Multi-channel Approach for Secure Metasurface-Based Image Encryption

Recent advances in two disparate but complementary research fields: <i>metasurfaces</i> and <i>hyper-spectral imaging</i>, suggest exciting new possibilities for the development of secure communication schemes. Metasurfaces can encode information in optical waves by manipulating them in the spatial and spectral domain. On the other hand, hyperspectral imagers can record optical information as a function of both position and wavelength, providing an ideal, complimentary receiver for the transmitted light. Here we introduce a novel, secure communication scheme that takes advantage of the unique opportunities provided by such spatially- and spectrally- multiplexed communication channels. While conventional image encryption approaches perform a 1-to-1 transformation on a plain image to form a cipher image, we propose a 1-to-<i>n</i> transformation scheme. Plain image data is dispersed across <i>n </i>seemingly random cipher images, each transmitted on a separate wavelength channel. The intended recipient converts the cipher images into meaningful information by using a decryption key. We show that the size of our key space grows double-exponentially with the number of channels, providing strong security against both brute force attacks and more advanced attacks based on statistical sampling of the key space. Moreover, our multi-wavelength encryption scheme can be cascaded with traditional 1-to-1 methods, effectively <i>squaring</i> the size of the key space. Our results suggest exciting new opportunities for secure transmission in multi0wavelength imaging channels.