[105646] in cryptography@c2.net mail archive
Re: Password hashing
daemon@ATHENA.MIT.EDU (Leichter, Jerry)
Thu Oct 18 14:16:00 2007
Date: Mon, 15 Oct 2007 10:20:53 -0400 (EDT)
From: "Leichter, Jerry" <leichter_jerrold@emc.com>
To: Sandy Harris <sandyinchina@gmail.com>
cc: Cryptography <cryptography@metzdowd.com>
In-Reply-To: <c5528eee0710121747i200c53e4jaa1e433429627a39@mail.gmail.com>
| > ... What's wrong with starting
| > with input SALT || PASSWORD and iterating N times, ....
|
| Shouldn't it be USERID || SALT || PASSWORD to guarantee that if
| two users choose the same password they get different hashes?
| It looks to me like this wold make dictionary attacks harder too.
As others have pointed out, with a large enough salt, dictionary attacks
become impossible. But it's worth mentioning another issue: People's
userid's do change and it's nice not to have the hashed passwords break
as a result. (This is pretty counter-intuitive to users who change their
names, and a disaster if a large organization needs to do a mass renaming
and somehow has to coordinate a mass password update at the same time.)
-- Jerry
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