Patent ID: 7822199
Filing Date: 2010-10-26
Classification: G06F,H04L

Abstract:
1. A method for performing a cryptographic operation in a device comprising an integrated circuit card under control of a security application, in which at least a part of a cryptographic value (y) is produced in the integrated circuit card, by a calculation utilizing a processor comprising at least one multiplication operation between a first (f 1 ) and a second (f 2 ) factor wherein one of said first and second factors includes a part that is a secret key (s) associated with the device, wherein said first factor (f 1 ) comprises a determined number of bits L in a first binary representation, wherein said second factor (f 2 ) comprises, in a second binary representation, several bits set to 1 with, between each pair of consecutive bits set to 1, a sequence of at least L−1 bits set to 0, the method comprising: obtaining a plurality (n) of successive binary versions of the first factor by shifting said first factor in accordance with the positions of the bits set to 1 of the second factor; carrying out the at least one multiplication operation by assembling said n successive binary versions of the first factor to produce said at least a part of the cryptographic value; and utilizing said at least part of the cryptographic value in a cryptographic exchange of information or a cryptographic security operation.