For many electronic devices, such as application processors used in mobile phones or other (battery powered) equipment with wireless connections, security and data integrity have become more and more important, since such equipment is more and more used to perform sensitive operations such as payments, digital rights management, etcetera.
Tampering techniques are known to retrieve protected sensitive data, such as passwords, encryption keys, from an electronic device. For example, one of the simplest and still powerful tampering techniques is voltage tampering, when by toggling a chip supply in different ranges and different sequences, a chip can be taken out of its normal behaviour and unauthorized access to secured data be obtained.
To protect the secured data against such tampering, secured data can be stored in a special secured module, which is supplied by a dedicated, monitored, voltage supply. A protection mechanism monitors the supply and takes protective measures in case a tampering event is detected, e.g. by erasing the data in response to detecting a tampering event.
The secured module is connected to other components of the electronic device through an interface which thus allows access to the secured module. In case the electronic device is in a non-operating condition, the secured module isolates itself and the access through the interface is inhibited. However, electronic devices have to operate at increasingly lower operating voltages. Thus, the difference in voltage between the normal mode operating voltage and non-normal mode (e.g. low power mode) operating voltages becomes smaller which renders properly detecting conditions in which the secured module should be isolated more and more complex.