Internet of Things (IoT) devices can be considered a significant component within cyber-physical systems. They can provide network communication in addition to controlling the various sensors and actuators that exist within the larger cyber-physical system. IoT devices tend to be small and contain a limited battery supply. They typically have strict constraints placed on their power consumption and available hardware resources. It is for these reasons that energy-efficiency is a major consideration in the design of these resource-constrained devices. In addition, these devices are often deployed in unsecured locations which raises concerns about the security of the device. However, the limited amount of available resources presents an obstacle towards the implementation of security protocols for these cyber-physical systems. Physically Unclonable Functions (PUFs) show promise as a potential security option. PUFs can help provide protection from issues such as IC piracy, counterfeiting, etc. Furthermore, solar cells have been utilized as a power source in IoT devices. In this paper, we propose a novel solar cell-based PUF that leverages the intrinsic variations present in solar cells. As a proof of concept, we have constructed multiple copies our proposed solar cell-based PUF using amorphous silicon, monocrystalline silicon, and polycrystalline solar cells. The reliability and uniformity of the responses produced by the copies of the PUFs made from the different types of solar cells were evaluated against variations in temperature and light intensity. From our experiments, we found that with respect to temperature the range of average reliability values was 84.41–91.20% and the range of average uniformity values was 49.34–51.26%. With respect to light intensity, the range of average reliability values was 95.45–97.75% and the range of average uniformity values was 48.74–52.81%. In addition, Monte Carlo simulations performed on monocrystalline silicon resulted in a uniqueness value of 49.989%.
