Patent ID: 6914986

Claim:
A countermeasure method in an electronic component using a public key cryptography algorithm based on the use of elliptic curves in which a private key d and the number of points n on an elliptic curve are used to calculate a new deciphering integer d′ such that the deciphering of any message, by means of a deciphering algorithm, with d′ makes it possible to obtain the same result as with d, by performing the operation Q=d.P, where P is a point on the curve to which the scalar multiplication algorithm is applied, said method comprising the following steps: 1) taking a random value r with the same size as d; 2) calculating an integer d′ such that d′=d+r; 3) Performing a scalar multiplication operation whose result is a point Q′ on the curve such that Q′=d′.P; 4) Performing a scalar multiplication operation whose result is a point S on the curve such that S=r.P; and 5) calculating the point Q on the curve such that Q=Q′−S.