From: Davide Brini <dave_br@...1278...>
Date: Fri, 23 Apr 2010 09:56:55 +0100
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Subject: Re: [Openvpn-devel] [PATCH] revocation
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On Friday 23 Apr 2010 00:34:38 Peter Stuge wrote:

> Davide Brini wrote:
> > the serial number is just an (almost) arbitrarily large number. Why
> > would a CA choose such a serial number?
> 
> In order to avoid a chosen-prefix collision that works among other
> things by predicting the serial number of certificates generated by
> the CA.
> 
> http://www.win.tue.nl/hashclash/rogue-ca/
> https://documents.epfl.ch/users/l/le/lenstra/public/papers/lat.pdf

Ah, that is interesting. I haven't seen an MD5 certificate in a long time, but 
I guess being safe doesn't hurt, as sooner or later SHA might become 
vulnerable as well (and people should start using the newer, longer 
SHA-256,etc. hashes anyway - not just for certificates).

Thanks!

-- 
D.