2.2.1.7.1 The Authenticated Command Message

ProtocolVersion (1 byte): Contains the protocol version. The protocol version is 0x03.

MessageType (1 byte): Contains the authenticated command message type. The authenticated command message type is 0x0c.

SessionID (16 bytes): Contains the 128-bit session ID. This value is sent by the transmitter in the Registration Response message.

Counter (4 bytes): Contains a counter for Authenticated Commands. For each Authenticated Command between the receiver and the transmitter, both the Receiver and transmitter independently increment the counter. The counter MUST be in sync for the transmitter to carry out the Authenticated Command. This mitigates a replay attack.

CommandType (4 bytes): Indicates the type of authenticated command.

CommandLength (4 bytes): Contains the length, in bytes, of the authenticated command.

CommandParameters (variable): Contains command parameters as dictated by Id and length.

OMAC (16 bytes): Contains the 128-bit AES-OMAC1 [OMAC] signature. The signature is generated over the concatenation of the Counter field ORed with the Command Data field, including Id and length.