Yes, I had the same thought. With a 10-digit pairing code, the security level against an online attack is 10^10 =~ 2^33. The attack is parallelisable - e.g. 2^16 cores doing 2^17 work each.
Should be fixable by exchanging hashes of the public keys before the keys themselves. Cheers, Michael Brian Warner <[email protected]> wrote: >On 8/22/14, 5:50 PM, Andy Isaacson wrote: > >> It seems a little silly to me too, but I'm encouraged to see new >> innovations in end user security systems, especially when they're not >> trying to do something fundamentally impossible and seem to have a >> reasonable grasp of what's required. > >Did anyone else get the sense that their "pairing code" is a truncated >hash of the session key, and thus vulnerable to the MitM forcing the two >session keys to achieve a partial collision of the codes? > >Sounds like a job for SAS[1] (Short Authenticated Strings). I haven't >thought through it too far, but I think speaking and verifying an 8 >digit code (4 from each side) would reduce the MitM's chance of success >down to 1-in-10k, no matter how much computation they spent trying for >collisions. SAS is unidirectional, so I think both sides have to emit >and compare a code (A->B + B->A), hence the 2x length requirement. But >maybe 1x is enough. > >cheers, > -Brian > >[1]: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.94.8504 >_______________________________________________ >Messaging mailing list >[email protected] >https://moderncrypto.org/mailman/listinfo/messaging _______________________________________________ Messaging mailing list [email protected] https://moderncrypto.org/mailman/listinfo/messaging
