A countermeasure method in a first electronic component communicating with a second electronic component uses a secret key K[0] cryptographic algorithm A of size k. The countermeasure implementation employs a systematic and regular evolution of K[i] by a function K[i]=f(k[i-1]), and transmission of i to the second component. A computational shortcut enables the second component to compute K[i] from K[0] without having to generate the i-1 keys K[1] to K[i-1] separating K[0] and K[i].