Importance

Loading Importance Indicators...

Abstract

The present invention proposes a method for executing a blinded modular exponentiation, based on a window method with a window size of k bits so using 2^k pre-calculated variables (Y_i=Xⁱ mod N for i=0 to 2^k−1), on input data X of n bits to obtain output data S of n bits, S=X^d mod N, where d is the exponent of size m bits and N is the modulus of n bits, comprising the steps of: •blinding the pre-calculated variables by a blinding value Bi being a pseudo-random variable of the size of the modulus (n bits) and lower than the modulus (Y_j=Y_i×B₁ mod N for i=0 to 2^k−1) •executing the modular exponentiation with the blinded pre-calculated variables, to obtain an intermediate result (A), •unblinding the intermediate result by a unblinding value C₁=(B₁^g)⁻¹ mod N where g equals the concatenation of m/k times the value “1” coded on k bits, to obtain the output data S.

Loading the Abstract Image...

First Claim