Cross‐Dimensional Steganography of Bimetal Stacked Array

Abstract Diversity and security for information transmission urgently require the rapid developments in both steganographic media and anti‐counterfeiting technology. Plasmonic holography mediated with nano‐Au or nano‐Ag has attracted much attention in enhanced data security. However, holographic systems are usually manipulated in the familiar optical dimension, which greatly increases the risk of information being deciphered. Herein, an Ag/Au bimetal stacking steganography is proposed that combines optical holography and chemical Ostwald ripening. The nano‐Au on a TaO x substrate constructs addressing‐key, which is hidden by coating a continuous Ag thin film. The confused ciphertext and computer‐generated holograms (CGH) are successively written in the stacked array by nanosecond pulsed lasers. Benefiting from the difference of the ripening reaction rate of the silver layer in halide solutions between Ag/Au/TaO x and Ag/TaO x regions, the addressing‐key information of nano‐Au can be accurately extracted, providing correct reading position coordinates for hologram display of Ag/Au/TaO x regions. This work puts a bright way to high‐security information protection.