On 05/05/2012 03:05 PM, Ian Goldberg wrote: > On Sat, May 05, 2012 at 01:47:45AM +0200, Ondrej Mikle wrote: >> One trick I had in mind was create "secret hash function" (take the following >> with a grain of salt, algebra is not my "primary thing"): >> >> - you keep generators g_i secret, which turns the problem from discrete-log >> into >> a problem of finding n-th root in finite field (n is the value of the >> digraph, >> trigraph or few characters, e.g. encoded value of 'ec2bridge', possibly >> "blinded" by another multiplication with secret constant c_i) >> - in general, computing n-th root is quite slow [1], but there are many >> special >> cases like square root (quadratic residue) >> - the above properties would make it slow for attacker to brute-force all >> possible values - i.e. attacker can't just compute the result values of such >> homomorphic hash, because he doesn't know the function parameters (e.g. >> without >> computing the generators), but everyone can use the "homomorphic property" >> for >> testing parts > > It sounds like you're talking about the homomorphic hashing paper you > linked to in your last email. But there, the exponentiations are in > Z_p, and taking n-th roots in Z_p is totally trivial. > > I seem to have lost the thread of why we're doing this. Is it just to > count how many bridges are running our ec2 / rackspace / etc. bridge > images? Can't we just report that out of band? Is the EC2 IP space not > known? I must be missing something.
As I wrote before, the idea is over-engineered (I got a bit carried away; the EC2 IP space is known, it was an attempt to hide nicknames not on EC2 or similar cloud services potentially leaking information). Ondrej _______________________________________________ tor-dev mailing list [email protected] https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev
