Spatial-Spectral Physical Unclonable Functions Based on Photonic Crystal Slabs for High-Entropy Key Generation and Secure Digital Signatures

Abstract

Physical unclonable functions (PUFs) generate unique security keys from unavoidable fabrication variations. Current optical PUFs, however, often face two significant challenges: limited key capacity and the difficulty of integrating their inherently noisy physical responses with standard cryptographic protocols. Here, we introduce a high-capacity optical PUF based on photonic crystal (PhC) slabs. By coupling spatial light modulation with the rich spectral modes of the PhC slabs, we achieve an effective key length of 117,814 statistically independent bits within a compact 300 × 300 μm2 footprint. We also rigorously validate the device’s unclonability through a “True vs. Fake” hardware attack experiment. The results confirm that the extreme spectral sensitivity of the PhC PUF to stochastic nanoscale fabrication deviations makes physical cloning statistically infeasible. Furthermore, we bridge physical entropy and standard cryptographic protocols by integrating a Fuzzy Extractor with elliptic curve cryptography (ECC). This framework enables stable, secure digital signatures with a 100% verification success rate, demonstrating its potential for future hardware-based cryptography applications.