Remote attestation is the process of securely verifying internal state of a remote hardware platform. It can be achieved either statically (at boot time) or dynamically, at run-time in order to establish a dynamic root of trust. The latter allows full isolation of a code region from preexisting software (including the operating system) and guarantees untampered execution of this code. Despite the untrusted state of the overall platform, a dynamic root of trust facilitates execution of critical code. Prior software-based techniques lack concrete security guarantees, while hardware-based approaches involve security co-processors that are too costly for low-end embedded devices. In this paper, we develop a new primitive (called SMART) based on hardware-software co-design. SMART is a simple, efficient and secure approach for establishing a dynamic root of trust in a re-mote embedded device. We focus on low-end micro-controller units (MCU) that lack specialized memory management or protection features. SMART requires minimal changes to existing MCUs (while providing concrete security guarantees) and assumes few restric-tions on adversarial capabilities. We demonstrate both practicality and feasibility of SMART by implementing it – via hardware modifications – on two common MCU platforms: AVR and MSP430. Results show that SMART implementations require only a few changes to memory bus access logic. We also synthesize both implementations to an 180nm ASIC process to confirm its small impact on MCU size and overall cost.

Abstract: Using mobile phones to access healthcare data is an upcoming application scenario of increasing importance in the near future. However, important aspects to consider in this context are the high security and privacy requirements for sensitive medical data. Current mobile phones using standard operating systems and software cannot offer appropriate protection for sensitive data, although the hardware platform often offers dedicated security features. Malicious software (malware) like Trojan horses on the mobile phone could gain unauthorized access to sensitive medical data. In this paper, we propose a complete security framework to protect medical data (such as electronic health records) and authentication credentials that are used to access e-health servers. Derived from a generic architecture that can be used for PCs, we introduce a security architecture specif-ically for mobile phones, based on existing hardware security extensions. We describe security building blocks, including trusted hardware features, a security kernel providing isolated applica-tion environments as well as a secure graphical user interface, and a trusted wallet (TruWallet) for secure authentication to e-health servers. Moreover, we present a prototype implementation of the trusted wallet on a current smartphone: the Nokia N900. Based on our architecture, health care professionals can safely and securely process medical data on their mobile phones without the risk of disclosing sensitive information as compared to commodity mobile operating systems. 1