Re: 8-bit modular exponentiation code?
At 07:30 AM 5/24/03 +0100, Adam Back wrote: Colin Plumb's crypto library bnlib supports multiple word size I believe. On Fri, May 23, 2003 at 11:36:58AM -0700, Major Variola (ret.) wrote: Anyone know of any open-source modexp code for 8-bit cpus? Thank you for your response, however (for the record) that code requires at least a 16bit CPU. From bnlib.doc (an amusing read, BTW): It is written in C, and should compile on any platform with an ANSI C compiler and 16 and 32-bit unsigned data types Small is defined as less than 65536, the minimum 16-bit word size supported by the library.
Re: 8-bit modular exponentiation code?
On Fri, 30 May 2003, Major Variola (ret) wrote: On Fri, May 23, 2003 at 11:36:58AM -0700, Major Variola (ret.) wrote: Anyone know of any open-source modexp code for 8-bit cpus? Thank you for your response, however (for the record) that code requires at least a 16bit CPU. From bnlib.doc (an amusing read, BTW): It is written in C, and should compile on any platform with an ANSI C compiler and 16 and 32-bit unsigned data types Small is defined as less than 65536, the minimum 16-bit word size supported by the library. It can't be that hard to modify it to work with an 8 bitter. I've written an aweful lot of 40 bit floating point routines for everything from 6809's to PIC's. 8 bit modulus code should be easy. Patience, persistence, truth, Dr. mike
Re: 8-bit modular exponentiation code?
At 10:34 AM 5/30/03 -0700, Bill Frantz wrote: I think your best bet for an 8 bit CPU will be an assembly language routine. Likely so. For those interested, I found this article, which does in fact use enhanced (it has a multiplier) Z80 assembly, included in the article: http://www.ddj.com/documents/s=1030/ddj9309e/9309e.htm The Z80180 and Big-number Arithmetic Squeezing 512-bit operations out of 8-bit microcontrollers Burton S. Kaliski, Jr. For instance, in one recent project, our challenge was to implement 512-bit RSA private-key operations in less than 10 seconds on Zilog's 8-bit Z80180 microcontroller running at 10 million cycles/second. . The folks at cyphercalc.com have a cyphermath8 library, albeit commercial. See http://cyphercalc.com/math/features.htm They give this performance data for the Rabbit CPU (see http://cyphercalc.com/math/performance.htm) 780 milliseconds for a modular exponentiation with a 128-bit base, 40-bit exponent, and 128-bit odd modulus. Exponent ones density: 50%. Target: Rabbit Semiconductor RCM2020, running at 18.4Mhz. Compiled under Dynamic C, version 6.03, with assembly optimizations in effect. [no affiliation] . Smartcard vendors tend to include a modexp co-processor.
