A cryptographic unit includes a first processing unit for determining an output signal on the basis of the AES algorithm and for determining a first comparison signal, a second processing unit for determining a second comparison signal, and a release unit for providing the output signal, wherein the release unit is designed to perform a defense measure against an external tapping of the output signal when the first comparison signal is not related to the second comparison signal in a predetermined relationship. The first comparison signal is determined in a different way as compared to the second comparison signal, so that, in the case of the injection of faults into the cryptographic unit, these faults may be detected very easily.