Internet-of-Things (IoT), “smart”, and Cyber-Physical Systems (CPS) devices have become increasingly popular and commonplace over the past two decades. Some of them perform safety-critical tasks and collect sensitive information, e.g., smoke detectors, temperature sensors, heart rate monitors, and fitness trackers. However, due to their stringent cost, size, and energy constraints, they are equipped with few (or no) security features. This makes them vulnerable to attacks. Some prior work proposed security architectures (such as remote attestation, proof of execution, and secure reset/erasure) to detect and mitigate malware on them. However, these approaches either partially mitigate the problem and/or require new hardware that is unrealistic for low-end devices.

This dissertation presents four hybrid (hardware/software co-design) root-of-trust (RoT) architectures that mitigate various attacks with small hardware modifications: TinyCFA, DIALED, VERSA, and CASU. TinyCFA and DIALED are passive RoTs that detect runtime (control-flow and data-only) attacks by proposing new control-flow and data-flow attestation architectures respectively. Whereas, VERSA and CASU are active RoTs that prevent sensor data privacy leakage and code-injection attacks based on hardware-enforced access control mechanisms. We implement and evaluate these architectures on low-end microcontrollers (e.g., TI MSP430) and show that they are suitable for resource-constrained IoT. We also formally verify the hardware implementation of VERSA and CASU, thus showing that they meet all stated security requirements.