A system and method of verifying data at a microcontroller using message authentication codes (MACs) includes generating at a microprocessor of the microcontroller a valid MAC using valid data; transmitting the valid MAC to a peripheral of the microcontroller along with the valid data; receiving an authentication message at the microprocessor from the peripheral in response to transmitting the valid MAC; generating at the microprocessor an invalid MAC, which is created by changing one or more bits of the valid MAC; transmitting the invalid MAC to the peripheral along with the valid data in response to the authentication message; and receiving a second authentication message at the microprocessor from the peripheral in response to transmitting the invalid MAC.