Design and Experimental Validation of Secure Controller Area Network Messaging with the Advanced Encryption Standard

Controller Area Network (CAN) lacks native cryptography, yet many embedded control loops impose millisecond-level deadlines. We implement software-only AES-128 on commodity Cortex-M devices and quantify its real-time cost on classic CAN without changing identifiers, frame lengths, or bus occupancy. Using a purpose-built bench with one STM32F4 master and three STM32F1 slaves, protecting a 16-byte payload increases request–response latency from 540 μs to 829 μs, remaining within a 5 ms application budget. The approach preserves the physical layer, sustaining disturbances up to 15.3 V_pp, and fits within 11.2 kB flash and 1.8 kB RAM. These results provide a standards-compliant migration path to confidentiality (and replay freshness) on legacy CAN networks, establishing a compute/latency baseline that supports subsequent adoption of authenticated encryption and production key management.