RealSWATT: Remote Software-based Attestation for Embedded Devices under Realtime Constraints

Abstract

Smart factories, critical infrastructures, and medical devices largely rely on embedded systems that need to satisfy realtime constraints to complete crucial tasks. Recent studies and reports have revealed that many of these devices suffer from crucial vulnerabilities that can be exploited with fatal consequences. Despite the security and safety-critical role of these devices, they often do not feature state-of-the-art security mechanisms. Moreover, since realtime systems have strict timing requirements, integrating new security mechanisms is not a viable option as they often influence the device's runtime behavior. One solution is to offload security enhancements to a remote instance, the so-called remote attestation. We present RealSWATT, the first software-based remote attestation system for realtime embedded devices. Remote attestation is a powerful security service that allows a party to verify the correct functionality of an untrusted remote device. In contrast to previous remote attestation approaches for realtime systems, RealSWATT does neither require custom hardware extensions nor trusted computing components. It is designed to work within real-world IoT networks, connected through Wi-Fi. RealSWATT leverages a dedicated processor core for remote attestation and provides the required timing guarantees without hardware extensions. We implement RealSWATT on the popular ESP32 microcontroller, and we evaluate it on a real-world medical device with realtime constraints. To demonstrate its applicability, we furthermore integrate RealSWATT into a framework for off-the-shelf IoT devices and apply it to a smart plug, a smoke detector, and a smart light bulb.