RETENTION AND REVOCATION OF OPERATION KEYS BY A CONTROL UNIT

An electronic key fob device, in one embodiment, includes a transmitter, a counter configured to provide a current counter value indicated by a plurality of bits, a memory configured to store an operation key, and a processor coupled to the transmitter and memory. The processor is configured to encrypt the current counter value using the operation key to produce an encrypted counter value, select a subset of the plurality of bits of the current counter value, transmit a message the includes the encrypted counter value and the subset of plurality of bits of the current counter value.