Dynamic Cryptography through Plasmon‐Enhanced Fluorescence Blinking.

Merging cryptographic primitive technologies and physical unclonable functions (PUFs) have become a new paradigm of one‐way encryption. Herein, the authors report a dynamic PUF cryptographic primitive based on plasmonic fluorescence blinking from single or a few dye molecules embedded within the nanogaps of plasmonic patch nanoantennas. This cryptographic primitive carries two sets of high‐capacity optical codes: the fluorescence blinking of the embedded dye molecules and multi‐color light scattering enabled by the plasmonic nanoantennas. The former allows the generation of temporal binary codes from a large number of individual plasmonic patch nanoantennas by holding either "1" (bright state) or "0" (dark state), while the latter provides a permanent color‐based novenary code that acts as a decryption channel for authentication. Benefiting from the high electromagnetic field localized within the nanogaps and the large Purcell enhancement of the plasmonic nanoantennas, the fluorescence blinking is readily detectable by a common fluorescence microscope with a mercury arc lamp as a low‐power excitation source. The developed dynamic PUF codes are robustly and accurately authenticated by a self‐programmed computer vision algorithm. This study revolutionizes the conventional static PUF encryption to nanophotonics‐based dynamic encryption, opening a new avenue for next‐generation advanced anti‐counterfeiting. [ABSTRACT FROM AUTHOR]