METHOD AND CIRCUIT FOR IMPLEMENTING A SUBSTITUTION TABLE

The invention concerns a method of implementing, by a cryptographic circuit (300), a substitution operation of a cryptographic algorithm based on a scrambled substitution table (302), the method comprising: performing, for each set of one or more substitution operations of the cryptographic algorithm, a series of sets of one or more substitution operations of which: one is a real set of one or more substitution operations defined by the cryptographic algorithm, the real set of one or more substitution operations being based on input data modified by a real scrambling key (SKEY); and one or more others are dummy sets of one or more substitution operations, each dummy set of one or more dummy substitution operations being based on input data modified by a different false scrambling key.