Matched Digital PUFs for Low Power Security in Implantable Medical Devices

Wireless communication is widely used in Implantable Medical Devices (IMDs) to facilitate data transmission, device programming, and real time monitoring. However, wireless systems are easy targets for attackers to inspect and potentially breach. Thus, security and privacy have become principal design requirements for IMDs. The challenge in secure IMD design stems from the conflicting constraints of the IMD (e.g. Utility, safety, privacy, security, size, and low power). In this paper, we propose a new ultra low power approach for non-invasive and secure communication and operation of IMDs. We exploit the inherent process variations in an FPGA's SRAM cells to create a unique and random input-output mapping, which we then match in an ASIC design, thus, creating two matched digital physical unclonable functions (PUFs). The smaller design is embedded with the IMD while the FPGA remains with the programmer (e.g. Doctor). We present our architecture, introduce accompanying protocols for secure cryptographic communication and trusted remote computation, and provide an analysis of the system's resilience to various security attacks. Our system is the first hardware-based digital security system proposed for IMDs. It is orders of magnitude lower in delay and energy consumption that traditional cryptographic techniques.