一种保持非负整数值的图像加密算法

提出了一种能够使双随机相位图像加密方法的密文图像保持为非负整数值的变换——重构变换.重构变换包括预处理和频谱搬移两个过程,其主要特点为,在图像进行频域变换之前,通过叠加的方式将整数图像压缩成一半大小的复数图像,从而能缩小后续运算的计算空间;基于重构变换的双随机相位图像加密方法可以实现联合图像压缩和加密的效果.与基于混沌系统的数字图像加密方法相比,本文方法的密文图像具有更低的信息熵.实验结果表明,该方法具有较强的安全性,解密图像基本无失真,并且密文图像对加性噪音攻击具有一定的鲁棒性.     

基于多混沌系统的双图像光学加密算法

为了扩展双图像光学加密算法的密钥空间,克服双随机相位加密系统中随机相位掩模作为密钥难于存储、传输和重构的问题,突破传统图像加密的研究思路,提出了一种基于多混沌系统的双图像加密算法,构造了光学加密系统。系统增加混沌系统参数作为密钥,利用混沌加密密钥空间大和图像置乱隐藏性好的特点,构建基于Logistic混沌映射的图像置乱算法,利用Kent混沌映射生成的伪随机序列构造出一对随机相位掩模,分别放置在分数傅里叶变换光学装置的两端,图像经加密系统变换后得到密文。数值仿真结果表明,算法的密钥敏感性极高,能够有效地对抗统计攻击,具有较高的安全性。     

一种基于迭代振幅-相位恢复算法和非线性双随机相位编码的图像加密方法

提出了一种基于迭代振幅-相位恢复算法和非线性双随机相位编码的图像加密方法。该方法利用两个公开密钥和一幅"假图像"在非线性双随机相位加密系统中生成密文,接着利用迭代非线性双随机相位编码生成两个私有密钥。待加密图像和密文作为迭代加密方法中的两个限定值。解密过程则可以在经典的基于4f系统的线性的光学双随机相位编码系统中完成。该加密方法具有迭代收敛速度快、安全性高的优点。迭代该图像加密方法能够抵御最近提出的基于改进的振幅-相位恢复算法的攻击。理论分析和仿真实验都证明了此方法的有效性和可靠性。     

基于双随机相位编码的非线性双图像加密方法

提出了一种基于双随机相位编码技术的非线性双图像加密方法,并分析了其安全性。在该方法中,加密过程和解密过程以及加密密钥和解密密钥均不相同。加密过程具有非线性,解密过程则是线性的。将两幅待加密图像复合为复振幅图像,并利用双随机相位编码技术和切相傅里叶变换进行加密,加密过程中生成两个解密密钥,解密过程则在经典的基于4f系统的双随机相位编码系统中完成。相比经典的双随机相位加密技术和基于切相傅里叶变换的单图像加密技术,该加密方法的安全性更高,它能够抵御最近提出的基于两步振幅相位恢复算法的特定攻击。理论分析和仿真实验结果都证明了此加密方法的可行性和安全性。     

双随机相位加密系统的选择明文攻击

在光学信息安全领域,双随机相位加密方法最引人注目并得到广泛研究,但由于双随机相位加密系统是基于傅里叶变换的系统,其本质上是一种线性变换系统,明文、密文之间的函数依赖关系比较简单,这就为其安全性留下了很大的隐患。双随机相位加密方法可以用光学和数字的方式实现,提出了一种选择明文攻击的方法,利用多个冲击函数作为选择的明文,成功破解了基于数字方法实现的双随机相位加密系统,并给出了恢复密钥的解析式,此方法最大的优点在于解密图像的无损性,并从理论上加以证明,给出了实验结果。     

用多重菲涅耳衍射变换和相位密码板实现图像加密的技术

基于多重菲涅耳衍射变换和相位密码板,设计了一种新的图像加密计算方法.待加密的明文图像在多重离散菲涅耳衍射变换和相位密码板的共同作用下,变换为一个具有随机码特征的密文矩阵;衍射距离和相位密码板是主要的密钥.只有当所有密钥都正确时,才能成功地解密密文.结果表明,该加密算法能抵抗JPEG有损压缩、图像剪切、重度噪音污染和重采样等攻击,因此该法具有较强的鲁棒性;由于很难破解多重密钥,所以该算法具有极高的安全性.     

基于稀疏相位和可调傅里叶变换的图像加密

针对光学图像加密的轮廓显现问题,提出了一种基于稀疏相位和可调傅里叶变换的图像加密方法。将可调傅里叶变换引入光学图像加密程序中,运用二维可调傅里叶变换实现像素混淆处理,相比基于复数或实数的变换域方案,计算复杂度较低;从加密函数提取相位值并获得加密数据的相位函数,再提取相位加密函数的稀疏数据,从而避免将密文相位信息主要集中在纯相位掩码内,以解决轮廓显现问题;完成了单图像加密实验和双图像加密实验,结果表明实现了较好的安全性,解决了光学图像加密的轮廓显现问题。     

基于矢量运算和副像相位掩模的遥感图像加密技术

针对遥感图像及彩色图像传输过程中的信息安全问题,提出了一种利用矢量运算和副像相位掩模对彩色遥感图像加密的方法.在加密过程中,利用光学相干叠加原理将原始图像矢量分解,并叠加到R、G、B三个通道上的两个相位板当中;然后,使用副像相位掩模在菲涅尔域中双随机相位编码对其中一个相位板加密;最后,利用两个随机矩阵的Kronecker积对编码图像进行进一步随机化处理,实现彩色遥感图像的多级加密.实验结果表明:该算法的密钥敏感度高,在强度系数小于0.04的高斯噪声攻击和统计分析攻击下具有良好的稳健性;密文能够抵御选择明文攻击,相比于传统的双随机相位编码算法具有更强的安全性.解密遥感图像的峰值信噪比和相关系数可达31.92dB和0.9888.该加密方法为大量相同尺寸遥感图像的加密提供了新的思路.     

基于压缩感知的光学图像加密技术研究

提出了一种基于压缩感知的光学数字图像加密方案,利用压缩感知理论及特点,借助双随机相位编码技术,实现了对数字图像的多重加密。通过压缩感知使用随机测量矩阵作为密钥对原始图像加密,然后对加密图像利用Arnold变换置乱二次加密,并通过4f光学系统进行双随机相位编码再次对图像加密,从而实现了对图像的多次加密。考虑实际应用中传输过程的安全性,将加密图像融合于载体图像。在接收端,对加密图像进行解密重构。实验结果表明,该加密方案能够有效降低采样数据量,具有高稳健性,对密钥响应敏感并可以抵御较强的攻击。     

基于离散四元数傅里叶变换的双随机相位加密技术

应用光学图像加密的思想,将离散四元数傅里叶变换(DQFT)与双随机相位加密技术相结合,提出了一种应用于彩色图像的双随机相位加密新技术. 基于DQFT的双随机相位加密技术可将彩色图像作为一个整体进行加密,从而在保持了系统的保密性能的同时,有效地降低了复杂性. 阐述了加密和解密的原理,并通过实验对其鲁棒性进行了验证. 关键词： 四元数 离散四元数傅里叶变换(DQFT) 双随机相位加密     

Single Channel Quantum Color Image Encryption Algorithm Based on HSI Model and Quantum Fourier Transform

In order to obtain high-quality color images, it is important to keep the hue component unchanged while emphasize the intensity or saturation component. As a public color model, Hue-Saturation Intensity (HSI) model is commonly used in image processing. A new single channel quantum color image encryption algorithm based on HSI model and quantum Fourier transform (QFT) is investigated, where the color components of the original color image are converted to HSI and the logistic map is employed to diffuse the relationship of pixels in color components. Subsequently, quantum Fourier transform is exploited to fulfill the encryption. The cipher-text is a combination of a gray image and a phase matrix. Simulations and theoretical analyses demonstrate that the proposed single channel quantum color image encryption scheme based on the HSI model and quantum Fourier transform is secure and effective.     

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 3D image encryption technique using computer-generated integral imaging and cellular automata transform

A novel three-dimensional (3D) image encryption approach by using the computer-generated integral imaging and cellular automata transform (CAT) is proposed, in which, the two-dimensional (2D) elemental image array (EIA) digitally recorded by light rays coming from the 3D image is mapped inversely through the virtual pinhole array according to the ray-tracing theory. Next, the encrypted image is generated by using the 2D CAT scrambling transform for the 2D EIA. The reconstructed process is carried out by using the modified computational integral-imaging reconstruction (CIIR) technique; the depth-dependent plane images are reconstructed on the output plane. The reconstructed 3D image quality of the proposed scheme can be greatly improved, because the proposed encryption scheme carries out in a computer which can avoid the light diffraction caused by optical device CIIR, and solves blur problem caused by CIIR by using the pixel-averaging algorithm. Furthermore, the CAT-based encryption algorithm is an error-free encryption method; CAT as an orthogonal transformation offers considerable simplicity in the calculation of the transform coefficient, that is, it can improve the quality of the reconstructed image by reducing energy loss compared with the traditional complicated transform process. To show the effectiveness of the proposed scheme, we perform computational experiments. Experimental results show that the proposed scheme outperforms conventional encryption methods.     

Phase image encryption in the fractional Hartley domain using Arnold transform and singular value decomposition

A novel scheme for image encryption of phase images is proposed, using fractional Hartley transform followed by Arnold transform and singular value decomposition in the frequency domain. Since the plaintext is a phase image, the mask used in the spatial domain is a random amplitude mask. The proposed scheme has been validated for grayscale images and is sensitive to the encryption parameters such as the order of the Arnold transform and the fractional orders of the Hartley transform. We have also evaluated the scheme's resistance to the well-known noise and occlusion attacks.     

Ghost imaging-based optical cryptosystem for multiple images using integral property of the Fourier transform

A novel ghost imaging-based optical cryptosystem for multiple images using the integral property of the Fourier transform is proposed. Different from other multiple-image encryption schemes, we mainly construct the modulation patterns related to the plaintext images to realize the encrypted transmission of multiple images. In encryption process, the first image is encrypted by the ghost imaging encryption scheme, and the intensity sequence obtained by the bucket detector is used as the ciphertext. Then modulation patterns of other images are constructed by using the integral property of the Fourier transform and used as the keys. Finally, the ciphertext and keys are transmitted to the receiver to complete the encryption process. During decryption, the receiver uses different keys to decrypt the ciphertext and gets different plaintext images, and decrypted images have no image aliasing problem. Experiments and simulations verify the feasibility, security, and robustness of the proposed scheme. This scheme has high scalability and broad application prospect, which provides a new idea for optical information encryption.     

Single-channel color image encryption using phase retrieve algorithm in fractional Fourier domain

A single-channel color image encryption is proposed based on a phase retrieve algorithm and a two-coupled logistic map. Firstly, a gray scale image is constituted with three channels of the color image, and then permuted by a sequence of chaotic pairs generated by the two-coupled logistic map. Secondly, the permutation image is decomposed into three new components, where each component is encoded into a phase-only function in the fractional Fourier domain with a phase retrieve algorithm that is proposed based on the iterative fractional Fourier transform. Finally, an interim image is formed by the combination of these phase-only functions and encrypted into the final gray scale ciphertext with stationary white noise distribution by using chaotic diffusion, which has camouflage property to some extent. In the process of encryption and decryption, chaotic permutation and diffusion makes the resultant image nonlinear and disorder both in spatial domain and frequency domain, and the proposed phase iterative algorithm has faster convergent speed. Additionally, the encryption scheme enlarges the key space of the cryptosystem. Simulation results and security analysis verify the feasibility and effectiveness of this method.     

Color image encryption by using Arnold transform and color-blend operation in discrete cosine transform domains

A color image encryption algorithm is designed by use of Arnold transform and discrete cosine transform (DCT). The RGB components of the color image are scrambled by Arnold transform at the aspect of pixel sequence. The scrambled RGB components are exchanged and mixed randomly under the control of a matrix defined by random angle. DCT is employed for changing the pixel values of color image. In this encryption scheme the operations mentioned above are performed twice continuously. The parameters of Arnold transform and the random angle serve as the key of the color image encryption method. Some numerical simulations are made to test the validity and capability of the color encryption algorithm.     

Cascaded Fresnel holographic image encryption scheme based on a constrained optimization algorithm and Henon map

We propose an image encryption scheme using chaotic phase masks and cascaded Fresnel transform holography based on a constrained optimization algorithm. In the proposed encryption scheme, the chaotic phase masks are generated by Henon map, and the initial conditions and parameters of Henon map serve as the main secret keys during the encryption and decryption process. With the help of multiple chaotic phase masks, the original image can be encrypted into the form of a hologram. The constrained optimization algorithm makes it possible to retrieve the original image from only single frame hologram. The use of chaotic phase masks makes the key management and transmission become very convenient. In addition, the geometric parameters of optical system serve as the additional keys, which can improve the security level of the proposed scheme. Comprehensive security analysis performed on the proposed encryption scheme demonstrates that the scheme has high resistance against various potential attacks. Moreover, the proposed encryption scheme can be used to encrypt video information. And simulations performed on a video in AVI format have also verified the feasibility of the scheme for video encryption.     

离散Arnold变换改进及其在图像置乱加密中的应用

为了改善传统二维Arnold变换用于图像置乱加密的效果,提出了离散Arnold变换的改进方法,并将其用于图像置乱加密测试研究.该方法利用现有离散标准映射的构造思想,将传统离散二维Arnold变换表达式中第一个变换表达式所对应变换结果非线性融入第二个变换表达式,实现经典离散二维Arnold变换的非线性去拟仿射化修改,以便快速改善图像置乱加密效果.数学证明改进方法不再保持现有离散二维Arnold变换所具有的拟仿射不变性,但是改进变换仍是一种具有周期性的可逆映射,将其用于图像置乱加密时,利用其周期性或逆变换能恢复置乱前原图像.大量实验结果表明,本文所建议的改进方法是有效的,相比现有的离散Arnold变换更具有实用价值意义.