Photon plays a dominant role as the information carrier in telecom, thanks to the merits of large bandwidth and low energy consumption. Optical encryption has kept attracting intensive attention in the era of frequent information exchange. Multidegrees of light facilitate enhancing the security of data transmission. Here, following the Malus law and the phase encoding rule of the geometric phase, dual-channel intensities and a far-field hologram of the transmitted light are separately programmed. Different quick response codes that link to plaintexts are recorded into two intensity channels. They are further transformed according to the predetermined rule as revealed by the hologram to form the key. The key converts the protected information in a single-pixel imaging process, and generated ciphertexts are inserted into the plaintexts to perform the encryption. The tri-channel liquid crystal device enables simultaneous encryption in two separate routes and significantly improves information security. The design supplies a universal key for data encryption.
Photon plays a dominant role as the information carrier in telecom, thanks to the merits of large bandwidth and low energy consumption. Optical encryption has kept attracting intensive attention in the era of frequent information exchange. Multidegrees of light facilitate enhancing the security of data transmission. Here, following the Malus law and the phase encoding rule of the geometric phase, dual-channel intensities and a far-field hologram of the transmitted light are separately programmed. Different quick response codes that link to plaintexts are recorded into two intensity channels. They are further transformed according to the predetermined rule as revealed by the hologram to form the key. The key converts the protected information in a single-pixel imaging process, and generated ciphertexts are inserted into the plaintexts to perform the encryption. The tri-channel liquid crystal device enables simultaneous encryption in two separate routes and significantly improves information security. The design supplies a universal key for data encryption.
The secure transmission of image information is an essential issue in communication, but it is also important in situations where the transmission channel resources are limited, such as quantum transmission. We propose a multi-layer single-pixel imaging end-to-end optical encryption framework with the characteristic advantage of a small key storage space requirement. Compared with previous single-layer encryption methods, the proposed approach greatly expands the key space and enhances the difficulty of brute-force cracking. The framework encrypts the image when the imaging signal is measured, which avoids the risk of leaking the plaintext information in processing. Numerical simulations and experiments verify the feasibility and robustness of this method. The proposed method can encrypt images end-to-end in both spatial and frequency domains, offering a new framework for robust, affordable, and secure optical image encryption.
Abstract A one-time pad encryption method combining full-phase image encryption and hiding is proposed. Firstly, original images are encoded in the phase and encrypted by phase keys loaded on the phase-only liquid crystal spatial light modulator, where the phase keys can be distributed using a quantum key distribution method. Subsequently, a host image is introduced to produce a reference wave, and overlap with an object wave to form an interferogram. Finally, based on phase-shifting interferometry, we can achieve the above encrypted image hiding. Both the simulation and experiment research demonstrate the feasibility of the proposed method, meanwhile the key and the encrypted image can be changed randomly, so the proposed system reveals the high flexibility, anti-attack ability and can be used to implement the one-time pad to achieve absolute secure transmission with the quantum key distribution method. Moreover, system security will be improved due to the fact that encryption information hidden in the host image can be treated as background noise, which does not attract the attention of the attacker.
A multiple-image encryption (MIE) scheme with a single-pixel detector has been proposed according to the principle of ghost imaging. In this scheme, each of the spatially coherent laser beams is modified by a set of phase-mask keys and illuminates on a secret image. All of the transmitted lights are recorded together by a single-pixel (bucket) detector to obtain a ciphertext, but anyone of the secret images can be decrypted from the ciphertext independently without any mutually overlapped despite some noise in them. The MIE scheme will bring convenience for data storage and transmission, especially in the case that different secret images need to be distributed to different authorized users, because the ciphertext is a real-valued function and this scheme can effectively avoid the secret images being extracted mutually. The basic principle of the MIE scheme is described theoretically and verified by computer simulations. Finally, the feasibility, robustness and encryption capacity are also tested numerically.
The hologram, which is formed by phases coupled through cascade devices for secret information sharing, still carries a cracking risk.We propose a liquid crystal planar doublet as the information carrier, and new holograms generated by the new coupled phases when the relative displacements of the different liquid crystal layers change.The designed geometrical phases are generated by an optimized iterative restoration algorithm, and each holographic image formed by these phases is readable.This scheme achieves an increase in the capacity of the stored secret information and provides more misdirection, which is expected to have potential value in optical steganography and storage.
Single-pixel imaging (SPI) enables an invisible target to be imaged onto a photosensitive surface without a lens, emerging as a promising way for indirect optical encryption. However, due to its linear and broadcast imaging principles, SPI encryption has been confined to a single-user framework for the long term. We propose a multi-image SPI encryption method and combine it with orthogonal frequency division multiplexing-assisted key management, to achieve a multiuser SPI encryption and authentication framework. Multiple images are first encrypted as a composite intensity sequence containing the plaintexts and authentication information, simultaneously generating different sets of keys for users. Then, the SPI keys for encryption and authentication are asymmetrically isolated into independent frequency carriers and encapsulated into a Malus metasurface, so as to establish an individually private and content-independent channel for each user. Users can receive different plaintexts privately and verify the authenticity, eliminating the broadcast transparency of SPI encryption. The improved linear security is also verified by simulating attacks. By the combination of direct key management and indirect image encryption, our work achieves the encryption and authentication functionality under a multiuser computational imaging framework, facilitating its application in optical communication, imaging, and security.
Abstract Recent progress in multidimensional multiplexing offers promising paths for next‐generation optical encryption. However, challenges remain in integration, dimensional expansion, and dynamic tunability. Here, a highly integrated optical encryption strategy is proposed that achieves 8‐channel multiplexing by combining polarization, wavelength, and spatial position within a single liquid crystal (LC) element, greatly increasing information capacity in a compact format. A multi‐layered nested encryption scheme is constructed, where plaintext is first encoded into a password‐protected quick response (QR) code. Decryption involves extracting far‐field holographic keys via wavelength and position, followed by Rivest–Shamir–Adleman (RSA) decryption and 26‐base preprocessing, and finally combining with polarization‐decoded data to retrieve the QR password and recover the plaintext. This hybrid scheme merges physical multiplexing with algorithmic decryption, enhancing both complexity and security. Additionally, the electro‐optical tunability of LCs adds an extra layer of security by allowing on‐demand encryption modulation. The proposed element demonstrates multifunctionality, high integration, and structural simplicity, showing strong potential for secure and scalable applications in optical encryption.