I want to hash "user + password". EDIT: prehashing "user" would be an improvement, so my question is also for hashing "hash(user) + password". If cross-site same user is a problem then the hashing changed to hashing "hash(serviceName + user) + password" From what I read about salted hash, using "user + password" as input to hash function will help us avoid problem with reverse hash table hacking. The same thing can be said about rainbow table. Any reason why this is not as good as salted hashing?