On 2004-09-27 07:13, Colin Percival <[email protected]> wrote: > Giorgos Keramidas wrote: > >Increasing the number of bits the hash key uses will decrease the > >possibility of a collision but never eliminate it entirely, AFAICT. > > How small does a chance of error need to be before you're willing to > ignore it? That's a good question. I'm not sure I have a definitive answer, but the possibility of a collision is indeed scary. Especially since I haven't seen a study of the real probability of a collition is, given the fact that passwords aren't (normally) random binary data but a much smaller subset of the universe being hashed. > If an appropriately strong hash is used (eg, SHA1), then the probability > of obtaining an incorrect /etc/*pwd.db with a correct hash is much > smaller than the probability of a random incorrect password being > accepted. Remember, passwords are stored by their MD5 hashes, so a > random password has a 2^(-128) chance of working. I was probably being unreasonably paranoid about 'modified' passwords that don't get detected as modified, but what you describe is also true. _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-security To unsubscribe, send any mail to "[email protected]"