Security against replay of a message by generating a list of unique message enabling codes (TATs) in a first device and storing the list in a second device. A message generated in the first device, which includes at least one of the unique message enabling codes from the list, is transmitted to the second device. The unique message enabling code of the received message is compared with the list stored in the second device to determine whether or not to enable processing of the message by the second device. If the unique message enabling code received with the message is included in the stored list, processing of the message is enabled and, the corresponding unique message enabling code is deleted from the stored list. If the unique message enabling code received with the message is not included in the stored list, processing of the message is rejected.