Andrew Bartlett wrote:
>               or else your users change from password1
> to password2 to password3 then back to password1.

        They sure do! I hate that...

        I spoke to my colleague, and he refreshed my memory
        about that part: we variously used crypt or an MD4
        hash to encrypt passwords and stored the encrypted
        form in a lookup table of N elements per user. If 
        someone changed their password, we encrypted it
        and looked to se if it was already there, and if not
        replaced the oldest stored copy.

        To avoid collisions with other people's
        passwords causing false positives, we generated 
        a salt from the userid, and applied it as part of 
        the encryption, but did not store the salt in the 
        lookup table so you couldn't see it was salted
        deterninistically from just looking at the 
        file.

--dave 
-- 
David Collier-Brown,           | Always do right. This will gratify 
Sun Microsystems DCMO          | some people and astonish the rest.
Toronto, Ontario               |
(905) 415-2849 or x52849       | [EMAIL PROTECTED]

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