A test method comprising: acquiring a plurality of value sets (Ci), each value set comprising values of a physical quantity or of logic signals, linked to the activity of a circuit to be tested when the circuit executes an operation (OPRK) of an operation set of distinct cryptographic operations applied to a same data to be discovered, selecting at least two subsets (EC1i, EC2i) of values in each value set (Ci), for each value set, computing combined values (Wi) combining together one value in each value subset, for each value set, counting by a processing unit occurrence numbers of values transformed by a first surjective function applied to the combined values (Wi) 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 (g) of a part of the data to be discovered, computing by the processing unit a partial operation result, computing by the processing unit cumulative occurrence number sets obtained 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 data to be discovered, provide a partial operation result having a same transformed value resulting from the application of a second surjective function, and analyzing by the processing unit the cumulative occurrence number sets to determine the part of the data to be discovered, knowing that if the data to be discovered has leaked into the value sets, it is found in the cumulative occurrence number sets corresponding to the value of the part of the data to be discovered. acquiring a plurality of value sets (Ci), each value set comprising values of a physical quantity or of logic signals, linked to the activity of a circuit to be tested when the circuit executes an operation (OPRK) of an operation set of distinct cryptographic operations applied to a same data to be discovered, selecting at least two subsets (EC1i, EC2i) of values in each value set (Ci), for each value set, computing combined values (Wi) combining together one value in each value subset, for each value set, counting by a processing unit occurrence numbers of values transformed by a first surjective function applied to the combined values (Wi) 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 (g) of a part of the data to be discovered, computing by the processing unit a partial operation result, computing by the processing unit cumulative occurrence number sets obtained 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 data to be discovered, provide a partial operation result having a same transformed value resulting from the application of a second surjective function, and analyzing by the processing unit the cumulative occurrence number sets to determine the part of the data to be discovered, knowing that if the data to be discovered has leaked into the value sets, it is found in the cumulative occurrence number sets corresponding to the value of the part of the data to be discovered.