Re: MD5 Collisions...
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On Tuesday 04 December 2007 09:40:58 am Eygene Ryabinkin wrote:
> Matt, good day.
>
> Tue, Dec 04, 2007 at 09:19:58AM -0500, Matt Piechota wrote:
> > Norberto Meijome wrote:
> >> I understand that the final nail in MD5's coffin hasn't been found
> >>
> > > yet ( ie, we cannot "determine the exact original input given a
> > > hash value") , but the fact that certain magic bytes can be found
> > > (rather quickly) so that any 2 given binaries end up as collisions
> > > seems , from my unlearned POV, more serious or sinister than what
> > > the text above implies.
> >
> > I think the big mitigating factor is that you can't easily generate a
> > message that has the same length as the original as well as the same
> > hash.
>
> No, read Kaminski's paper (http://www.doxpara.com/md5_someday.pdf):
> with Wong's and Joux's multicollision attack (or its extensions)
> one can generate files with the same sizes and MD5 hashes.
>
> The usefullness of this with application to the ports collection
> is questionable, since you should make two colliding archives and
> both of them should be unpackable and the second should do some
> evil things. But strictly speaking, there are attacks producing
> files with the same size and MD5 hash.
>
> http://www.cits.rub.de/MD5Collisions/ is also a good reading.
It's not really questionable....for all practical purposes it's worthless. =
In=20
order to generate meaningful same-length collisions you need control of the=
=20
original file. (Your links go to lengths to explain this...) In the case o=
f=20
a ports distfile if you have control of the original file you really don't=
=20
need to go to great lengths to generate collisions, you can simply toss you=
r=20
malicious content in there right from the get go.
=2D-=20
Thanks,
Josh Paetzel
PGP: 8A48 EF36 5E9F 4EDA 5A8C 11B4 26F9 01F1 27AF AECB
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