Date: Tue, 15 Jun 1999 16:27:30 +0930 (CST) From: Kris Kennaway <kkennawa@physics.adelaide.edu.au> To: Barrett Richardson <barrett@phoenix.aye.net> Cc: Holtor <holtor@yahoo.com>, freebsd-security@freebsd.org Subject: Re: DES & MD5? Message-ID: <Pine.OSF.4.10.9906151617560.1783-100000@bragg> In-Reply-To: <Pine.BSF.4.01.9906142309300.19480-100000@phoenix.aye.net>
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On Mon, 14 Jun 1999, Barrett Richardson wrote:
> > Hello guys. I've been using DES on all my servers
> > but i'm thinking of converting to MD5 since it
> > seems to be more secure?
MD5 passwords are believed to be much stronger than DES passwords: not only is
the keyspace larger (DES passwords only accept up to 8 characters, MD5 up to
2^64-1 characters :) but the algorithm itself is more resistant to attack. You
might have heard of the EFF's budget DES-cracking hardware they debuted last
year, which is capable of brute-forcing DES keys at a phenomenal rate, and
exhaustively searching the keyspace in a matter of a few days.
It's generally believed that MD5 passwords are much more resistant to attack,
although a weakness in the algorithm cannot be ruled out.
> > I know that its not an easy change, probably even
> > an impossible one...can anyone point me in a good
> > direction?
>
> You might could change the name of crypt in libdes.a to something
> like crypt_des() and then hack crypt() to fall back to crypt_des()
> if it does not get fed a salt beginning with "$1$".
Unfortunately, with the current crypt code it's not possible to have MD5
passwords when you have the DES libraries installed unless you hack crypt() in
libcrypt (if crypt() sees the availability of DES code it will use that in
preference to MD5). It's not hard to hack this to default the other way,
though. Then it would be a matter of expiring all your user passwords, and the
new ones they choose will be MD5 instead of DES.
I have some patches I'm working on with Mark Murray (based on some earlier
work by Brandon Gillespie) which provide 'unified' SHA-1/MD5/DES/Blowfish
password support, and can be configured to use different ciphers based on
login classes, but these are not quite ready for prime-time.
Kris
-----
"Never criticize anybody until you have walked a mile in their shoes,
because by that time you will be a mile away and have their shoes."
-- Unknown
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