Magnetically encoded plasmonics for physical information encryption

Physical security tags are increasingly vulnerable to replication as computational capabilities continue to advance. Here, we present a magnetoplasmonic keychain that encodes three-dimensional magnetic field configurations into polarization-dependent optical states through the controlled alignment of anisotropic plasmonic nanostructures. Unlike conventional physically unclonable functions, this platform enables deterministic information encoding while preserving a fundamentally non-invertible decoding process. By spatially multiplexing three independent magnetic field configurations within a 60-pixel architecture, the system achieves a physical encoding space on the order of 10⁴⁴. Without knowledge of the magnetic field configurations and their spatial arrangement, recovery of the encoded information becomes fundamentally infeasible because multiple physical configurations produce identical optical observations, causing supervised learning models to perform no better than random guessing. In contrast, complete knowledge of the encoding configuration enables rapid and accurate information recovery through simple polarization-resolved optical imaging. These results establish a physically enforced one-way encryption strategy that complements conventional computational cryptography and provides a scalable platform for secure authentication and high-density physical information storage.