Re: optimized DES key setup

Alex Alten (Alten@Home.Com)
Fri, 25 Sep 1998 22:56:51 -0700

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At 10:52 AM 9/24/98 GMT, Svend Olaf Mikkelsen wrote:
>>
>>I'll give numbers for my library, I've compiled everything using gcc under
>>linux, pentium pro 200. The key setup is always in C, the cipher speed
is for
>>encrypting 8 bytes in cbc mode. These numbers are only approximate, but
they
>>give a good approximation.
>>
>> set_key C asm cost
>>DES 4.830uS 2.658uS 1.709uS 14.5 bytes
>>3-DES 14.490uS 7.141uS 4.827uS 16.2 bytes
>
>This is fast, and I suppose more than adequate. Having made the key
>setup time = encryption time statement, I however looked at what
>assembler and larger tables can do.
>
>Using 4K tables in stead of 2K tables I was able to reduce the key
>setup time on a Pentium 120 to 3.7uS compared to 3.0uS for an
>assembler encryption on the same machine.

I just did some loop unrolling and also told the MSVC 5.0 compiler to generate
only pentium pro code. Now I'm clocking 5.7 usec/key on a Pentium Pro
200/NT 4.
I think I can squeeze a bit more speed out of this C code before I hit a wall.

- Alex

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Alex Alten
Alten@Home.Com
Alten@TriStrata.Com
P.O. Box 11406
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