A method and apparatus for authenticating packets in a controller area network (CAN) are disclosed. The method includes transmitting messages using a mixture of message authentication codes (MACs) in a controller area network (CAN). In addition, a first MAC is generated using a first message and the first MAC is divided into a first MAC part and a second MAC part. A second MAC is generated using a second message and the second MAC is divided into a third MAC part and a fourth MAC part. A linear operation is performed between the second MAC part and the third MAC part to generate a first authentication MAC. The first message is transmitted with the first MAC part and the second message is transmitted with the first authentication MAC.