Metasurface-enabled optical encryption and steganography with enhanced information security.

Metasurfaces have attracted considerable interest in optical encryption due to their remarkable ability to manipulate light at subwavelength scales, however the aspect of encryption security remains an area requiring deeper exploration. Here, we propose and demonstrate metasurface-enabled optical encryption and steganography that provides dual-layer information protection. A secret information is embedded within multiple carrier images using a run-length encoding algorithm, dispersing the data to safeguard it against direct observation and brute-force attacks, thereby establishing the first layer of security. The second layer is achieved by encoding the multiple carrier images onto a silicon metasurface, leveraging light wavelength and polarization to generate diverse optical keys post-steganography. To validate the proposed scheme, several silicon metasurface samples are fabricated and characterized in the visible spectrum. By adjusting various combinations of optical keys, three encrypted carrier images are retrieved with high fidelity and negligible crosstalk, and the concealed secret information is successfully extracted through a corresponding decryption algorithm. The proposed approach enhances optical information security at the hardware level, making it less susceptible to leakage. It is anticipated that the demonstrated advancement will hold significant potential for applications in information security and optical anti-counterfeiting.