Multi‐Level Optical Physical Unclonable Function Based on Random Surface Scattering for Hierarchical Cryptographic Protocols

Abstract Optical physical unclonable functions (PUFs) have emerged as a promising cryptographic primitive for next‐generation security. However, to harmonize with various modern networks, conventional optical PUF is inadequate due to a rigid key space with a fixed specification. This study implements hierarchically controllable randomness sources for multi‐level key generation, exploiting speckle characteristics. By adjusting illumination diameter, the speckle size can be modulated, allowing the extraction of three‐level keys with various lengths: 64, 256, and 1,024 bits. Performance evaluation reveals that all levels are superb in uniformity, uniqueness, reproducibility, and randomness. Moreover, it is proposed two feasible applications. The first is a hierarchical authentication architecture that spans from Internet of Things (IoT) devices to sensitive information, balancing security and resources. The second is a multi‐stage image encryption algorithm, exhibiting holocryptic performance superior to conventional XOR‐based encryption. This versatile platform sets a new paradigm for optical PUF, establishing a foundation for robust and expandable next‐generation security.