[0027] Embodiments of the invention modify SPI Flash memory device 110 by providing a replay protected monotonic counter storage mechanism. This is created by provisioning a common HMAC key exchanged between SPI FLash memory device 110 and platform interconnect 120 and stored, for example, in HMAC key registers 111 and 124. In this embodiment, all commands that manipulate monotonic counter 113 are authenticated commands. Since authenti cated commands can only be issued by the owner of the device key (in this embodiment, the ME execution environment 123 and the SP1 ?ash memory device 110) no other entity is able to access the monotonic counters in order to read and/or manipulate the counter.