Warren Moore <warren .
>holes that had been found in S/KEY. Can one of you point me to a source that
>covers/explains these holes, or simply tell me yourself?
S/key is vulnerable to authentication racing, in which you
try to log in faster than the victim, while sniffing their response.
There's a rough overview of it in my Internet attacks presentation,
at or around the end. Check:
It's easily enough fixed by making logging in an atomic
transaction so that a user can't be in the login process more than
once simultaneously -- which causes a potentially powerful denial
of service attack. The authentication racing attack works against
any authentication system that's not based on a challenge-response
or signature of a unique value.