An apparatus and method are utilized for transmitting data across an interface between a sender and a receiver. The sender and receiver can be provided with a shared key, a receiver_—key and a sender_—key. A payload message can be combined with the keys to generate a unique message for transmission across the interface. The payload message can be authenticated utilizing the same input and the same algorithm on the receiving end of the transmission. The resulting confirmatory payload message can be utilized with the authenticating payload message to authenticate the payload message.