Exploiting Optical Nonlinear Temporal Coupling for Implementing Physical Unclonable Functions

In this work, we study the possibility of utilizing an LED-LDR pair for generating a Physical Unclonable Function. Towards this, the nonlinear response between an optically cou-pled LED-LDR pair, as well as the dynamic behavior of the LDR, were considered. The resulting behavior was highly nonlinear and strongly dependent on the actual physical properties of the components. We tested the idea using different LEDs (red, green, and blue; two of each color), and an LDR. Using a low-cost system (an Arduino development board), we showed that although the static response is very linear, the dynamic response is highly unpredictable, when the system is driven by random values. However, this response is identical for the same LED-LDR pairs, but different for other combinations. Additionally, the described behavior is fully repeatable. Thus, a low-cost PUF can be created using these simple components, allowing not only discrimination of the LED's color, but also for the creation of a digital fingerprint as well as authentication/verification.