A method of transmitting data within a vehicle includes: storing two copies of a data message; constructing at an electronic control unit (ECU) a serial bus message that includes one copy of the data message and a message authentication code (MAC) created using a secret key stored at the ECU, a MAC algorithm, and a different copy of the data message; transmitting the serial bus message to a receiving ECU over a vehicle bus; authenticating the serial bus message at the receiving ECU using a copy of the key stored at the receiving ECU by creating a copy of the MAC from the data message included in the serial bus message and the copy of the key; comparing the MAC from the serial bus message with the copy of the MAC created at the receiving ECU; and rejecting or accepting the data message based on the comparison.