Optical image encryption using improper Hartley transforms and chaos

We propose a new method for image encryption using improper Hartley transform and chaos theory. Improper Hartley transform is a Hartley transform in which the phase between the two Fourier transforms is a fractional multiple of π/2. This fractional order is called fractional parameter and serves as a key in the image encryption and decryption process. Four types of chaos functions have been used. These functions are the logistic map, the tent map, the Kaplan-Yorke map and the Ikeda map. Random intensity masks have been generated using these chaotic functions and are called chaotic random intensity masks. The image is encrypted by using improper Hartley transform and two chaotic random intensity masks. The mean square error has been calculated. The robustness of the proposed technique in terms of blind decryption has been tested. The computer simulations are presented to verify the validity of the proposed technique.     

基于分频域和菲涅耳域的光学图像加密方法

结合分数傅里叶变换及菲涅耳变换,在光学图像加密系统中分别具有多密钥性和无透镜性的优点,提出了基于分频域和菲涅耳域的光学图像加密方法。基于分数傅里叶变换的光学加密系统,引入菲涅耳变换及全息技术,使原有的加密系统在不增加光学元件的基础上提高了系统的安全性。理论分析和计算机仿真模拟证明了这种方法的可行性。     

Optical image encryption based on binary Fourier transform computer-generated hologram and pixel scrambling technology

A new method of optical image encryption with binary Fourier transform computer-generated hologram (CGH) and pixel-scrambling technology is presented. In this method, the orders of the pixel scrambling, as well as the encrypted image, are used as the keys to decrypt the original image. Therefore, higher security is achieved. Furthermore, the encrypted image is binary, so it is easy to be fabricated and robust against noise and distortion. Computer simulation results are given to verify the feasibility of this method and its robustness against occlusion and additional noise.     

Chaotic encryption and decryption of JPEG image

According to encrypting principles of digital images, integrating the characteristic of JPEG image, and using discrete chaotic sequence, this paper has studied encryption and decryption of JPEG image, and has compared and analyzed the corresponding relations between the encryption and decryption effects and their security of two different encrypting schemes of the JPEG image chaotic encryption studied by this paper. In a basic unit of an 8 × 8 data block, image encryption and decryption not only are fast, but also match with JPEG format. The JPEG image encryption can meet the security requirement of the storage and transmission of JPEG images in some common application occasions, and provides an effective and feasible way of encrypting JPEG images.     

A novel color image encryption scheme using alternate chaotic mapping structure

This paper proposes an color image encryption algorithm using alternate chaotic mapping structure. Initially, we use the R, G and B components to form a matrix. Then one-dimension logistic and two-dimension logistic mapping is used to generate a chaotic matrix, then iterate two chaotic mappings alternately to permute the matrix. For every iteration, XOR operation is adopted to encrypt plain-image matrix, then make further transformation to diffuse the matrix. At last, the encrypted color image is obtained from the confused matrix. Theoretical analysis and experimental results has proved the cryptosystem is secure and practical, and it is suitable for encrypting color images.     

Digital image encryption with chaotic map lattices

This paper proposes a secure approach for encryption and decryption of digital images with chaotic map lattices. In the proposed encryption process,eight different types of operations are used to encrypt the pixels of an image and one of them will be used for particular pixels decided by the outcome of the chaotic map lattices. To make the cipher more robust against any attacks,the secret key is modified after encrypting each block of sixteen pixels of the image. The experimental results and security analysis show that the proposed image encryption scheme achieves high security and efficiency.     

Chaos-based partial image encryption scheme based on linear fractional and lifting wavelet transforms

In this paper, a new chaos-based partial image encryption scheme based on Substitution-boxes (S-box) constructed by chaotic system and Linear Fractional Transform (LFT) is proposed. It encrypts only the requisite parts of the sensitive information in Lifting-Wavelet Transform (LWT) frequency domain based on hybrid of chaotic maps and a new S-box. In the proposed encryption scheme, the characteristics of confusion and diffusion are accomplished in three phases: block permutation, substitution, and diffusion. Then, we used dynamic keys instead of fixed keys used in other approaches, to control the encryption process and make any attack impossible. The new S-box was constructed by mixing of chaotic map and LFT to insure the high confidentiality in the inner encryption of the proposed approach. In addition, the hybrid compound of S-box and chaotic systems strengthened the whole encryption performance and enlarged the key space required to resist the brute force attacks. Extensive experiments were conducted to evaluate the security and efficiency of the proposed approach. In comparison with previous schemes, the proposed cryptosystem scheme showed high performances and great potential for prominent prevalence in cryptographic applications.     

Novel single-channel color image encryption algorithm based on chaos and fractional Fourier transform

A new color image encryption algorithm based on fractional Fourier transform (FrFT) and chaos is proposed. The colors of the original color image are converted to HSI (hue-saturation-intensity), and the S component is transformed by the random-phase encoding based on FrFT to obtain a new random phase. The I component is transformed by double random-phase encoding based on FrFT using the H component and the new random phase as two phase plates. Then chaos scrambling technology is used to encrypt the image, which makes the resulting image nonlinear and disorder both in spatial domain and frequency domain. Additionally, the ciphertext is not a color image but a combination of a gray image and a phase matrix, so the ciphertext has camouflage property to some extent. The results of numerical simulations demonstrate the effectiveness and the security of this algorithm.     

Signal separation using linear canonical and fractional Fourier transforms

Signal separation is an important operation in many areas such as communications, geophysics, and optics including optical signal processing. In this article, the issue of signal separation based on the linear canonical transform (LCT) and the fractional Fourier transform (FRFT) is considered. An iterative algorithm for signal separation in the 2-ray ground reflected model using the FRFT is also presented along with the simulation results.     

Optical image encryption using Hartley transform and logistic map

We propose a new method for image encryption using Hartley transform with jigsaw transform and logistic map. Logistic map has been used to generate the random intensity mask which is known as chaotic random intensity mask. The problem of bare decryption with Hartley transform has been solved by using the jigsaw transform. In the proposed technique, the image is encrypted using two methods in which the second method is the extension of the first method. In the first method, the image is encrypted using Hartley transform and jigsaw transform. In the second method, the image is encrypted using Hartley transform, jigsaw transform and logistic map. The mean square errors and the signal to noise ratio have been calculated. Robustness of the technique in terms of blind decryption and the algorithmic complexity has been evaluated. The optical implementation has been proposed. The computer simulations are presented to verify the validity of the proposed technique.     

Novel image encryption algorithm based on cycle shift and chaotic system

In this paper, a novel image encryption algorithm is proposed. The cycle shift in bits of pixels and the chaotic system are employed for the encryption of the proposed scheme. For cycle shift operations, random integers with the same size of the original image are produced to scramble the plaintext image. Moreover, the scrambled image effects the initial values of the chaotic system for the further encryption process, which increases the sensitivity of plaintext images of the scheme. The scrambled image is encrypted into the ciphered image by the keys which are produced by the chaotic system. The simulation experiments and theoretical analyses indicate that the proposed scheme is superior and able to resist exhaustive attack and statistical attack.     

Cryptanalysis of a new image encryption algorithm based on hyper-chaos

This Letter proposes two different attacks on a recently proposed image based on hyper-chaos. The cryptosystem under study proceed first by shuffling the image rows and columns to disturb the high correlation among pixels by iterating the logistic map. Second, a keystream is generated to mix it with the pixels of the shuffled image using hyper-chaos. These two processes in the encryption stage present weakness, and a chosen plaintext attack and a chosen ciphertext attack can be done to recover the ciphered-image without any knowledge of the key value. It just demands three couples of plaintext/ciphertext to break totally the cryptosystem.     

A novel image encryption method based on total shuffling scheme

In this paper, a novel image encryption method based on skew tent chaotic map and permutation-diffusion architecture is proposed. In the proposed method, the P-box is chosen as the same size of plain-image, which shuffles the positions of pixels totally. The keystream generated by skew tent chaotic map is related to the plain-image. Statistical analysis, information entropy analysis, and sensitivity analysis to plaintext and key on the proposed scheme are provided in this paper. It can be seen that this algorithm is efficient and reliable, with high potential to be adopted for network security and secure communications.     

Multiple-image encryption algorithm based on mixed image element and permutation

To improve encryption efficiency and facilitate the secure transmission of multiple digital images, by defining the pure image element and mixed image element, this paper presents a new multiple-image encryption (MIE) algorithm based on the mixed image element and permutation, which can simultaneously encrypt any number of images. Firstly, segment the original images into pure image elements; secondly, scramble all the pure image elements with the permutation generated by the piecewise linear chaotic map (PWLCM) system; thirdly, combine mixed image elements into scrambled images; finally, diffuse the content of mixed image elements by performing the exclusive OR (XOR) operation among scrambled images and the chaotic image generated by another PWLCM system. The comparison with two similar algorithms is made. Experimental results and algorithm analyses show that the proposed MIE algorithm is very simple and efficient, which is suitable for practical image encryption.     

A novel bit-level image encryption algorithm based on chaotic maps

Recently, a number of chaos-based image encryption algorithms have been proposed at the pixel level, but little research at the bit level has been conducted. This paper presents a novel bit-level image encryption algorithm that is based on piecewise linear chaotic maps (PWLCM). First, the plain image is transformed into two binary sequences of the same size. Second, a new diffusion strategy is introduced to diffuse the two sequences mutually. Then, we swap the binary elements in the two sequences by the control of a chaotic map, which can permute the bits in one bitplane into any other bitplane. The proposed algorithm has excellent encryption performance with only one round. The simulation results and performance analysis show that the proposed algorithm is both secure and reliable for image encryption.     

基于物理混沌的混合图像加密系统研究

初步实现了基于物理混沌的混沌和数据加密标准算法级联的混合图像加密系统,基于该系统研究了级联加密与单级加密的抗统计分析能力,以及不可预测性强弱不同的混沌信号在该系统中应用时密文特性的不同.这种利用物理混沌不可预测性的混合加密系统,不存在确定的明文密文映射关系,而且密文统计特性也应优于(或大致相当)其他加密系统.数值结果支持这一结论,同时表明不可预测性较强的混沌系统其加密产生的密文相关性较弱.     

基于非对称密码系统的彩色图像加密技术

为了实现对彩色图像的加密,提出一种基于傅里叶变换和非对称密钥加密系统的加密方法。把彩色图像分成三基色分量:红,绿,蓝。然后对这3帧灰度图像的傅里叶频谱进行截取,合成一个目标图像,该目标图像包含了原始彩色图像的大部分信息。对此目标图像的幅度和相位分别用非对称密钥加密系统加密,即实现了彩色图像的加密。 给出了理论分析和计算机模拟结果,实验结果证实了该方法的可行性。     

Optical image encryption using fractional Fourier transform and chaos

We propose a new method for image encryption using fractional Fourier transform and chaos theory. Random phase masks are generated using iterative chaos functions. The input image is combined with the first random phase mask at the object plane and is then transformed using the fractional Fourier transform. After the first fractional Fourier transform, the second random phase mask, again generated by using the chaos functions, is used at the fractional plane. The second fractional Fourier transform operation is then carried out to obtain the encrypted image. Three types of chaos functions have been used: the logistic map, the tent map and the Kaplan–Yorke map. The mean square error and the signal-to-noise ratio between the decrypted image and the input image for the correct order and the incorrect order of the fractional Fourier transform have been calculated. The computer simulations are presented to verify the validity of the proposed technique.     

Optical hyperspectral data encryption in spectrum domain by using 3D Arnold and gyrator transforms

In this letter, a hyperspectral image encryption algorithm based on 3D Arnold transform and gyrator transform in spectrum domain is proposed. First, the original hyperspectral cube will be scrambled by 3D Arnold transform in the spatial domain. Subsequently, the obtained intermediate data are converted into spectrum domain to create a new spectral image. This new spectral image is decomposed into numerous single pieces and encoded using gyrator transform. The corresponding decrypted hyperspectral cube can be recovered by performing along the reverse direction of the encryption process. Some numerical simulations have been performed to verify the validity and capability of the proposed hyperspectral encryption algorithm.     

A fast image encryption method by using chaotic 3D cat maps

An image encryption method using a chaotic 3D cat map is presented in this paper. The process of the proposed algorithm contains the simultaneous operations of pixels’ locations permutation and pixels’ values substitution at every iterative step of the chaotic map, which making the forward and reverse encryption needs only one traverse of the image pixels. Moreover, a perturbation is introduced to eliminate the undesirable finite precision effect of computer in realization. The main advantages of such a secure method are the simplicity and efficiency. Both simulations and analysis show the proposed algorithm can produce a large key space and resist the common existing cipher attacks. These good cryptographic properties make it suitable for image applications.