Secure Microcontroller with On-Chip Hierarchical Code Validator for Firmware Authentication

A secure microcontroller architecture has been proposed to protect the chip-level intrusion by injecting invalid firmware. The safe execution of the embedded firmware in microcontrollers is becoming important for applications requiring safety-critical operations, such as a safety-critical automotive controller, human-interactive interface. The chip-level instruction injection to bypass the original execution flow is a powerful method to acquire the privileged authority of firmware-controlled embedded systems. A code memory integrity validation accelerator for firmware authentication is proposed to provide fast hierarchical identification. The proposed validator, which is based on sector-segmented padding information, is integrated as a co-processor with the main CPU. The cyclic-redundancy code (CRC) as a fingerprint of the original code is inserted into the on-chip fab-programmed secure region to provide the sector-segmented code validation in long-range address space. The error-correcting code to identify invalid region in detail are applied to 64KB flash memory. The customized 8051-based microcontroller with the proposed accelerator is synthesized with 25,000 2-input NAND gates on 0.18um CMOS embedded-flash process.