[Python-Dev] Hash collision security issue (now public)

Antoine Pitrou solipsis at pitrou.net
Sun Jan 1 17:09:23 CET 2012

On Sun, 01 Jan 2012 16:48:32 +0100
Christian Heimes <lists at cheimes.de> wrote:
> The talkers claim and have shown that it's too easy to pre-calculate
> collisions with hashing algorithms similar to DJBX33X / DJBX33A. It
> might be a good idea to change the hashing algorithm, too. Paul as
> listed some new algorithms. Ruby 1.9 is using FNV
> http://isthe.com/chongo/tech/comp/fnv/ which promises to be fast with a
> good dispersion pattern.

We already seem to be using a FNV-alike, is it just a matter of
changing the parameters?

> A hashing algorithm without a
> meet-in-the-middle vulnerability would reduce the pressure on a good and
> secure seed, too.
> > We need to fix this as far back as Python 2.6, and it would be nice if a
> > source patch was available that works on Python 2.5 -- personally I do
> > have a need for a 2.5 fix and if nobody creates one I will probably end
> > up backporting the fix from 2.6 to 2.5.
> +1
> Should the randomization be disabled on 2.5 to 3.2 by default to reduce
> backward compatibility issues?

Isn't 2.5 already EOL'ed?
As for 3.2, I'd say no. I don't know about 2.6 and 2.7.



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