linux-kernel - Re: [PATCH v2] siphash: update the hsiphash documentation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <YmH62VkrJIvOAEQV@sol.localdomain>
Date:   Thu, 21 Apr 2022 17:46:17 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v2] siphash: update the hsiphash documentation

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