[37655] in bugtraq
Re: MD5 To Be Considered Harmful Someday
daemon@ATHENA.MIT.EDU (Steve Friedl)
Wed Dec 8 18:58:01 2004
Date: Wed, 8 Dec 2004 11:22:57 -0800
From: Steve Friedl <steve@unixwiz.net>
To: Joel Maslak <jmaslak@antelope.net>
Cc: Gandalf The White <gandalf@digital.net>, Dan Kaminsky <dan@doxpara.com>,
BugTraq <bugtraq@securityfocus.com>
Message-ID: <20041208192257.GA15067@linux.unixwiz.net>
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In-Reply-To: <Pine.LNX.4.56.0412071849110.4478@redsky.antelope.net>
On Tue, Dec 07, 2004 at 06:51:48PM -0700, Joel Maslak wrote:
> That can be a problem. It breaks non-repudiation - someone could create
> such a "swappable" contract and go to court and say "Yes, that's a valid
> signature, but I really signed *THIS* document which just happens to have
> an identical signature." Of course if I was called upon to testify, I
> would respond, "Yes, but it is clear this contract was written with the
> intent to defraud us, as to get this property, it has to be constructed in
> a very specific mind with this fraud in mind at time of contract
> origination..."
Bruce Schneier has long suggested that when signing a document made by
others, make some cosmetic changes to break any precomputed hash that
the creator might have in store for you.
Also: those who are not fully up to speed on the details of crypto hashes
might find my Tech Tip helpful:
An Illustrated Guide to Cryptographic Hashes
http://www.unixwiz.net/techtips/iguide-crypto-hashes.html
Steve
--
Stephen J Friedl | Security Consultant | UNIX Wizard | +1 714 544-6561
www.unixwiz.net | Tustin, Calif. USA | Microsoft MVP | steve@unixwiz.net
