It's not that keeping the salt seperate would be so hard, it's that it wouldn't buy you anything. A modern OS will protect the password hashes+salts together, so that even if a cracker gets the list of users, they've got nothing to work on. If you system gets so cornholed that the cracker can read the hashes, it's safe to assume that they can also get the salts.

The job of the salt is to prevent dictionary attacks, i.e. a precompiled list of passwords and possible hashes. You can think of the salt, then, as part of the hash itself.

What you're suggesting (and it's not a bad idea, just a really awkward one :-) is to effectively split the hash into two seperate pieces. If you did this it would actually make more sense to make each part half salt and half hash. Then store the two fragments independently, such that if one is compromised it doesn't mean doom for the other one. Trouble is, the two halves would have to be really different - different machine, different OS, different database, different admin password - just to be sure that a compromise on one wouldn't affect the other.

There's probably more mileage (and less heartache) in using a good, trutworthy crypt algorithm like MD5crypt or (better yet) bcrypt (as used in OpenBSD), whish uses Blowfish. And pick good passwords. The idea here is that the algo itself is such a swine that dictionary attacks are infeasible and brute-forcing a hash (even with the salt) takes too long to be practical.

In reply to Re: (Ovid) (2): Too Convenient Security? by n3dst4
in thread Too Convenient Security? by Ovid

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