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From: Eric Biggers <ebiggers@kernel.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
	Theodore Ts'o <tytso@mit.edu>
Subject: Re: [PATCH v2] siphash: update the hsiphash documentation
Date: Thu, 21 Apr 2022 17:46:17 -0700	[thread overview]
Message-ID: <YmH62VkrJIvOAEQV@sol.localdomain> (raw)
In-Reply-To: <YmH5hDrUZKBymqYE@zx2c4.com>

On Fri, Apr 22, 2022 at 02:40:36AM +0200, Jason A. Donenfeld wrote:
> Hi Eric,
> 
> On Thu, Apr 21, 2022 at 05:27:31PM -0700, Eric Biggers wrote:
> > +On 64-bit kernels, the hsiphash functions actually implement SipHash-1-3, a
> > +reduced-round variant of SipHash, instead of HalfSipHash-1-3. This is because in
> > +64-bit code, SipHash-1-3 is no slower than HalfSipHash-1-3, and can be faster.
> > +Note, this does *not* mean that in 64-bit kernels the hsiphash functions are the
> > +same as the siphash ones, or that they are secure; the hsiphash functions still
> > +use an insecure reduced-round algorithm and truncate their outputs to 32 bits.
>  
> Small nit: "less secure" rather than "insecure", as I don't think
> there's a super realistic attack against 1-3. I can make that change
> when committing if that's fine by you.
> 
> Jason

That's fine, assuming that you're just talking about SipHash-1-3, not also
HalfSipHash-1-3.  The section title is "HalfSipHash - SipHash's insecure younger
cousin", so the word "insecure" is applied to HalfSipHash already.

- Eric

      reply	other threads:[~2022-04-22  0:46 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-22  0:27 [PATCH v2] siphash: update the hsiphash documentation Eric Biggers
2022-04-22  0:40 ` Jason A. Donenfeld
2022-04-22  0:46   ` Eric Biggers [this message]

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