Salts are never public. You're assuming that the salt is obtained along with the hash, which may sometimes but not always be true. However, I did understate t

Salts are never public. You're assuming that the salt is obtained along with the hash, which may sometimes but not always be true. However, I did understate the usefulness of this method since I was assuming the attacker doesn't have the salt, which often may not be the case.