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 of an operation set of distinct cryptographic operations applied to a same data to be discovered; 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 results of at least two distinct partial operations (OPk) of the operation; selecting values in each value set for each partial operation of the operation; and for each value set and each partial operation of the operation corresponding to the value set, counting by a processing unit occurrence numbers of values transformed by a first surjective function (F1k) applied to the selected values (ECki) for the partial operation of the value set, to form an occurrence number set for the value set and for the partial operation; characterized in that it further comprises: computing by the processing unit for each partial operation result cumulative occurrence number sets, each cumulative occurrence number set being obtained by adding together 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 (F2k); combining together the cumulative occurrence number sets corresponding to each partial operation result to obtain combined cumulative occurrence number sets, the combination of the cumulative occurrence number sets being performed as a function of partial operations (OPk) corresponding to the partial operation results; and analyzing by the processing unit the combined 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 of an operation set of distinct cryptographic operations applied to a same data to be discovered; 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 results of at least two distinct partial operations (OPk) of the operation; selecting values in each value set for each partial operation of the operation; and for each value set and each partial operation of the operation corresponding to the value set, counting by a processing unit occurrence numbers of values transformed by a first surjective function (F1k) applied to the selected values (ECki) for the partial operation of the value set, to form an occurrence number set for the value set and for the partial operation; characterized in that it further comprises: computing by the processing unit for each partial operation result cumulative occurrence number sets, each cumulative occurrence number set being obtained by adding together 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 (F2k); combining together the cumulative occurrence number sets corresponding to each partial operation result to obtain combined cumulative occurrence number sets, the combination of the cumulative occurrence number sets being performed as a function of partial operations (OPk) corresponding to the partial operation results; and analyzing by the processing unit the combined 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. computing by the processing unit for each partial operation result cumulative occurrence number sets, each cumulative occurrence number set being obtained by adding together 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 (F2k); combining together the cumulative occurrence number sets corresponding to each partial operation result to obtain combined cumulative occurrence number sets, the combination of the cumulative occurrence number sets being performed as a function of partial operations (OPk) corresponding to the partial operation results; and analyzing by the processing unit the combined 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.