RE: Twofish/AES News (bogus performance claims?)

Doug Whiting (DWhiting@Stac.com)
Fri, 4 Dec 1998 14:55:09 -0800

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Sorry for the confusion, Alex. The C performance numbers we used were the
'best' taken from the AES submissions themselves and any other place we
could find them. In particular, the 400 clocks/block number came from Brian
Gladman's C version, which he wrote to optimize for the Pentium Pro. The C
code we submitted to NIST did not run that fast; we spent our time
optimizing the assembly version. You can see Brian's tables and get his
code from:

http://www.seven77.demon.co.uk/aes.htm

I hope this clarifies things.

-----Original Message-----
From: Alex Alten
To: Doug Whiting
Sent: 12/4/98 9:48 AM
Subject: Re: Twofish/AES News (bogus performance claims?)

At 03:24 PM 12/3/98 -0600, Bruce Schneier wrote:
>There are some new papers on the Twofish webpage.
>
>We have improved our performance numbers. On Pentium-class machines,
key

I noticed you are claiming an encrypt of 400 cycles/block on a Pentium
Pro
200. This translates to 8 MB/sec enciphering speed. I tried your
optimized
C version and could only get 3 MB/sec (with a 128 bit key ECB mode). I
was
careful to ensure that the cipher worked with test data in a main memory
to
main memory encipherment. You are overstating TwoFish's real world
performance by a factor of about 2.5 . This makes me suspicious of your

assembler version speed claims, maybe it really runs at 760 c/block?

I used Microsoft MSVC 4.2. I set the optimizations for maximum speed and
to
emit Pentium Pro specific assembler code. I've included my test code
and a
slightly modified AES.h file, so that you can see for yourself how I
tested
it. I used your TWOFISH2.C AES submission code version 1.00, dated
April
1998.

- Alex

--
Alex Alten
Alten@Home.Com
Alten@TriStrata.Com
P.O. Box 11406
Pleasanton, CA  94588  USA
(925) 417-0159
 <<Aes.h>> 

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