Method and integrated circuit for carrying out a multiplication modulo m
First Claim
1. A method for carrying out a module M multiplication of two n-digit digital numbers (X, Y)—
- relative to a base m—
using an integrated circuit, where M<
mn;
X, y<
M, said method having the following method steps;
conventional created partial products I−
Xi*Y (0≦
I≦
n−
1) are formed, beginning with the most significant digit the partial product (I) is added (4) to a subtotal, which has been multiplied by m, in order to form a new subtotal the new subtotal is added (5) to one of a number of precalculated values (A), which are associated with size classes, in order to form a new subtotal the last n digits of the new subtotal are used for the addition (4) in the next iteration (I−
1) the new subtotal is approximately compared with the predetermined size classes in order to determine the size class into which the new subtotal falls the precalculated value (A) which belongs to the size class determined is used as a summand for the corresponding addition (5) in the next iteration (I−
1).
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Accused Products
Abstract
The invention relates to a method for carrying out a multiplication modulo M of two n-digit digital numbers (X, Y) in relation to a radix m by means of an integrated circuit. The inventive method consists of the following steps: conventionally determined partial products I=X<SB>1</SB>*Y(0=1=n−1), beginning with the highest-ranking place, are formed; the partial product (I) is added (4) to a subtotal multiplied by m, in order to form a new subtotal; the summands (S, C) of the new subtotal are added (5) to a value from a plurality of pre-calculated values (A) which are attributed to classes, in order to form a new subtotal; the new subtotal is used for the addition (4) of the next step (I−1); the new subtotal is approximately compared with the pre-determined classes in order to establish in which class the new subtotal falls; and the pre-calculated value (A) pertaining to the determined class is used as a summand for the corresponding addition (5) of the next step (i−1).
15 Citations
7 Claims
-
1. A method for carrying out a module M multiplication of two n-digit digital numbers (X, Y)—
- relative to a base m—
using an integrated circuit, where M<
mn;
X, y<
M, said method having the following method steps;
conventional created partial products I−
Xi*Y (0≦
I≦
n−
1) are formed, beginning with the most significant digitthe partial product (I) is added (4) to a subtotal, which has been multiplied by m, in order to form a new subtotal the new subtotal is added (5) to one of a number of precalculated values (A), which are associated with size classes, in order to form a new subtotal the last n digits of the new subtotal are used for the addition (4) in the next iteration (I−
1)the new subtotal is approximately compared with the predetermined size classes in order to determine the size class into which the new subtotal falls the precalculated value (A) which belongs to the size class determined is used as a summand for the corresponding addition (5) in the next iteration (I−
1). - View Dependent Claims (2, 3, 4, 5, 6, 7)
- relative to a base m—
Specification