Patent ID: 8880898

Claim:
A method of maintaining a version counter by a processing device, the version counter being indicative of a version of a memory content stored in said processing device, the method comprising the steps of: selectively operating the processing device in one of a first and a second mode, wherein access to operating the processing device in the first mode is limited to authorized users and controlled separately from access to the second mode; wherein operating the processing device in the first mode includes: generating at least an initial reference integrity protection value for cryptographically protecting the integrity of an initial counter value of said version counter during operation of the processing device in the second mode and wherein the initial counter value is selected from a sequence of counter values; and storing the initial reference integrity protection value as a current reference integrity protection value in a storage medium; wherein outputting reference integrity protection values of at least the current and earlier counter values of said sequence of counter values is restricted to the first mode; and wherein operating the processing device in the second mode includes: verifying the integrity of a current counter value based on the current reference integrity protection value; incrementing a current counter value to a subsequent counter value, the subsequent counter value being subsequent to the current counter value in the sequence of counter values and wherein incrementing includes removing the current reference integrity protection value for cryptographically protecting the integrity of the current counter value from said storage medium.