On Tue, Feb 11, 2014 at 9:07 PM, Zack Weinberg zackw@panix.com wrote:
(3) Service transmits to Client:
{ E_b(Fs), E_b(Fg), E_b(F1), ..., E_b(Fn), F1, ..., Fn }_swhere Fs is the fingerprint of the service itself, Fg the fingerprint of the service's selected guard, and F1...Fn the fingerprints of the rendezvous candidates.
As far as I can tell, none of E_b(F1),...,E_b(Fn) is ever used again in the protocol. Is the only point to convince the client that F1,...,Fn are not Fs or Fg? Because you have a problem in that case: you need to convince the client that E_b(F1) is actually E_b(F1) and not E_b(Some other random junk). (E_b(F1) should be replaced by a zero-knowledge proof that E_b(Fs) != E_b(F1))
I also think that this protocol is immune to abort-if-you-don't-like-the-answer provided that each side imposes a substantial delay between connection attempts.
This sounds like a great way to DoS your least favorite hidden service at low cost.