A secure protocol consisting of two different security-level message authentications over CAN

In the presented paper, we will propose a secure protocol against tampering and replay attacks for the data frame over Controller Area Network (CAN). Our proposal consists of two authentication methods preventing tampering attacks. The first method is to generate a message authentication code (MAC) for each message in CAN data frame. This method uses the truncated MAC in order to send the message and a part of MAC in one data frame. The second one is to calculate a MAC for some messages. In this method, some data frames are transmitted in order to send full of the MAC. The first method can be performed with high frequency, although it has low security because of a truncation of the MAC. In the other hand, the second method is high security, although it can be performed with low frequency. For replay attacks, our proposal uses transaction numbers and the common key, which a sender and a receiver shared in advance.