Message-ID: <1487930694.1528.1.camel@mmci.uni-saarland.de>
From: Tim Ruffing <tim.ruffing@mmci.uni-saarland.de>
To: bitcoin-dev@lists.linuxfoundation.org
Date: Fri, 24 Feb 2017 11:04:54 +0100
In-Reply-To: <76fa5d76-6c54-e13e-7b55-a4409ef536f5@gmail.com>
References: <20170223181409.GA6085@savin.petertodd.org>
	<20170223212802.GA7608@savin.petertodd.org>
	<76fa5d76-6c54-e13e-7b55-a4409ef536f5@gmail.com>
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Subject: Re: [bitcoin-dev] SHA1 collisions make Git vulnerable to attakcs by
 third-parties, not just repo maintainers
Precedence: list

On Fri, 2017-02-24 at 00:57 +0100, Aymeric Vitte via bitcoin-dev wrote:
> 
> I have not worked on this since some time, so that's just thoughts,
> but maybe it can render things much more difficult
> than       computing two files until the same hash is found
> 

You basically rely on the idea that specific collisions are more
difficult to find. This trick or similar tricks will not help. (And
actually, the more files you add to the hash, the more freedom you give
the attacker.)

Even if certain collisions are more difficult to find today (which is
certainly true), the general rule is that someone will prove you wrong
in a year.

Even if ignore security entirely, switching to new hash function is
much simpler trying to fix the usage of a broken hash function.

Relying on SHA1 is hopeless. We have to get rid of it.

Best,
Tim