I’m a little confused about the write operation of the NXP A1006 when it is in “Authentication Operation” mode.
In “sd276413 - Objective short data sheet A1006, Secure Authentication IC (1.3).pdf” section 9.3.1 it is states that “Depending on the IC life cycle status the memory write operation is restricted to some specific memory areas and arbitrary data write operations are not possible but only non-reversible write operations are possible.”
Both “sd276413 - Objective short data sheet A1006, Secure Authentication IC (1.3).pdf” and “ds374620 - A1006 Secure Authenticator IC (2.0).pdf” state that in “Authentication Operation” “Only write operations to the user memory possible, for example transactional “usage data” updates” are possible but there is no exact definition of “transactional “usage data” updates”.
The problem is that “ds374620 - A1006 Secure Authenticator IC (2.0).pdf” states in Fig 16 that during “Authentication Operation” “Write arbitrary data to User Memory and read operation allowed”.
The A1006 does not have a counter like the Infineon SLE95250 or the NXP A1007.
I had planned to implement a counter using 1 bit per count in “Authentication Operation" mode because I thought that “only non-reversible write operations are possible” in this mode.
But if one can “Write arbitrary data to User Memory ” in “Authentication Operation" mode, then I cannot make a tamper-proof counter in the A1006.
Can anyone clarify the write permissions for the A1006 in "Authentication Operation" mode?
