A test method of a circuit, 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 and each value subset, counting by a processing unit occurrence numbers (HT1, HT2) of values transformed by a respective first surjective function (F1, F2) applied to the values (EC1i[j]) of the subset of the value set, for each value set, forming n-tuples associating together one of the occurrence numbers of each of the value subsets of the value set, computing a combined occurrence number for each n-tuple of the value set by multiplying together the occurrence numbers associated by the n-tuple, and forming an occurrence number set for the value set comprising combined occurrence numbers computed 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, 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, 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 and each value subset, counting by a processing unit occurrence numbers (HT1, HT2) of values transformed by a respective first surjective function (F1, F2) applied to the values (EC1i[j]) of the subset of the value set, for each value set, forming n-tuples associating together one of the occurrence numbers of each of the value subsets of the value set, computing a combined occurrence number for each n-tuple of the value set by multiplying together the occurrence numbers associated by the n-tuple, and forming an occurrence number set for the value set comprising combined occurrence numbers computed 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, 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, 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.