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

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Message-ID: <1481789755.1114.7.camel@gmail.com>
Date:   Thu, 15 Dec 2016 03:15:55 -0500
From:   Daniel Micay <danielmicay@...il.com>
To:     kernel-hardening@...ts.openwall.com,
        "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     hannes@...essinduktion.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        jeanphilippe.aumasson@...il.com, djb@...yp.to,
        torvalds@...ux-foundation.org, ebiggers3@...il.com
Subject: Re: [kernel-hardening] Re: [PATCH v2 1/4] siphash: add
 cryptographically secure hashtable function

On Thu, 2016-12-15 at 15:57 +0800, Herbert Xu wrote:
> Jason A. Donenfeld <Jason@...c4.com> 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.
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