nolan wrote:
> On approxiamately Tue, Apr 12, 2005 at 01:10:49PM -0400 , Nick Mathewson wrote:
> > Also please be aware: there is probably no security benefit to
> > changing your path length to anything higher than 3;
> Why not? It would seem to me that increasing path length would increase
> the strength of anonymity by increasing the number of keys that would
> need to be cracked/stolen. What attack defeats this?

End-to-end correlation attacks work if the attacker can view both ends
of a circuit.  The attacker notices that the timing and volume of
the traffic entering Alice's end of the circuit is correlated to the
timing and volume of the traffic leaving at Bob's end of the circuit,
and so links Alice to Bob.
 
-- 
Nick Mathewson
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