METHOD FOR MAKING SECURE A LOGICAL OR MATHEMATICAL OPERATOR IN A MICROPROCESSOR-BASED ELECTRONIC MODULE

摘要

The invention concerns a method for making secure a logical or mathematical operator, in the present case the XOR operator, usable in executing a programme in a microprocessor-based electronic module. The invention is characterised in that the execution of the XOR operator is replaced by the execution (CAL-XORSEC (i)) of a sequence (Si) of operations having as final result a result identical to the result of the XOR function. The sequence of operations (Si), in the present case, consisting of elementary operations based on AND, OR, and NOT, is selected from a set of eight equivalent sequences (S1 to S8) after determining (CAL-NDO) a serial number NDO = i based on parameters of the programme and/or a random parameter R supplied by a pseudo-random number generator (24).