netdev - Re: [PATCH v5 1/4] siphash: add cryptographically secure PRF

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Message-ID: <CALx6S351VFRZmEQphRQy6YtmZYPnOtTN7=XiNrJmhWJGv4HUBg@mail.gmail.com>
Date:   Fri, 16 Dec 2016 11:47:35 -0800
From:   Tom Herbert <tom@...bertland.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Jean-Philippe Aumasson <jeanphilippe.aumasson@...il.com>,
        George Spelvin <linux@...encehorizons.net>,
        Andi Kleen <ak@...ux.intel.com>,
        David Miller <davem@...emloft.net>,
        David Laight <David.Laight@...lab.com>,
        Eric Biggers <ebiggers3@...il.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        kernel-hardening@...ts.openwall.com,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Netdev <netdev@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Theodore Ts'o" <tytso@....edu>, vegard.nossum@...il.com,
        "Daniel J . Bernstein" <djb@...yp.to>
Subject: Re: [PATCH v5 1/4] siphash: add cryptographically secure PRF

On Fri, Dec 16, 2016 at 4:39 AM, Jason A. Donenfeld <Jason@...c4.com> wrote:
> Hey JP,
>
> On Fri, Dec 16, 2016 at 9:08 AM, Jean-Philippe Aumasson
> <jeanphilippe.aumasson@...il.com> wrote:
>> Here's a tentative HalfSipHash:
>> https://github.com/veorq/SipHash/blob/halfsiphash/halfsiphash.c
>>
>> Haven't computed the cycle count nor measured its speed.
>
Tested this. Distribution and avalanche effect are still good. Speed
wise I see about a 33% improvement over siphash (20 nsecs/op versus 32
nsecs). That's about 3x of jhash speed (7 nsecs). So that might closer
to a more palatable replacement for jhash. Do we lose any security
advantages with halfsiphash?

Tom

> This is incredible. Really. Wow!
>
> I'll integrate this into my patchset and will write up some
> documentation about when one should be used over the other.
>
> Thanks again. Quite exciting.
>
> Jason