Patent ID: 8135129
Filing Date: 2012-03-13
Classification: G06F,H04L

Abstract:
1. A method for protecting a digital quantity contained in an integrated circuit over a first number of bits, in a calculation of modular exponentiation of data by said digital quantity, comprising: selecting, by the integrated circuit, at least a second number ranging between unity and the first number minus two; dividing, by the integrated circuit, the digital quantity into at least two portions, a first portion comprising, from the bit of rank zero, a number of bits equal to the second number, and a second portion comprising the remaining bits; calculating, by the integrated circuit, a first modular exponentiation of the data by the first portion of the digital quantity to provide a first result; calculating, by the integrated circuit, a first modular exponentiation of the data by the second portion of the digital quantity to provide a second result; calculating, by the integrated circuit, a second modular exponentiation of the second result by two raised to the power of the second number to provide a third result; and calculating, by the integrated circuit., the product of the first and third results of the modular exponentiations.