(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
given that SHA1 was demonstrated to have alarming short-falls, and given
that the only remaining FIPS alternative, SHA-2, was in the same family
having a very similar design to SHA-1, it was a very understandable and
rational worry that SHA-2 might start to show cracks under the same kind of
attacks. (And that the attack against SHA1 (and method of attack) may
improve in effectiveness a bit also).
In that you see the selection of Keecak, focusing more on its high security
margin, and new defenses against existing known types of attacks.
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.
So while I am someone who pays attention to protocol, algorithm and
implementation efficiency, I am happy with Keecak. 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. And AMD 7970 GPU has 2048 cores. 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.
Adam
On Wed, Oct 03, 2012 at 01:05:10PM +0200, Eugen Leitl wrote:
----- Forwarded message from Sašo Kiselkov <skiselkov...@gmail.com> -----
From: Sašo Kiselkov <skiselkov...@gmail.com>
Date: Wed, 03 Oct 2012 08:22:26 +0200
To: "<z...@lists.illumos.org>" <z...@lists.illumos.org>
Subject: [zfs] SHA-3 winner announced
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:7.0.1) Gecko/20110929
Thunderbird/7.0.1
Reply-To: z...@lists.illumos.org
Hi All,
As many of you are probably aware, NIST has just announced the SHA-3
winner: Keccak. Wonderful, so now we can go ahead and implement it in
ZFS as the next-gen hash algo for dedup, right? Sadly, no. As I
predicted, NIST could, and it seems did, choose a candidate that fits
their criteria, not ours.
Keccak, you see, is slow. Mighty slow. It's comparable to and at times
even slower than the current SHA-2. See:
http://bench.cr.yp.to/graph-sha3/1536-thumb.png
Of course, I already hear people object: "But, it'll become faster once
we get hardware implementations!"
Sadly, no. Here are a few reasons why the "HW FTW!" argument is invalid:
1) x86 currently lacks even an implementation of SHA-2, which is over
a decade old, so I do not expect SHA-3 to come along any time soon.
2) The UltraSPARC T2 and higher are currently the only CPUs capable of
running Illumos that also have the algo in hardware and they got the
capability after 6 years from the release of the algorithm (and
Illumos doesn't even support that, but that's another story). Even
considering an optimistically fast design cycle, I don't expect
SHA-3 to appear in SPARC before the T6 (considering the T5 is slated
for release pretty soon, so feature additions to the silicon are
currently highly unlikely), which is on track for release in
2013/2014. My personal guess is that it's more likely to appear in
the next release cycle after the T6, some time in 2014 or 2015.
3) Illumos runs on a wide variety of platforms, most of which will
probably never get SHA-3 in hardware for the foreseeable future.
I know I'm going to get a lot of flack for saying so, but the hard
reality is that SHA-3 is over and that they've chosen an algorithm
that's essentially useless to ZFS. Sure it has a nice security margin,
much better than SHA-2, but we were already happy with the security
margin we had before, so what we wanted next is more speed, and sadly,
that's not something Keccak improves on.
In conclusion, I'd like to propose a course of action: mainline one (or
multiple) of the algorithms which I submitted patches for: Edon-R, BMW
or Skein. All of them have a security margin that's better than SHA-2
and much, much better performance.
Cheers,
--
Saso
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