From: markh@wimsey.bc.ca (Mark C. Henderson)
Date: Fri, 26 Aug 94 09:01:58 PDT
To: cypherpunks@toad.com
Subject: Re: Fast modular exponentiation
Message-ID: <m0qe3cC-0000VhC@vanbc.wimsey.com>
MIME-Version: 1.0
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> But it is pretty unsatisfying to say that the best algorithm "depends" on
> half a dozen variables, and that we can't reliably predict (engineer) a
> solution.
It does seem to come down to that though.  I've spent a bit of time
playing with a couple of versions of Montgomery Mult code plus
other optimisations for modular exponentiation.

What works best depends upon the processor (I was doing C with some
inline assembler for the multiply and divide ops).

I remember that one particular approach worked very well on an
HP 9000/730 and was miserable on anything else I tried (Sparc, 80486,
MIPS R3000, 68030).

There's a really nice survey paper by Cetin Kaya Koc (then of RSADSI) 
called _High Speed RSA Implementation_ which describes various 
optimisations. The references in this are also pretty useful. 

Mark

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