Subject: Re: [kernel-hardening] Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function

From: Daniel Micay <[email-masked]>
Date: Thu, 15 Dec 2016 03:15:55 -0500

On Thu, 2016-12-15 at 15:57 +0800, Herbert Xu wrote:
> Jason A. Donenfeld <[email-masked]> wrote:
> > 
> > Siphash needs a random secret key, yes. The point is that the hash
> > function remains secure so long as the secret key is kept secret.
> > Other functions can't make the same guarantee, and so nervous
> > periodic
> > key rotation is necessary, but in most cases nothing is done, and so
> > things just leak over time.
> 
> Actually those users that use rhashtable now have a much more
> sophisticated defence against these attacks, dyanmic rehashing
> when bucket length exceeds a preset limit.
> 
> Cheers,

Key independent collisions won't be mitigated by picking a new secret.

A simple solution with clear security properties is ideal.