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Message-ID: <20120321034139.GA28445@openwall.com>
Date: Wed, 21 Mar 2012 07:41:39 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: SSSE3 PSHUFB (was: AMD Bulldozer and XOP)
On Wed, Mar 21, 2012 at 06:47:28AM +0400, Solar Designer wrote:
> BTW, I just realized how very powerful PSHUFB is. It's not just a
> shuffle. It's 16 parallel 4-to-4 array lookups, usable e.g. for 16
> parallel S-box lookups. It could even compete with bitslice DES, or
> even if it'd lose to bitslice DES in terms of speed, it could allow for
> a very fast non-bitslice DES or 3DES implementation, where we readily
> have 8 6-to-4 S-box lookups (or 32 4-to-4 lookups) to make in just one
> instance. It would be usable e.g. to encrypt just one data stream
> sequentially while meeting an existing standard, where a bitslice
> implementation would not be usable (we have no such task in JtR
> currently, but I imagine that it'd be helpful e.g. in some IPSEC
> implementation). We could try it for DES and for Lotus5.
...and with XOP's VPPERM or _mm_perm_epi8(), we can do 16 5-to-8 lookups
per instruction.
Alexander
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