There is most definately a system where the salt is kept separate to the hash - secret key crypto(logy|graphy). What you are saying is completely reasonable, since you are forcing an attacker to check every salt rather than supplying him with the right salt.

Even if the secret key is compromised, you have reverted to the usual security level - the attacker knows the salt, just like in a password file.

It is true that using different salts forces the attacker to use a pre-hashed dictionary 255 times larger, but advances in storage will take care of that soon enough.

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Jeremy
I didn't believe in evil until I dated it.