Conventional Double Random Phase Encoding Research Articles

Optical color image encryption scheme with a novel DNA encoding algorithm based on a chaotic circuit

An optical setup with a unique color image cryptography technique employing a chaotic system is suggested in this study. For this purpose, deoxyribonucleic acid (DNA) encoding is used as an encryption method. Rössler attractor is employed as a chaotic system and it consists of three differential equations. In order to implement the chaotic system by analog electronic components, a circuit design including operational transconductance amplifier (OTA) is also suggested. Circuit simulations have been performed utilizing LT spice program. In the proposed study, the number of DNA encoding rules has excessively been increased compared to previous studies on DNA encoding technique. Thus, the security of the encryption scheme is enhanced. Numerous security tests such as correlation coefficient, histogram, Shannon entropy, secret key and initial condition sensitivities, plaintext and ciphertext attacks and differential attack have been carried out to evaluate functioning of the introduced cryptography algorithm. The numerical test results prove that the suggested encryption algorithm can resist statistical and differential attacks. Moreover, the cryptology scheme indicates the behavior of sensitivity to initial condition and secret key. The presented algorithm has great performance from the point of encoding rules number and being robust against differential attack. Moreover, enhanced double random phase encoding (DRPE) technique is used in optical stage of the study. By modifying the conventional DRPE method, correlation value between R, G, B components for same pixel have extremely reduced. All numerical analyses regarding chaotic system and encryption scheme have been performed in MATLAB program.

Security-enhanced optical nonlinear cryptosystem based on double random phase encoding

Security is the critical requirement for optical encryption. A security-enhanced nonlinear cryptosystem is designed by introducing a time-varying nonlinear term in the double random phase encoding (DRPE) system. The nonlinear term, which is a randomly generated complex distribution, is introduced in the encryption process and has no influence on the decryption of original image. The nonlinear term is not transmitted to receivers of ciphertexts, therefore, there is no need to manage and distribute it. The designed cryptosystem is demonstrated to be resistant to various attacks including ciphertext-only attacks, known-plaintext attacks and chosen-plaintext attacks. In addition, the nonlinear cryptosystem is simple, and has the same optical implementation as that of conventional DRPE system.

Security enhancement of double random phase encryption with a hidden key against ciphertext only attack

In this paper, we propose a security enhanced double random phase encoding (DRPE) encryption system against common ciphertext only attacks (COA). We point out one common weakness of COA schemes that the cracked plaintext image is usually in wrong circularly shifting positions and flipping status. Regarding to this weakness, an extra security layer (either optical or digital) cascaded with the DRPE system is constructed using a hidden key in our work. Simulation results demonstrate that our proposed system has significantly better security strength against COA than conventional DRPE system.

Optical triple random-phase encryption

We propose an optical security technique for image encryption using triple random-phase encoding (TRPE). In the encryption process, the original image is first double-random-phase encrypted. The obtained function is then multiplied by a third random-phase key in the output plane, to enhance the security level of the encryption process. This method reduces the vulnerability to certain attacks observed when using the conventional double random-phase encoding (DRPE). To provide the security enhancement of the proposed TRPE method, three attack cases are discussed: chosen-plaintext attacks, known-plaintext attacks, and chosen-ciphertext attacks. Numerical results are presented to demonstrate feasibility and effectiveness of the proposed method. Compared with conventional DRPE, the proposed encryption method can provide an effective alternative and has enhanced security features against the aforementioned attacks.

Optical image encryption using Kronecker product and hybrid phase masks

In this paper, we propose a new technique for security enhancement in optical image encryption system. In this technique we have used the Kronecker product of two random matrices along with the double random phase encoding (DRPE) scheme in the Fresnel domain for optical image encryption. The phase masks used here are different than the random masks used in conventional DRPE scheme. These hybrid phase masks are generated by using the combination of random phase masks and a secondary image. For encryption, the input image is first randomized and then the DRPE in the Fresnel domain is performed using the hybrid phase masks. Secondly, the Kronecker product of two random matrices is multiplied with the DRPE output to get the final encoded image for transmission. The proposed technique consists of more unknown keys for enhanced security and robust against various attacks. The simulation results along with effects under various attacks are presented in support of the proposed technique.

Optical encryption with protection against Dirac delta and plain signal attacks.

This Letter proposes an optical encryption technique that disguises the information with modular arithmetic concepts and time-varying noise components that are unknown to the receiver. Optical encryption systems that use these techniques produce a nondeterministic system response, as well as noise like image data that can easily be generated with ordinary spatial light modulators. The principle of this technique is demonstrated for the double random phase encoding (DRPE) method. The conventional DRPE method has major vulnerabilities for Dirac signal and plain signal attacks, making them impractical for secure encryption. It is shown that the proposed encryption technique provides a robustness against these types of attacks, allowing optical DRPE to be employed in secure encryptions. Moreover, applications of this Letter are not limited to DRPE alone but can also be adopted by other optical encryption techniques such as fractional Fourier transform and Fresnel-transform-based techniques.

An optical encryption and authentication scheme using asymmetric keys.

We propose a novel optical information encryption and authentication scheme that uses asymmetric keys generated by the phase-truncation approach and the phase-retrieval algorithm. Multiple images bonded with random phase masks are Fourier transformed, and obtained spectra are amplitude- and phase-truncated. The phase-truncated spectra are encoded into a single random intensity image using the phase-retrieval algorithm. Unlike most of the authentication schemes, in this study, only one encrypted reference image is required for verification of multiple secured images. The conventional double random phase encoding and correlation techniques are employed for authentication verification. Computer simulation results and theoretical explanation prove the effectiveness of the proposed scheme.

Encrypted imaging based on algebraic implementation of double random phase encoding.

The security of important information captured by sensors and cameras is currently a growing concern as information theft via techniques such as side-channel attacks become increasingly more prevalent. Double random phase encoding (DRPE) is an optical encryption method based on optical Fourier transform that is currently being used to implement secure coherent optical systems. In this paper, we propose a new DRPE implementation for incoherent optical systems based on integral photography that can be applied to "encrypted imaging (EI)" to optically encrypt an image before it is captured by an image sensor. Because the proposed incoherent DRPE is constituted from conventional DRPE by rewriting the optical encryption via discretization and Euler's formula, its security level is the same as that of conventional DRPE. The results of an experiment in which we encrypted a plaintext image optically and then decrypted it numerically demonstrate that our proposed incoherent optical security system is feasible.

Fresnel domain nonlinear optical image encryption scheme based on Gerchberg–Saxton phase-retrieval algorithm

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.

Security enhanced optical encryption system by random phase key and permutation key

Conventional double random phase encoding (DRPE) encrypts plaintext to white noise-like ciphertext which may attract attention of eavesdroppers, and recent research reported that DRPE is vulnerable to various attacks. Here we propose a security enhanced optical encryption system that can hide the existence of secret information by watermarking. The plaintext is encrypted using iterative fractional Fourier transform with random phase key, and ciphertext is randomly permuted with permutation key before watermarking. Cryptanalysis shows that linearity of the security system has been broken and the permutation key prevent the attacker from accessing the ciphertext in various attacks. A series of simulations have shown the effectiveness of this system and the security strength is enhanced for invisibility, nonlinearity and resistance against attacks.

Security enhancement of double-random phase encryption by amplitude modulation

Conventional double-random phase encoding is vulnerable to a chosen or known plaintext attack owing to the linearity of the system. We introduce a technique to break down this linearity with an undercover amplitude modulation in the encryption scheme. As an additional key, this operation can significantly enhance the security of the system. A series of computer simulations have shown the effectiveness of this method and its resistance against the known plaintext attack. The design and parameter choice of the amplitude modulator is also discussed.