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? > What I pointed out was that when a non-zero possibility of two data > blocks comparing as equal (even though they are no) exists, the method > in question should not be used for password data or other sensitive bits > of information. A larger hash key will never yield a possibility of > zero, so it doesn't mean that you can sleep untroubled at night while > the rsync server overwrites /etc/*pwd.db files periodically. 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. If, on the other hand, you're concerned about accidentally locking yourself out of the server as a result of an undetected mangling of the password database... you should be more worried about the server, and all your backups, being simultaneously hit by lightning. :-) Colin Percival _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-security To unsubscribe, send any mail to "[email protected]"