Optical noise-free image encryption based on quick response code and high dimension chaotic system in gyrator transform domain

A novel optical image encryption scheme is proposed based on quick response code and high dimension chaotic system, where only the intensity distribution of encoded information is recorded as ciphertext. Initially, the quick response code is engendered from the plain image and placed in the input plane of the double random phase encoding architecture. Then, the code is encrypted to the ciphertext with noise-like distribution by using two cascaded gyrator transforms. In the process of encryption, the parameters such as rotation angles and random phase masks are generated as interim variables and functions based on Chen system. A new phase retrieval algorithm is designed to reconstruct the initial quick response code in the process of decryption, in which a priori information such as three position detection patterns is used as the support constraint. The original image can be obtained without any energy loss by scanning the decrypted code with mobile devices. The ciphertext image is the real-valued function which is more convenient for storing and transmitting. Meanwhile, the security of the proposed scheme is enhanced greatly due to high sensitivity of initial values of Chen system. Extensive cryptanalysis and simulation have performed to demonstrate the feasibility and effectiveness of the proposed scheme.     

Multiple information encryption by user-image-based gyrator transform hologram

A novel multiple information encryption by user-image-based gyrator transform hologram is proposed. In encryption process, each channel of the user image is phase encoded, modulated by random phase function and then gyrator transformed to get the gyrator spectrum of user image. Subsequently, each channel of the secret image is normalized, phase encoded, multiplied by modulated user image, and then gyrator transformed to obtain the gyrator spectrum of secret image. The encrypted digital hologram is recorded by the interference between the gyrator spectrum of user image and the spherical wave function. Similarly, the digital hologram for decryption is recorded by the interference between the gyrator spectrum of secret image and the spherical wave function. The multiple encrypted digital holograms are multiplexed into a final encoded hologram and the corresponding digital holograms for decryption are multiplexed into a final hologram for decryption. The wavelength and radius of the spherical wave function, and angle of gyrator transform are all essential keys for decryption. The proposed system has two main features. First, the encrypted hologram has no information about secret image. Second, the hologram for decryption used as identification key. Consequently the two marked security layers of information protection are achieved. The proposal can be realized by optoelectronic system. Numerical simulation results demonstrate the feasibility and security of the proposed technique.     

Triple color images encryption algorithm based on scrambling and the reality-preserving fractional discrete cosine transform

An image encryption algorithm to secure three color images simultaneously by combining scrambling with the reality-preserving fractional discrete cosine transform (RPFrDCT) is proposed. The three color images to be encrypted are converted to their indexed formats by extracting their color maps, which can be considered as the three components of a color image. These three components are affected each other by scrambling the interims obtained from vertically and horizontally combining the three indexed formats with the help of the chaos-based cyclic shift. The three scrambled components are separately transformed with the RPFrDCT, in which the generating sequences are determined by the Chirikov standard chaotic map. Arnold transform is used to further enhance the security. Due to the inherent properties of the chaotic maps, the cipher keys are highly sensitive. Additionally, the cipher image is a single color image instead of three color ones, and is convenient for display, storage and transmission due to the reality property of RPFrDCT. Numerical simulations are performed to show the validity of the proposed algorithm.     

An image encryption scheme using generalized Arnold map and affine cipher

This paper aims to provide an image encryption scheme with an efficient bit-level permutation and a pixel-level diffusion procedure. In the bit-level permutation, we divide each pixel into 8 bits, and arrange the positions of each bit by the generalized Arnold map in row and column direction. Hence, a significant diffusion effect is happened in the bit-level permutation. In the pixel-level diffusion procedure, we apply affine cipher to change the gray value and the histogram distribution of the permutated image. Various types of security analyses demonstrate that the proposed scheme is competitive with that ordinary permutation–diffusion type image cipher and proper for practical image encryption.     

Quantum Secure Dialogue with Quantum Encryption

How to solve the information leakage problem has become the research focus of quantum dialogue. In this paper, in order to overcome the information leakage problem in quantum dialogue, a novel approach for sharing the initial quantum state privately between communicators, i.e., quantum encryption sharing, is proposed by utilizing the idea of quantum encryption. The proposed protocol uses EPR pairs as the private quantum key to encrypt and decrypt the traveling photons, which can be repeatedly used after rotation. Due to quantum encryption sharing, the public announcement on the state of the initial quantum state is omitted, thus the information leakage problem is overcome.The information-theoretical efficiency of the proposed protocol is nearly 100%, much higher than previous information leakage resistant quantum dialogue protocols. Moreover, the proposed protocol only needs single-photon measurements and nearly uses single photons as quantum resource so that it is convenient to implement in practice.     

An image encryption algorithm based on spatiotemporal chaos and middle order traversal of a binary tree

This paper proposes an image encryption algorithm based on spatiotemporal chaos and middle order traversal of a binary tree. Firstly, other programming software is used to perform the middle order traversal, and the plaintext image is sorted according to the middle order traversal sequence on the permutation. Secondly, the chaotic sequence is generated using the coupled map lattice to set the chaotic interference value. Finally, the XOR operation between the adjacent pixel values of the replacement image is completed to generate the ciphertext matrix. The simulation and experimental results show that the proposed algorithm can resist typical attacks and has good robustness.     

Degradative encryption: An efficient way to protect SPIHT compressed images

Degradative encryption, a new selective image encryption paradigm, is proposed to encrypt only a small part of image data to make the detail blurred but keep the skeleton discernible. The efficiency is further optimized by combining compression and encryption. A format-compliant degradative encryption algorithm based on set partitioning in hierarchical trees (SPIHT) is then proposed, and the scheme is designed to work in progressive mode for gaining a tradeoff between efficiency and security. Extensive experiments are conducted to evaluate the strength and efficiency of the scheme, and it is found that less than 10% data need to be encrypted for a secure degradation. In security analysis, the scheme is verified to be immune to cryptographic attacks as well as those adversaries utilizing image processing techniques. The scheme can find its wide applications in online try-and-buy service on mobile devices, searchable multimedia encryption in cloud computing, etc.     

基于相息图迭代的随机相位加密

提出了一种将随机相位加密和相位恢复算法中的求解附加相位分布分二步实施的加密方法. 由于该方法的实质是通过在随机谱和相息图之间进行相位恢复迭代以确定相息图和密钥的相 位分布，因而能够减小图像的解密误差.在相息图相位离散化的迭代过程中，采用增大设计 冗余度的方法，降低了由相位离散化所带来的解密误差.最后，通过计算机模拟实验验证了 该方法在减小图像解密误差方面的有效性. 关键词： 随机相位 光学图像加密 相息图 二元光学 离散化误差 相位恢复算法     

An Image Compression Encryption Algorithm Based on Chaos and ZUC Stream Cipher

In order to improve the transmission efficiency and security of image encryption, we combined a ZUC stream cipher and chaotic compressed sensing to perform image encryption. The parallel compressed sensing method is adopted to ensure the encryption and decryption efficiency. The ZUC stream cipher is used to sample the one-dimensional chaotic map to reduce the correlation between elements and improve the randomness of the chaotic sequence. The compressed sensing measurement matrix is constructed by using the sampled chaotic sequence to improve the image restoration effect. In order to reduce the block effect after the parallel compressed sensing operation, we also propose a method of a random block of images. Simulation analysis shows that the algorithm demonstrated better encryption and compression performance.