From: Matthieu Moy <matthieu.moy@imag.fr>
Date: Tue, 29 Apr 2008 18:17:51 GMT
Subject: Re: About git and the use of SHA-1
Message-ID: <vpqwsmg7cfk.fsf@bauges.imag.fr>
In-Reply-To: <7f9d599f0804290859y6a579302m5db9f7f827b320a4@mail.gmail.com>

"Geoffrey Irving" <irving@naml.us> writes:

> Here's the standard scenario for a hash collision attack, with
> parties, A, B, and C:
>
> 1. C, the malicious one, computes the standard two pdfs with matching
> sha1 hashes.
> 2. C sends the valid pdf to B through a git commit, and B signs it with a tag.
> 3. C grabs the signature, and then forwards the "signed" commit to A,
> but substitutes the invalid pdf with the same hash.

Just to add my 2 cents, examples of this are available on the web,
like:

http://th.informatik.uni-mannheim.de/People/Lucks/HashCollisions/

Same size, same hash. But that's with md5, not sha1.

-- 
Matthieu