PISTIS: Trusted Computing Architecture for Low-end Embedded Systems

Recently, several hardware-assisted security architectures have been proposed to mitigate the ever-growing cyberattacks on Internet-connected devices. However, such proposals are not compatible with a large portion of the already deployed resource-constrained embedded devices due to hardware limitations. To fill this gap, we propose PISTIS, a puresoftware trusted computing architecture for bare-metal lowend embedded devices. PISTIS enables several security services, such as memory isolation, remote attestation and secure code update, while fully supporting critical features such as Direct Memory Access (DMA) and interrupts. PISTIS targets a wide range of embedded devices including those that lack any hardware protection mechanisms, while only requiring a few kilobytes of Flash memory to store its root of trust (RoT) software. The entire architecture of PISTIS is built from the ground up by leveraging memory protectionenabling techniques such as assembly-level code verification and selective software virtualisation. Most importantly, PISTIS achieves strong security guarantees supported by a formally verified design. We implement and evaluate PISTIS on MSP430 architecture, showing a reasonable overhead in terms of runtime, memory footprint, and power consumption. Table 1: PISTIS vs. State-of-the-art trusted computing architectures from various perspectives.