Complex Media Multiple Optical Encryption System with Spatiotemporal‐Projection‐Based Key Space Expansion

ABSTRACT Scattering of light in complex media enables physics‐assisted encryption, introducing multi‐dimensional complexity and physical unclonability to the system. Current encryption approaches based on complex media suffer from limited key spaces constrained to the space domain. This manuscript proposes a complex media multiple encryption system with spatiotemporal‐projection‐based key space expansion. Three independent parameters extracted in the projection process govern the expanded key spaces. The reliable reconstruction of decryption keys (trained deep neural networks) and the effective expansion of the key space are experimentally validated. The system shows favorable resistance to both cross‐attacking and overlapping threats according to the parameter tolerance. In a transmission task for the scene image, the system demonstrates a bit error rate as low as 3.815 × 10 −5 for the transmission, while approaching the value of random guessing (0.5) for the encryption. This manuscript establishes a novel framework for complex media multiple optical encryption systems, with effective key space expansion, simplified configurations, and remarkable performance in image transmission and encryption.