Multi-key optical encryption based on two-channel incoherent scattering imaging.

With the rapid development of computer network technology, information security has attracted increasing attention. Due to the characteristics of multi-dimensional operation and parallel processing capability, optical image encryption techniques have been receiving more and more attention. Since the well-known double random phase encoding technique was proposed, many other methods based on optical information processing means such as the use of optical transform, interference, and polarized light encoding, have been proposed for optical image encryption. However, recent researches have demonstrated that traditional optical encryption techniques are symmetric cryptosystems, in which decryption keys are identical to encryption keys and they have been found to be vulnerable to different types of attacks, such as known plaintext and chosen plaintext attacks. To overcome this shortcoming, asymmetric cryptosystems based on nonlinear phase-truncation techniques and phase retrieval algorithm have been proposed. Asymmetric cryptosystem is a cryptographic system in which encryption keys are different from decryption keys. The encryption keys are used as public keys which are disseminated widely, and the decryption keys are used as private keys which are known only to the authorized users. So, asymmetric cryptosystem can offer a higher-level security than symmetric cryptosystem. However, asymmetric cryptosystems based on phase retrieval algorithms require a lot of computational time, and asymmetric cryptosystems based on phase-truncated Fourier transforms have been found to be vulnerable to special attack. Therefore, in this paper, a novel asymmetric image encryption method is proposed by using the gyrator transform and vector operation. The original image is encrypted into two phase masks with vector operation. One is a random phase mask and the other is a phase mask related to the original image. In the encryption process, the random phase mask is used as a phase key and the other phase mask is transformed by gyrator transform. The transform result is performed by Fourier transform after being modulated by a phase distribution. The ciphertext is the amplitude of the above result. Compared with previous encryption schemes, the suggested method has two advantages. Firstly, we have proposed a new asymmetric encryption method based on the gyrator transform and vector operation. The decryption process is different from the encryption process. The gyrator transform and Fourier transform are used in the encryption process, while only the inverse operation of Fourier transform is employed in the decryption process. In addition, the decryption keys produced in the encryption process are different from the encryption keys. Therefore, the proposed scheme has high resistance against the conventional attacks. Secondly, the encrypted result is real-valued, which is convenient for display, transmission and storage.Numerical simulations illustrate the feasibility and effectiveness of the proposed encryption scheme.

The RC-5 algorithm is an algorithm with the encryption method using the symmetric method and processing in the form of a cipher block, the same keywords are used for the encryption and decryption processes. The testing and analysis phase consists of a). Testing the execution time of the key generation process (set up key) b). Testing the success of the encryption and decryption process on the client-server integration method c). Testing the success of the encryption and decryption process using the file operation method d). Comparison of overhead/file size before and after passing through the system. The testing phase and execution time analysis are carried out when using the file operation method where the test will be divided into 3 parts, namely the execution time for the key setup process, the encryption process, and the decryption process. Testing the success of the encryption and decryption process on the client-server integration method is divided into 2 parts, namely testing the encryption process and the decryption process. In testing the encryption process, the characters that will be sent to the server will be encrypted first with a key to becoming a ciphertext in the form of integer data. The test results obtained are 1). The execution time for key generation (set up key) is very fast, around 9-10 ns. 2). In the encryption and decryption process, the execution time depends on the size of the plaintext file. The larger the plaintext file size, the longer the execution time. Where for a file with a size of 1 kb requires an execution time of 50.6 ms in the encryption process. 3). There is no difference between the size of the file before entering encryption and after decryption. Where for files with a size of 500 bytes before entering the encryption process, a file of 500 bytes will be generated from the decryption process.

We present a novel method for optical image encryption based on a modified radial shearing interferometer (MRSI), which is generally used for wavefront reconstruction. In this method, a plaintext image is first encoded into a phase-only mask (POM) and then modulated by a random phase mask (RPM), the result is regarded as the input of the radial shearing interferometer and is divided into two coherent lights, which interfere with each other, leading to an interferogram (ciphertext). The aforementioned encryption process can be achieved digitally or optically while the decryption process can only be analytically accomplished. Numerical simulation is provided to demonstrate the validity of this method.

This paper offers a security analysis of an optical image cryptosystem that integrates interference and unequal modulus decomposition (EMD). In contrast to the conventional interference-based cryptosystem, which utilizes a single phase-only mask (POM) derived from the encryption process as the private key, the enhanced cryptosystem employs two random phase masks (RPMs) and two POMs derived from the phase-reserved (PR) structure as private keys. This modification addresses the silhouette problem inherent in the conventional interference-based cryptosystem by expanding the key space, thereby enhancing security strength. However, it is determined that the RPM R2(u,v) and the POM P2(x,y) exhibited low key sensitivity, thereby limiting their impact on the security enhancement. Additionally, due to the independence from the plaintext, the RPMs employed as private keys can be recovered using a designed known-plaintext attack (KPA). Once the RPMs are recovered, the number of unknown keys is reduced to two. This enables the recovery of plaintext information from its ciphertexts via a subsequent ciphertext-only attack (COA) without any prior knowledge of the POMs. In light of these findings, a novel hybrid attack strategy, to our knowledge, is proposed, integrating four cascaded KPAs and a COA, to effectively compromise the advanced interference and EMD-based cryptosystem. To validate the feasibility and effectiveness of the proposed hybrid attack, numerical simulations have been conducted.

In this paper, fault detection scheme is introduced to improve the security and reliability of the NTRU in realistic environments, such as operating over a network. As the NTRU will be working in real networks, which have their own set of transient errors, handling such errors in analyzing the NTRU becomes a must. A single transient error occurring during the NTRU encryption (or decryption) process will likely result in a large number of errors in the encrypted/decrypted data. Such faults must be detected before sending data to avoid the transmission and use of erroneous data. Concurrent fault detection is important not only to protect the encryption/decryption process from random faults, but it will also protect the decryption circuitry from an attacker who may maliciously inject faults in order to find the secret key. We first describe the effects that faults may have on NTRU security while operating over a network by analyzing the propagation of such faults to the outputs. We then present two fault detection schemes: The first is a redundancy-based scheme while the second uses an error detection code. The latter present fault detection schemes by using an error detecting code, using one parity bit. We will add the parity bits to the polynomials and disable the device output when any of these parity checks are violated. This fault detection scheme has more than 99% coverage fault detection in the encryption process and in the first part in the decryption process. In the second part in the decryptionprocess, it has more than 67 % coverage fault detection. We can increase this ratio to high fault detection by adjusting the choices of the parameters of the NTRU network security system.

Iterative partial phase encoding based on joint fractional Fourier transform correlator adopting phase-shifting digital holography

An encryption system that combines compressive sensing (CS) and two‐step parallel phase shifting digital holography (PPSDH) using double random phase encoding (DRPE) is presented in this paper. The two‐step PPSDH is a linear inline holographic scheme and is much suitable for encrypting the 2D/3D information in a single exposure. The distribution of random phase mask (RPM) in the DRPE is implemented using circular harmonic key which increases the security of the encryption process. In this system, the keys used to encrypt are spatial positions of the planes, wavelength, and rotation of the circular harmonics in RPMs, and CS acts as an additional key that makes the system more secure than the conventional optical encryption methods. At the transmission end, two‐step PPSDH is applied to encrypt the object information in single hologram. The digital mirror device (DMD) is placed between the object and a single‐pixel detector for acquiring fewer hologram measurements. At the receiver end, the single digital hologram is numerically recovered by using a CS optimization problem. The original complex object field is decrypted from the CS recovered holograms by the inversion of two‐step PPSDH process with the help of the correct keys. The numerical simulations are presented for complex 2D and 3D objects to test the feasibility of the proposed encryption and decryption system. The proposed method carried out intensity and phase reconstruction of the original object field using single‐pixel compressive imaging. The computer simulation results demonstrated that the encrypted information is highly secured with the rotation of the circular harmonic key. The sensitivity of the decrypted intensity and phase images is also studied with variations of the encrypted keys. The obtained results show that the proposed encryption scheme is feasible and has better security performance and robustness.

Based on the chaos and phase retrieval algorithm, a hierarchical multiple binary image encryption is proposed. In the encryption process, each plaintext is encrypted into a diffraction intensity pattern by two chaos-generated random phase masks (RPMs). Thereafter, the captured diffraction intensity patterns are partially selected by different binary masks and then combined together to form a single intensity pattern. The combined intensity pattern is saved as ciphertext. For decryption, an iterative phase retrieval algorithm is performed, in which a support constraint in the output plane and a median filtering operation are utilized to achieve a rapid convergence rate without a stagnation problem. The proposed scheme has a simple optical setup and large encryption capacity. In particular, it is well suited for constructing a hierarchical security system. The security and robustness of the proposal are also investigated.

Devil׳s vortex Fresnel lens phase masks on an asymmetric cryptosystem based on phase-truncation in gyrator wavelet transform domain

Full Poincaré beams, which cover all polarization states on the Poincaré sphere, provide a unique and complete degree of freedom for polarization manipulation in optical encryption. This paper introduces a novel optical image encryption method based on double random phase encoding (DRPE) system with multi-dimensional keys of full Poincaré beam. The encryption process begins by preprocessing the full Poincaré beam with a polarizer, followed by loading the image to be encrypted along this polarization direction, and finally performing encryption via the DRPE system. The scheme integrates conventional optical keys, such as wavelength, topological charge, amplitude, and phase, with the complete polarization dimension afforded by the full Poincaré beam, as well as the spatial loading dimension of the image placed behind the lens. By synergistically combining these multi-dimensional keys, the encryption system significantly expands the key space. Additionally, the dual random phase modulation capability of the DRPE system further enhances information security. This work establishes a new paradigm for high-security optical encryption.

DNA Cryptography is one of new algortihm in cryptography that is used to encrypt the data by converting the DNA code into binary code. Encryption process is expected to produce a random and unreadable ciphertext. This research aims to determine the result of encryption frequency analysis of the ciphertext obtained from the encryption process using DNA Cryptography and Digraph Transformation algorithm. The formation of a symmetric key is carried out for the encryption and decryption process in DNA Cryptography, and modular arithmetic in Digraph Transformation algorithm. The encryption process produces ciphertext in the form of letters and symbols because if involves the use of an ASCII table. Frequency analysis is done by comparing the frequency of occurence of letters in the ciphertext with frequency of occurence of letters in English. The conclusion for this research is that the ciphertext looks random, not easy to read, and hard to guess. For the future work, researcher can change the choice of binary code combinatory in DNA Cryptographic algorithms, increase the character vocabulary in the Digraph Transformation algorithm, and use various languages to code.

Advanced encryption and decryption strategies are of great significance for information protection and data security. Visual optical information encryption and decryption technology plays an important role in the field of information security. However, the current optical information encryption technologies have shortcomings such as the need for external decryption equipment, the inability to read out repeatedly, and information leakage, which hinder their practical application. By combining the excellent thermal response characteristics of the MXene-isocyanate propyl triethoxy silane (IPTS)/polyethylene (PE) bilayer and the structural color generated from the laser fabricated biomimetic structural color surface, an approach of encrypt, decrypt, and transmit information has been proposed. The microgroove-induced structural color is attached to the MXene-IPTS/PE bilayer to form a colored soft actuator (CSA) to realize information encryption and decryption, and information transmission. Benefiting from the unique photon-thermal response of the bilayer actuator and the precise spectrum response of the microgroove-induced structural color, the information encryption and decryption system has the advantages of being simple and reliable, which has the potential application in the field of optical information security.

A novel asymmetric multiple-image encryption method using an octonion Fresnel transform (OFST) and a two-dimensional Sine Logistic modulation map (2D-SLMM) is presented. First, a new multiple-image information processing tool termed the octonion Fresneltransform is proposed, and then an efficient method to calculate the OFST of an octonion matrix is developed. Subsequently this tool is applied to process multiple plaintext images, which are represented by octonion algebra, holistically in a vector manner. The complex amplitude, formed from the components of the OFST-transformed original images and modulated by a random phase mask (RPM), is used to derive the ciphertext image by employing an amplitude- and phase-truncation approach in the Fresnel domain. To avoid sending whole RPMs to the receiver side for decryption, a random phase mask generation method based on SLMM, in which only the initial parameters of the chaotic function are needed to generate the RPMs, is designed. To enhance security, the ciphertext and two decryption keys produced in the encryption procedure are permuted by the proposed SLMM-based scrambling method. Numerical simulations have been carried out to demonstrate the proposed scheme's validity, high security, and high resistance to various attacks.

Protection to classified digital data becomes so important in avoiding data manipulation and alteration. The focus of this paper is in data and information protection of digital images form. Protection is provided in the form of encrypted digital image. The encryption process uses a new map, , which is called MS map. This paper will show: the results of digital image encryption using MS map and how the performance is regarding the average time needed for encryption/decryption process; randomness of key stream sequence with NIST test, histogram analysis and goodness of fit test, quality of the decrypted image by PSNR, initial value sensitivity level, and key space. The results show that the average time of the encryption process is relatively same as the decryption process and it depends to types and sizes of the image. Cipherimage (encrypted image) is uniformly distributed since: it passes the goodness of fit test and also the histogram of the cipherimage is flat; key stream, that are generated by MS map, passes frequency (monobit) test, and runs test, which means the key stream is a random sequence; the decrypted image has same quality as the original image; and initial value sensitivity reaches 10−17, and key space reaches 3.24 × 10634. So, that encryption algorithm generated by MS map is more resistant to brute-force attack and known plaintext attack.

This paper designs an encryption and decryption system based on the FPGA. The system uses AES algorithm to encrypt and decrypt data. A pipeline IP core is designed with the reconfigurable technology complying with the Avalon bus interface specification. The IP core is applied to be a custom component on Nios II architecture so that the encryption and decryption processes through hardware can be controlled by software. Finally, the program is downloaded to the Altera DE2 development board and completes the testing of encryption and decryption processes. The system can be widely implemented in the field of data security.