Electronic control units (ECU) have been widely used in modern resource-constrained automotive systems, communicating through the controller area network (CAN) bus. However, they are still facing man-in-the-middle attacks in CAN bus due to the absence of more effective authentication/encryption mechanism. In this paper, to more effectively defend against the attacks, we propose an unified lightweight authenticated encryption that integrates recent prevalent cryptography standardization ISAP and ASCON. Experimental results show that our proposed unified lightweight authenticated encryption can reduces 26.09%area consumption on Xilinx Artix-7 FPGA board compared with the state-of-the-arts. In addition, the encryption overhead of the proposed design for transferring one CAN data frame is 10.75 us using ASCON and 72.25 us using ISAP at the frequency of 4 MHz on embedded devices.