Cryptographic method and cryptographic processor for carrying out the method

Abstract

A cryptographic processer and method for utilizing the "public key code" method of Rivest, Shamir, and Adleman ("RSA method"), for enciphering and deciphering messages wherein two large prime numbers, p and q, and a third large number, E are selected and multiplied to form, N=p*q, converting the message to be encrypted into a series of elements P.sub.i preferably of equal length and having numerical values less than that of N, encrypting these elements P.sub.i by raising each to the power E and subsequently reducing modulus N, to give the numbers C.sub.i =P.sub.i .sup.E modulus N, carrying out the above involution step by means of a series of multiplications, performing modulus-reduction operation following the series of multiplications, by carrying out a multiplication in the remainder class ring N, carrying out the aforesaid multiplication by breaking down the operation into individual steps, whereby the multiplication is essentially converted to a series of additions, and carrying out the aforesaid modulus-reduction as a series of subtractions, according to the classical division algorithm, wherein a first look-ahead technique is used for the division and the multiplication is also carried out with a second look-ahead technique.

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