Abstract Optical technologies have been widely used in information security owing to its parallel and high-speed processing capability. However, the most critical problem with current optical encryption techniques is that the cyphertext is linearly related with the plaintext, leading to the possibility that one can crack the system by solving a set of linear equations with only two cyphertext from the same encryption machine. Many efforts have been taken in the last decade to resolve the linearity issue, but none of these offers a true nonlinear solution. Inspired by the recent advance in spatial nonlinear optics, here we demonstrate a true nonlinear optical encryption technique. We show that, owing to the self-phase modulation effect of the photorefractive crystal, the proposed nonlinear optical image encryption technique is robust against the known plaintext attack based on phase retrieval. This opens up a new avenue for optical encryption in the spatial nonlinear domain.
Abstract Optical technologies have been widely used in information security owing to its parallel and high-speed processing capability. However, the most critical problem with current optical encryption techniques is that the cyphertext is linearly related with the plaintext, leading to the possibility that one can crack the system by solving a set of linear equations with only two cyphertext from the same encryption machine. Many efforts have been taken in the last decade to resolve the linearity issue, but none of these offers a true nonlinear solution. Inspired by the recent advance in spatial nonlinear optics, here we demonstrate a true nonlinear optical encryption technique. We show that, owing to the self-phase modulation effect of the photorefractive crystal, the proposed nonlinear optical image encryption technique is robust against the known plaintext attack based on phase retrieval. This opens up a new avenue for optical encryption in the spatial nonlinear domain.
We propose a novel nonlinear image-encryption scheme based on a Gerchberg-Saxton (G-S) phase-retrieval algorithm in the Fresnel transform domain. The decryption process can be performed using conventional double random phase encoding (DRPE) architecture. The encryption is realized by applying G-S phase-retrieval algorithm twice, which generates two asymmetric keys from intermediate phases. The asymmetric keys are generated in such a way that decryption is possible optically with a conventional DRPE method. Due to the asymmetric nature of the keys, the proposed encryption process is nonlinear and offers enhanced security. The cryptanalysis has been carried out, which proves the robustness of proposed scheme against known-plaintext, chosen-plaintext, and special attacks. A simple optical setup for decryption has also been suggested. Results of computer simulation support the idea of the proposed cryptosystem.
Information security has attracted much current attention due to the rapid development of modern technologies, such as computer and internet. We propose a novel method for optical image encryption using multilevel Arnold transform and rotatable-phase-mask noninterferometric imaging. An optical image encryption scheme is developed in the gyrator transform domain, and one phase-only mask (i.e., phase grating) is rotated and updated during image encryption. For the decryption, an iterative retrieval algorithm is proposed to extract high-quality plaintexts. Conventional encoding methods (such as digital holography) have been proven vulnerably to the attacks, and the proposed optical encoding scheme can effectively eliminate security deficiency and significantly enhance cryptosystem security. The proposed strategy based on the rotatable phase-only mask can provide a new alternative for data/image encryption in the noninterferometric imaging.
A novel optical image encryption system is proposed using password key based on phase retrieval algorithm (PRA). In the encryption process, a shared image is taken as a symmetric key and the plaintext is encoded into the phase-only mask based on the iterative PRA. The linear relationship between the plaintext and ciphertext is broken using the password key, which can resist the known plaintext attack. The symmetric key and the retrieved phase are imported into the input plane and Fourier plane of 4f system during the decryption, respectively, so as to obtain the plaintext on the CCD. Finally, we analyse the key space of the password key, and the results show that the proposed scheme can resist a brute force attack due to the flexibility of the password key.
In recent years, optical image encryption has attracted more and more attention in information security due to its unique advantages, such as parallel processing and multiple-parameter characteristics. In this paper, we propose a new method using three-dimensional (3D) processing strategy for interference-based optical image encryption. The plaintext is considered as a series of particles distributed in 3D space, and any one sectional extraction cannot render information about the plaintext during image decryption. In addition, the silhouette problem in the conventional interference-based optical encryption method is effectively suppressed, and the proposed optical cryptosystem can achieve higher security compared with the previous work. A numerical experiment is conducted to demonstrate the feasibility and effectiveness of the proposed method.
Abstract In this study, we propose a new nonlinear optical image encryption technique using spiral phase transform (SPT). First, the primary image is phase encoded and multiplied with a random amplitude mask (RAM), and using power function, the product is then powered to m . This powered output is Fresnel propagated with distance z 1 and then modulated with a random phase mask (RPM). The modulated image is further Fresnel propagated with distance z 2 . Similarly, a security image is also modulated with another RAM and then Fresnel propagated with distance z 3 . Next, the two modulated images after Fresnel propagations, are interfered and further Fresnel propagated with distance z 4 to get a complex image. Finally, this complex image is SPT with particular spiral phase function (SPF), to get the final encrypted image for transmission. In the proposed technique, the security keys are Fresnel propagation distances, the security image, RPM, RAMs, power order, m , and order of SPF, q . Numerical simulation results confirm the validity and effectiveness of the proposed technique. The proposed technique is robust against noise and brutal force attacks.
Abstract Optical encryption techniques in over the last 10 years have become more important in the area of optical information processing. Several applications, including online payments, medical or biometric image storage or transmission, private military applications, police identification techniques, online banking platforms, governmental services, identity (ID) cards, etc., are only a few examples. Require special and reliable security in the transmission and storage of images. Since digital picture information may be readily accessed by hackers via transmission over the Internet or other communication channels, the issue of photos with unlawful usage is becoming more and more severe. A more effective and secure means of communicating images may be offered via optical encryption. The encryption mechanism and keys are needed at the receiver side in order to decrypt the original optical data. Picture security becomes a highly important subject in communication science as a result of network growth and rising need for image transmission. There are several security issues with picture data, including forgery detection and illegal access. The most straightforward method of picture protection is to encrypt it as text. The traditional text encryption algorithms are inappropriate for picture encryption because of the high correlation present in image data. Over the last two decades, a number of optical approaches have been proposed for photo encryption, with the specific advantage of processing two-dimensional (2D) image data in parallel conduction mode. Therefore, we are doing an extensive investigation on optical image encryption in this work.