Security...

[edhall%rand-unix at sri-unix.UUCP]

UNIX `salts' its passwords with a 12-bit random number so that
identical plaintext has only a one-out-of-4096 chance of producing
the same cyphertext.  The first two characters of the encrypted
password represent this `salt'.  The salt is used to permute a
lookup table in the DES encryption algorithm.

Modifying the DES algorithm used for password encryption in this way
also keeps someone from making a fast password-search device using a
DES chip (unless the salt just happened to be that one-out-of-4096th
combination that corresponds to the actual DES standard; perhaps this
particular salt should be inhibited).

		-Ed