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。     

一种混合混沌虚拟光学图像加密方法

用共参数的两种混沌系统生成可置换传统双随机相位编码系统中随机相位模板的新模板.将明文图像编码为相位信息,克服原双随机相位编码系统对第一块相位模板不敏感的缺陷;构建可产生均匀非相关随机序列的广义Fibonacci混沌系统,生成均匀分布的相位模板进行图像加密,提高密钥传输效率及系统对密钥的敏感性;对一次加密得到的复值图像,采用提取其振幅及相位的替代操作进行再加密,解决其像素值不能通过按位"异或"进行替代的问题,使密文图像分布更均匀,信息熵达到7.995 8,能有效抵御统计分析攻击.在二次加密中,将产生加密模板的混沌初值与一次加密得到的密文联系,像素数改变率达到0.995 239,更接近理想期望值,增强了系统对明文的敏感性,有效抵御选择明文攻击.仿真实验表明,该方法有效增加了密钥空间和密钥敏感性,提高了加密系统加密效率和安全性.     

基于改进Logistic混沌映射的数字图像加密算法研究

混沌序列具有伪随机性、遍历性、对初始条件极其敏感性以及具备白噪声的统计特性等特点;文章利用Logistic混沌映射的改进算法产生的混沌序列所具有的这些特性,对数字图像进行空域像素进行位置置乱,然后对置乱后的图像序列按照一定的方法进行异或处理得到加密图像;实验在图像的竖直、水平、对角线方向,随机选择像素点,利用其灰度值,图像像素个数,计算数学期望,方差,协方差,相关系数;结果表明文章算法扰乱了图像像素间的相关性,使得加密图像能够抵抗明文统计的攻击,且密钥空间大,运算速度快,具有非常好的加密效果。     

Gyrator变换域下基于超混沌相位掩模的光学水印方法

针对光学变换水印算法中光学实现的轴对准问题和光学密码系统的安全性问题,提出一种基于超混沌映射和Gyrator变换的光学水印方法。利用Chen 4D超混沌系统构造超混沌相位掩模,然后通过菲涅耳波带板和径向希尔伯特掩模构造的涡旋光,对超混沌相位板进行照明,最后借助Gyrator变换将加密后的水印图像植入宿主灰度图像,实现Gyrator变换域下的光学信息隐藏。通过Gyrator逆变换提取目标图像中植入的水印信息。实验结果表明,该算法能够从高不可感知性的目标图像中提取高质量的水印信息,加密的目标图像信噪比高,与宿主图像的相关性强,能够有效地抵御强度系数为0.06和0.8的椒盐噪声和高斯噪声的攻击,对低于50%遮挡率和80压缩因子的攻击具有良好的稳健性。加密后的目标图像与原始宿主图像具有相似的统计分布,较好地实现了信息隐藏。     

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.     

基于量子随机行走和多维混沌的三维图像加密算法

随着互联网的发展,人们对于信息安全的需求日益增加,而经典的加密技术存在着密钥空间小、易破解的缺陷,图像加密技术在保护图像信息安全和隐私内容等方面的问题亟待解决.量子随机行走作为一种新型量子密钥生成器,其密钥空间大,与经典随机行走相比计算速度与安全性有着明显的提高.本文提出一种基于量子随机行走并涉及Lorenz和Rossler多维混沌的三维图像加密算法.首先应用高斯金字塔对图像进行处理然后按照一定比例将处理后的图像切割成4份;其次使用量子随机行走生成的随机序列与多维混沌中的Lorenz混沌系统生成的随机序列对分成的若干块子图像进行汉明距离计算然后进行合成,并且对图像RGB三通道之间进行欧氏距离计算;最后将汉明距离与欧式距离取余得到的序列值作为初始值输入多维混沌中的Rossler系统,生成随机序列作为密钥对图像的RGB通道进行异或操作得到加密后的图像,对应解密方案为加密过程逆过程.此外,本文采用基于离散余弦变换和奇异值分解的盲水印嵌入算法将水印信息嵌入到加密后的图像中,实现接收方可以通过提取水印,根据水印信息的完整性来判断传输过程中图像是否遭受到攻击破坏,如无遭受恶意攻击,则对图像进行解密...     

基于L-L级联混沌与矢量分解的无损压缩光学图像加密

为克服双随机相位编码的光学图像加密中,密钥、密文体积大、抗选择明密文能力弱的问题,提出了一种Logistic-Logistic级联混沌与矢量分解的无损压缩光学图像加密方法 .先隔空取样置乱将明文分成两块,再用干涉合成一块,最后放入双随机相位编码系统得到密文.置乱能够克服干涉后看到明文信息的缺点,增加了加密系统的安全性.干涉使得密文体积变为原来的一半,便于密文传输.单位等模矢量分解的解密方式避免了现有压缩方式存在的解密图像分辨率降低的问题.Logistic-Logistic级联混沌极大缩小了双随机相位编码的密钥体积,同时还解决了Logistic序列分布不均匀问题,提高了序列随机性,保留了Logistic混沌的快速性.将明文的HASH值SHA256与密钥进行强关联,使整个系统达到一图一密的加密效果,提高了明密文间的雪崩效应,增强了算法抗选择明密文攻击的能力.     

基于超混沌和Gyrator域相位信息复用的光学多图像认证方法

针对光学多图像认证方法中,多路复用图像中的串扰噪声,以及不同认证级别下的信息安全问题,提出了一种基于超混沌振幅型掩模和Gyrator变换域下相位信息复用的光学多图像认证方法。利用分数阶超混沌Rabinovich系统构造超混沌随机振幅掩模;基于改进的Gerchberg-Saxton算法对原始图像进行低级或高级编码,利用超混沌掩模作为振幅约束,迭代获得目标图像,并将得到的N个目标图像编码成复合图像;再次通过Gerchberg-Saxton迭代将复合图像转化为两个便于传输的纯相位掩模。实验结果表明:在认证过程中,不同安全级别的用户拥有各自的认证密钥,低级认证过程中可以通过检索图像与原始图像的非线性相关峰值,判断认证图像的正确性,而高级认证过程中则可以获得与原始图像相似度较高的认证图像,峰值信噪比和相关系数分别可达25.2817 dB和0.9844。所提方法对遮挡攻击和噪声攻击具有良好的稳健性,为多幅图像在不同级别下的光学认证提供了新的思路。     

基于混沌的改进双随机相位编码图像加密算法

针对菲涅耳域双随机相位编码提出的一种改进图像加密系统。该系统通过预先将原图像编码为相位信息克服了原算法对第一块相位模板和第一次衍射距离不敏感的缺陷。在双随机相位编码模块后基于复值图像振幅及相位替代的再次加密,使得加密图像像素值分布更为均匀。另外,改进算法引入三种不同的混沌系统来生成所需要的随机模板,借助于混沌系统的非线性性、初值敏感性,加密系统在减小密钥体积的同时增大了密钥空间、增加了系统的复杂性。仿真实验对算法进行了有效性分析、统计分析以及密钥敏感性测试,结果表明改进的算法有效提升了原算法的安全性。     

结合计算全息与混沌的彩色图像加密方法

针对现有彩色图像光学加密方法存在解密结果失真的问题,提出一种结合混沌运算与菲涅耳衍射全息的彩色图像单通道加密新方法.首次加密操作利用菲涅耳衍射将彩色图像RGB通道分量转换成一幅实值计算全息图;第二次加密操作是利用改造的Logistic混沌系统对计算全息图像素进行置换与扩散.结果 表明,本文方法除传统混沌系统密钥以外,菲涅耳衍射距离、参考光波长和入射角方向余弦作为关键密钥均可以增大密钥空间(约为10249),而且具有较小的密钥体积;解密图像的保真度高且相邻像素相关性、信息熵、像素数改变率和归一化改变强度等评价指标均接近理想值;密文图像的直方图平坦,灰度分布均匀,完全隐藏了原始彩色图像的灰度和色彩信息.     

Fractional Fourier plane image encryption technique using radial hilbert-, and Jigsaw transform

A new method for image encryption using integral order radial Hilbert transform (RHT) filter in the fractional Fourier transform (FRT) domain has been proposed. The technique is implemented using the popular double random phase encoding method in the fractional Fourier domain. The random phase masks (RPMs), integral orders of the RHT, fractional orders of FRT, and indices of the Jigsaw transform (JT) have been used as keys for encryption and decryption. Simulation results have been presented and the schematic representation for optical implementation has been proposed. The mean-square-error and signal-to-noise ratio between the decrypted image and the input image have been calculated for the correct as well as incorrect orders of the RHT. Effect of occlusion and noise on the performance of the proposed scheme has also been studied. The robustness of the technique has been verified against attack using partial windows of the correct random phase masks. Similar investigations have also been carried out for the chosen-, and the known-plain-text attacks.     

Fractional Fourier transform based image multiplexing and encryption technique for four-color images using input images as keys

A digital technique for multiplexing and encryption of four RGB images has been proposed using the fractional Fourier transform (FRT). The four input RGB images are first converted into their indexed image formats and subsequently multiplexed into a single image through elementary mathematical steps prior to the encryption. The encryption algorithm uses two random phase masks in the input- and the FRT domain, respectively. These random phase masks are especially designed using the input images. As the encryption is carried out through a single channel, the technique is more compact and faster as compared to the multichannel techniques. Different fractional orders, the random masks in input-, and FRT domain are the keys for decryption as well as de-multiplexing. The algorithms to implement the proposed multiplexing-, and encryption scheme are discussed, and results of digital simulation are presented. Simulation results show that the technique is free from cross-talk. The performance of the proposed technique has also been analyzed against occlusion, noise, and attacks using partial windows of the correct random phase keys. The robustness of the technique against known-, and chosen plain-text attacks has also been explained.     

Logarithms-based RGB image encryption in the fractional Fourier domain: A non-linear approach

We propose a non-linear image encryption scheme for RGB images, using natural logarithms and fractional Fourier transform (FRT). The RGB image is first segregated into the component color channels and each of these components is hidden inside a random mask (RM) using base changing rule of logarithms. Subsequently, these channels are encrypted independently using random phase masks (RPMs) and the FRT. The fractional orders of the FRT, input random masks and random phase masks used in each channel serve as the keys for encryption and decryption. The algorithms to implement the proposed scheme are discussed, and results of digital simulation are presented. The robustness of the technique is analyzed against the variation in fractional orders of the FRT, change of RMs and RPMs, and occlusion of the encrypted data, respectively. Performance of the scheme has also been studied against the attacks using noise and partial windows of the correct RPMs. The proposed technique is shown to perform better against some attacks in comparison to the conventional linear methods.     

Double image encryption based on linear blend operation and random phase encoding in fractional Fourier domain

A novel method for double image encryption is proposed by using linear blend operation and double-random phase encoding (DRPE) in the fractional Fourier domain. In the linear blend operation, a random orthogonal matrix is defined to linearly recombined pixel values of two original images. The resultant blended images are employed to constitute a complex-valued image, which is encrypted into an encrypted image with stationary white distribution by the DRPE in the fractional Fourier domain. The primitive images can be exactly recovered by applying correct keys with fractional orders, random phase masks and random angle function that is used in linear blend operation. Numerical simulations demonstrate that the proposed scheme has considerably high security level and certain robustness against data loss and noise disturbance.     

Color image encryption and decryption for twin images in fractional Fourier domain

We propose a method for the encryption of twin color images using fractional Fourier transform (FRT). The color images to be encrypted are converted into the indexed image formats before being processed through twin image encryption algorithm based on the FRT. The proposed algorithm uses one random code in the image domain and one random phase code in the FRT domain to perform double image encryption. The conversion of both the input RGB images into their indexed formats facilitates single-channel processing for each image, and is more compact and robust as compared to multichannel techniques. Different fractional orders, the random masks in image- and FRT domain are the keys to enhance the security of the proposed system. The algorithms to implement the proposed encryption and decryption schemes are discussed, and results of digital simulation are presented. We examine sensitivity of the proposed scheme against the use of unauthorized keys (e.g. incorrect fractional orders, incorrect random phase mask etc.). Robustness of the method against occlusion and noise has also been discussed.     

Linear exchanging operation and random phase encoding in gyrator transform domain for double image encryption

We present an optical method for double image encryption by using linear exchanging operation and double random phase encoding (DRPE) in the gyrator transform (GT) domain. In the linear exchanging operation, two primitive images are linearly recombined via a random orthogonal transform matrix. The resultant blended images are employed to constitute a complex-valued image, which is then encoded into a noise-like encrypted image by a DRPE structure in the GT domain. One can recover the primitive images exactly with all decryption keys correctly applied, including the transform orders, the random phase masks and random angle function used for linear exchanging operation. Computer simulations have been given to demonstrate that the proposed scheme eliminates the difference in key spaces between the phase-based image and the amplitude-based image encountered in the previous schemes. Moreover, our scheme has considerably high security level and certain robustness against data loss and noise disturbance.     

基于干涉原理的虚拟光学加密系统

提出了一种虚拟光学加密系统。该光学加密系统采用了同轴全息技术的基本架构,将被加密图像作为被记录物体,而在参考光波及干涉场光路中分别引入两个独立的随机相位板,全息面上的输出即为加密结果,这两个随机相位板即为加密及解密所用密钥。理论分析表明,在恰当设置物光波与参考光波衍射场比例的情况下,任意一灰度图像均可被加密为平稳的复随机白噪声,可以抵御盲反卷积攻击。采用计算机模拟,证实了该系统的加密效果及对抗暴力攻击的能力。研究了解密时附加参数及噪音攻击对解密结果的影响,结果表明本系统抗噪音攻击能力一般,但对附加参数有极高的敏感性。     

Phase image encryption of colored images using double random phase encoding technique in HSV color space

A double random phase encoding based digital phase encryption technique for colored images is proposed in the Fourier domain. The RGB input image is brought to HSV color space and then converted into phase, prior to the encryption. In the decryption process the HSV image is and converted back to the RGB format. The random phase codes used during encryption are prepared by stacking three two-dimensional random phase masks. These random phase codes serve as keys for encryption and decryption. The proposed technique carries all the advantages of phase encryption and is supposedly three-dimensional in nature. Robustness of the technique is analyzed against the variations in random phase codes and shuffling of the random phase masks of a given phase code. Performance of the scheme is also verified against occlusion of Fourier plane random phase code as well as the encrypted image. Effects of noise attacks and attacks using partial windows of correct random phase codes have also been checked. Digital simulations are presented to support the idea.     

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.     

Digital image synthesis and multiple-image encryption based on parameter multiplexing and phase-shifting interferometry

A novel digital image synthesis and multiple-image encryption technique based on parameter multiplexing and phase-shifting interferometry by discrete Fresnel transform is proposed. Both the image synthesis and the multiple-image encryption can be realized with the same system arrangement and similar principles, while the former is achieved by using different sets of parameters (wavelength and distance) and the same set of random phase masks, and the latter with different sets of random phase masks. The feasibility of this method and its robustness against occlusion and additional noise attacks are verified by computer simulations. The encryption capacity of the system is analyzed in term of the correlation coefficient. This technique is simple with a lensless setup, highly secure, and particularly suitable for the image transmission via Internet.