Abstract: A method for the secure transmission of messages in real time between a transmitter and a receiver that are housed on board a motor vehicle. The method includes at least a first step that is executed during a current driving cycle of the motor vehicle and consists in the receiver comparing a received first transmitter authentication code with a first receiver authentication code. The first message being rejected if the first transmitter authentication code differs from the first receiver authentication code, and the first message being accepted if the first transmitter authentication code is identical to the first receiver authentication code.