Re: [gentoo-dev] (crazy?) proposal to reduce load and disk on mirrors

[Robin H.Johnson <robbat2@gentoo.org>]

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On Tue, Jul 22, 2003 at 11:42:26PM -0700, Fred Van Andel wrote:
> As for the security of MD5, there is no published instance of anyone 
> finding 2 different datasets that produce an identical hash value. MD5 
> is a 128 bit hash algorithm so in theory it would be be required to 
> calculate approximately 1.2 * sqrt(2^128) different hashes in order to 
> have a 50% chance of a single collision. That would require > 350 
> billion gigabytes just to store the hashes. I believe MD5 to be secure 
> enough for this application.
I'd be VERY careful with this.
http://www.rsasecurity.com/rsalabs/faq/3-6-6.html

I've seen much more recent research into it myself, along with a way of
making it SIGNIFICENTLY more difficult to break.

Namely, store the correct filesize along with the MD5 sum in a
verifiable fashion. Having file containing a list of tarballs and their
sizes, then providing a GPG signature for that file makes solves the
issue to a level such that even all the computers in the world in 10
years could not beat it [famous last words, after seeing the
crypto-attack on RSA keys using a massive NFS setup].

-- 
Robin Hugh Johnson
E-Mail     : robbat2@orbis-terrarum.net
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