Abstract: Provided is a method for securing against fault attacks during verification a digital signature of a message on a client device. It performs (S1) at least one check on intermediate parameters that are generated for one that is different from 0 modulo n. It checks that values computed by several executions of the verification algorithm are the same, and checks that at least one mathematical relationship is verified. It performs a signature comparison final step to test equality between one of the intermediate parameters and a part of the digital signature. It triggers (S2) a fault attack countermeasure when at least one of the performed checks has failed.

Abstract: The present invention relates to a telecommunication system comprising: at least one subscriber station in the memory of which a secret key is stored, and authentication means for authenticating the subscriber station. In order to make the subscriber-station-specific secret key even more difficult to crack, the subscriber station checks the correctness of a received input by computing a message authentication code utilizing the input and a checking algorithm and computes a response to be transmitted to the authentication means by the subscriber station utilizing an authentication algorithm, the secret key stored in the memory of the subscriber station and the input if the input is correct on the basis of the message authentication code.