Compressive Imaging Encryption with Secret Sharing Metasurfaces

Abstract

imaging modalities, computational ghost imaging (CGI) and visual cryptography (VC), [5,6] have demonstrated their great potential in optical encryption. [7][8][9][10][11][12] In CGI, a sequence of computer-generated mask patterns are projected onto the target object, and a single-pixel detector is employed to record the relevant intensity values reflected or transmitted from the object. A decryption-like computational process is then applied to reconstruct the object image from the mask patterns (i.e., keys) and intensity values (i.e., ciphertext). Various optical encryption schemes based on CGI have been proposed for multipositioned or multicolored image encryption. [13,14] Different from the computational reconstruction of CGI, VC enables a direct observation of the secret image by naked eyes. In VC, a secret image is split into multiple shared key images. The predesigned shared images with incoherent overlays can decode the secret image visually by gathering their independent subinformation. By combining holography and VC, optical encryption schemes have been developed by hiding the secret image into different pieces of phase keys. [15][16][17][18] Meanwhile, rapid progress has been made in optical encryption, thanks to the development of metasurfaces. [19][20][21][22][23][24][25][26] Metasurfaces, consisting of single-layer or fewer-layer spatially variant meta-units, enable unprecedented control over the phase profile and other degrees of freedom of light with subwavelength resolution. [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] With polarization or wavelength control, optical Exploiting various degrees of freedom of light, metasurfaces have unique advantages in multiple-channel information storage and demonstration, which thereby provides a novel platform to convey the keys and cipher images for different encryptions. Following the secret sharing principle of visual cryptography (VC), the authors here successfully embed both the keys and cipher images of computational ghost imaging (CGI) encryption into the holographic metasurface-images (meta-images). The decryption process starts with key retrieval via optical observation of overlapped meta-images, followed by a compressive CGI calculation to reconstruct the target images according to the obtained key and steganographic cipher images with a high compression ratio of 4. By integrating metasurface imaging, VC, and CGI, the authors' proposed encryption scheme exempts conventional key distribution and transmission of CGI, enhances the security by secret sharing of VC, and increases the amount of hiding data contained in meta-images with compressive sensing.

Enriching Metasurface Functionalities by Fully Employing the Inter‐Meta‐Atom Degrees of Freedom for Double‐Key‐Secured Encryption

“…To further improve the information encryption performance of metasurfaces, Zheng et al proposed the novel concept of combining the metasurfaces with optical encryption, which can greatly increase the storage capacity and security of metasurface information devices. [44,47] Therefore, it is believed that if the idea of fully using the DoFs of metasurfaces can be integrated with the computational imaging schemes, security and data storage capacity can be improved for the optical encryption.…”

Meta-optics empowered vector visual cryptography for high security and rapid decryption

“…A pioneering work that combines metasurface with ghost imaging or single-pixel imaging provides a framework to solve the integration problem and enhance the security level 55 . In recent investigations, the security level has been improved by integrating metasurface imaging, visual cryptography, and computational imaging 56 , 57 . Generally, owing to the indirect imaging manner of computational imaging, multiple optical measurements or additional digital post-processing are required for hidden image restoration.…”

Multiplexing Optical Images for Steganography by Single Metasurfaces

“…[27,28] In recent years, researchers have devoted more attention to multifunctional applications and integrated meta-devices. [29][30][31][32] Therefore, multifunctional metasurface may be introduced to the emerging field of optical image steganography, rather than the familiar digital-image steganography, which will address the issue of single-channel steganography, [33,34] so that a sender can transfer independent information to multiple receivers. In this multiplexing optical image steganography case, some secret information can be embedded into a media and extracted by multiple receivers with specialized keys.…”