phc-discussions - Re: [PHC] Combining sliding window and bit-reversal

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Message-ID: <20140206151301.GA31515@openwall.com>
Date: Thu, 6 Feb 2014 19:13:02 +0400
From: Solar Designer <solar@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Combining sliding window and bit-reversal

On Thu, Jan 30, 2014 at 04:18:37AM +0000, Samuel Neves wrote:
> On 30-01-2014 03:34, Solar Designer wrote:
> >
> >> By definition only the most significant bit of each byte is looked at in
> >> PSHUFB, so it's OK to share the same selection mask. I've additionally
> >> used PSHUFB to compute the bit reversal of 4-bit values, which should be
> >> somewhat faster. Here it is:
> >
> > Thanks!  Compared to yours, my SSSE3 code looks naive.
> >
> > This is in the public domain, correct?  (My bitrev.c is.)
> 
> Correct. I've placed a cleaned up version at
> https://gist.github.com/sneves/8702353 with disclaimers and attributions.

Thanks!

I just found a similar algorithm in:

http://software.intel.com/sites/default/files/article/165685/clmul-wp-rev-2.01-2012-09-21.pdf

page 19.

Alexander