A countermeasure method in an electronic component implementing an elliptical curve based public key cryptography algorithm. A new decryption integer d' is calculated such that the decryption of an encrypted message on the basis of a private key d and the number of points n of an elliptical curve provides the same result with d' as with d, by performing the operation Q=d*P, whereby P is a point of the curve. Four steps are employed in the calculation: 1) a security parameter s is determined, 2) a random number k ranging from 0-2.sup.s is drawn, 3) the integer d'd+k*n is calculated, and 4) Q=d'.P is calculated.