A device and a method for protecting a cryptographic module of which the method includes: estimating a functionality of a circuit that is adapted to malfunction when a physical parameter has a first value different from a nominal parameter value at which the cryptographic module functions correctly. The cryptographic module malfunctions when the physical parameter has a second value different from the nominal parameter value and a difference between the first value and the nominal parameter value being smaller than a difference between the second value and the nominal parameter value. A cryptographic module protective measure is applied if estimating that the circuit malfunctions.