In a general aspect, a test method can include acquiring a plurality of value sets, each including values of a physical quantity or of logic signals, linked to the activity of a circuit to be tested when executing distinct cryptographic operations applied to a same secret data, for each value set, counting occurrence numbers of the values of the set, for each operation and each of the possible values of a part of the secret data, computing a partial result of operation, computing sums of occurrence numbers, each sum being obtained by adding the occurrence numbers corresponding to the operations which when applied to a same possible value of the part of the secret data, provide a partial operation result having a same value, and analyzing the sums of occurrence numbers to determine the part of the secret data.