Flexible and Wearable Encryption Primitive Based on Optical Physically Unclonable Functions

According to explosive and rapid development of flexible circuit technology, massive demand for wearable devices has arisen. Furthermore, wearable devices with integrated smartphones have contributed to a potential influence on online banking, digital healthcare service, and digital personal identification. This all-in-one device enables user to experience enhanced convenience; however, it also entails the inherent risk of cyber infiltration. A single successful hack into the device could endanger the security of user. Therefore, it is imperative to implement robust encryption and authentication mechanisms within wearable devices. Herein, we suggest a flexible and wearable encryption primitive based on an optical physically unclonable function which has a high capability of being embedded into a wearable device. Stochastic and unpredictable process-driven security concept, physically unclonable function (PUF) can operate as a solid identifier against online and offline intrusion. The physically unclonable tag consists of screen-printed Ag on the polyimide. The micro-scaled morphological characteristics of Ag-paste tag (APT) diverge as the fabrication step is repeated. In terms of PUF appliance potential (i.e., uniformity, reproducibility, uniqueness, and randomness) and real-case demonstration results (i.e., sensor-attached and smartphone-integrated operation) manifest that the APT functions as a strong encryption system embedded in a wearable device.