[cryptography] [zfs] SHA-3 winner announced

Eugen Leitl eugen at leitl.org
Wed Oct 3 09:41:27 EDT 2012


----- Forwarded message from Sašo Kiselkov <skiselkov.ml at gmail.com> -----

From: Sašo Kiselkov <skiselkov.ml at gmail.com>
Date: Wed, 03 Oct 2012 15:39:39 +0200
To: zfs at lists.illumos.org
CC: Eugen Leitl <eugen at leitl.org>
Subject: Re: [cryptography] [zfs] SHA-3 winner announced
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1

Well, it's somewhat difficult to respond to cross-posted e-mails, but
here goes:

On 10/03/2012 03:15 PM, Eugen Leitl wrote:
> ----- Forwarded message from Adam Back <adam at cypherspace.org> -----
> 
> From: Adam Back <adam at cypherspace.org>
> Date: Wed, 3 Oct 2012 13:25:06 +0100
> To: Eugen Leitl <eugen at leitl.org>
> Cc: cryptography at randombit.net, Adam Back <adam at cypherspace.org>
> Subject: Re: [cryptography] [zfs] SHA-3 winner announced
> User-Agent: Mutt/1.5.21 (2010-09-15)
> 
> (comment to Saso's email forwarded by Eugen):
> 
> Well I think it would be fairer to say SHA-3 was initiatied more in the
> direction of improving on the state of art in security of hash algorithms
> [snip]
> In that you see the selection of Keecak, focusing more on its high security
> margin, and new defenses against existing known types of attacks.

At no point did I claim that the NIST people chose badly. I always said
that NIST's requirements need not align perfectly with ZFS' requirements.

> If the price of that is slower, so be it - while fast primitives are very
> useful, having things like MD5 full break and SHA-1 significant weakening
> take the security protocols industry by surprise is also highly undesirable
> and expensive to fix. To some extent for the short/mid term almost
> unfixable given the state of software update, and firmware update realities.

Except in ZFS, where it's a simple zfs set command. Remember, Illumos'
ZFS doesn't use the hash as a security feature at all - that property is
not the prime focus.

> So while I am someone who pays attention to protocol, algorithm and
> implementation efficiency, I am happy with Keecak.

ZFS is not a security protocol, therefore the security margin of the
hash is next to irrelevant. Now that is not to say that it's entirely
pointless - it's good to have some security there, just for the added
peace of mind, but it's crazy to focus on it as primary concern.

> And CPUs are geting
> faster all the time, the Q3 2013 ivybridge (22nm) intel i7 next year is
> going to be available in 12-core (24 hyperthreads) with 30GB cache.  Just
> chuck another core at if if you have problems. ARMs are also coming out in
> more cores.

Aaah, the good old "but CPUs are getting faster every day!" argument. So
should people hold off for a few years before purchasing new equipment
for problems they have now? And if these new super-duper CPUs are so
much higher performing, why not use a more efficient algo and push even
higher numbers with them? If I could halve my costs by simply switching
to a faster algorithm, I'd do it in a heartbeat!

> And AMD 7970 GPU has 2048 cores.

Are you suggesting we run ZFS kernel code on GPUs? How about driver
issues? Or simultaneous use by graphical apps/games? Who's going to
implement and maintain this? It's easy to propose theoretical models,
but unless you plan to invest the energy in this, it'll most likely
remain purely theoretical.

> For embedded and portable
> use, a reasonably fast and energy frugal 32-bit or 64-bit processor is
> really cheap these days.  OK I know there's always a market for 8-bit
> processors, on the extreme cheap/low power end, but the validity of the cost
> complaint is diminishing even there.

My point in recommending a higher-speed hash is not for low-power
systems - these wouldn't even come near dedup for the foreseeable future.

Cheers,
--
Saso

----- End forwarded message -----
-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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