METHOD OF TESTING THE RESISTANCE OF A CIRCUIT TO A SIDE CHANNEL ANALYSIS

The present invention relates to a test method of a circuit, comprising: acquiring a plurality of value sets comprising values of a physical quantity linked to the activity of a circuit to be tested when the circuit executes an operation of a set of distinct cryptographic operations applied to a secret data, selecting at least a first subset in each value set, for each value set, counting by a processing unit occurrence numbers of values transformed by a first surjective function applied to the values of the first subset of the value set, to form an occurrence number set for the value set, for each operation of the operation set, and each of the possible values of a part of the secret data, computing a partial operation result, computing cumulative occurrence number sets (CH) by adding the occurrence number sets corresponding to the operations of the operation set, which when applied to a same value or equivalent value of the possible values of the part of the secret data, provide a partial operation result having a same transformed value resulting from the application of a second surjective function, merging according to a selected merging scheme, cumulative occurrence numbers in the cumulative occurrence number sets (HT), and analyzing the merged cumulative occurrence number sets (HTR1) to determine the part of the secret data.