Patent ID: 6298442
Filing Date: 2001-10-02
Classification: G06F,H04L

Abstract:
A method of cryptographically processing a message using an asymmetric cryptographic protocol involving a private key including a secret exponent, in a manner resistant to external detection of the secret exponent, comprising the steps of:(a) obtaining a digital quantity representative of at least a portion of said message, said digital quantity to be cryptographically processed using an asymmetric cryptographic protocol involving a private key including a secret exponent and an associated modulus;(b) transforming said exponent to an expanded representation thereof, said expanded representation including a sequence of symbols, each said symbol representing a modular multiplication;(c) loading an accumulator with a positive integer power of said digital quantity;(d) for each said symbol in at least a portion of said expanded representation:(i) multiplying, modulo said modulus, said value in said accumulator by a positive integer power of said digital quantity, said integer power being indicated by said symbol, and(ii) updating said accumulator with the result of said step (i),(iii) by executing a plurality of microprocessor instructions whose form is independent of the value of said symbol;thereby cryptographically processing said digital quantity in a manner resistant to external detection of said secret exponent.