一种基于Arnold变换的数字图像加密算法

提出了一种基于Arnold变换的均匀数字图像加密算法。将传统的Arnold变换进行改进,加入两个参数a,b,并利用Logistic映射产生参数序列。将数字图像分块,对每个图像块分别进行参数不同的Arnold变换,由此实现对图像的位置置乱。另外将Arnold变换推广至多维,用于图像的灰度置乱,从而构造一个位置置乱和灰度置乱相结合的图像加密算法。实验仿真结果表明该算法能够取得很好的加密效果,且具有密钥空间大,密钥敏感性强,以及能够抵御统计和已知明文攻击等优点。基本满足图像加密的有效性和安全性要求。     

基于组合混沌和位运算的图像加密算法

为了有效改进图像加密效果及其安全性,在对基于混沌系统及位运算的图像加密算法进行研究的基础上,提出基于组合混沌和位运算的图像加密算法,算法先对灰度图像进行位平面分解,考虑到图像的高四位含有较大的信息量,对高四位分别进行置乱变换,再与低四位构成一个整体进行置乱变换,然后组合置乱后的位平面,并与二值矩阵进行异或运算得到密文图像。实验结果表明,与像素位置置换算法和二维数据加密算法比较,改进算法具有更好的加密效率,密钥空间接近2192,具有较好的安全性,且能较好地抵御椒盐噪声和高斯噪声攻击,有效恢复出原始图像。     

基于混沌映射的图像快速加密改进算法

针对当前的三维混沌映射加密算法存在安全性不高,加密速度慢以及密钥空间小等不足,提出了一种新的三维混沌映射图像加密算法;首先利用快速置乱方法置乱初始图像,以改变像素位置;利用三维Chen系统结合像素值变换函数所生成初始外部密钥迭代三维混沌映射,得到一个序列,由此根据混淆机制对置乱图像像素值进行混淆;改变外部密钥,再迭代计算三维混沌映射,得到三元一维伪随机数组,借助密钥流机制量化该数组,得到新数组,由此根据扩散机制对混淆后的像素进行扩散处理;采用酷睿3.5 GHz双核CPU的PC机和MATLAB仿真平台,输入256×256的明文图像实验,置乱100次所用时间为78.67 s,在灰度平面内其相关性约为-0.001 652,表明该算法高度安全,密钥空间巨大,加密速度快,用于图像快速加密是可行、有效的。     

基于Logistic均匀分布图像置乱方法

针对许多基于Logistic图像置乱方法的设计只注重置乱规则和方法,没能很好地给出设计原理这一现象,文章遵循从坚实的数学理论到实际应用这一科学过程,给出了一个全新的具有坚实理论基础的基于Logistic图像置乱算法.依据混沌初值敏感性,密钥空间大这一特性,从混沌映射Logistic着手,结合概率相关理论,设计了基于Logistic映射(0,1)区间上的均匀分布随机变量产生算法,利用这一均匀分布变量生成基于位置互换的随机排列.为了度量该随机排列的置乱强度,设计了置乱强度测试算法.最后,利用这一基于Logistic均匀分布的随机排列驱动图像生成置乱图像.比较Baker算法、Ye算法和Yoon算法,结果显示,文章建议的Logistic图像置乱算法具有很大的密钥空间,很强的密钥敏感性,很强的使结构性数据相关性消失的性能,进而能够增加熵值,很好的抗攻击能力,可以有效地满足图像置乱需求. 关键词： 图像置乱 混沌序列 随机置乱 比特置乱     

一种双重变换的二维图像加密算法

提出了一种改进的双重加密算法,利用新构造的位置置乱方法将二维矩阵中行和列映射到一维向量中,然后采用Logistic映射产生一组伪随机序列,将伪随机序列由小到大进行排序,对排序后的位置以集合序列的形式记录下来,形成密钥流;最后对一维向量按照密钥流形成的索引值进行重新排列,重排后的一维向量转换为与原始图像矩阵大小相同即得到加密图像。实验结果表明,该算法具有密钥空间大,加密后直方图分布具有白噪声的特性,提高了图像传输的安全性。     

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。     

三维可逆混沌映射的图像加密算法

提出了一种三维可逆混沌映射图像加密算法。基于Line map二维混沌可逆映射,推导了该三维可逆映射的数学表达式。将灰度图像用一个三维矩阵数据描述,并按照所提出的算法将其组成一个二维的二进制图像。首先对此图像应用Line map二维混沌可逆映射进行像素置乱处理,然后再将置乱后的二进制图像还原成十进制的灰度图像,这样就得到了加密后的图像。所提出的方法可以通过一次三维可逆混沌映射同时实现图像加密的两个步骤,即像素置乱和像素混淆。仿真实验结果表明了该算法的有效性,且加密速度快、安全性高、简单易行。     

基于联合变换相关和相移干涉的图像加密

提出了一种在联合变换相关器结构中引入三步相移干涉和二元置乱技术的图像加密方法.用纯相位空间光调制器同时调制原始图像和两个随机相位掩模,利用三步相移技术分别将图像信息和主密钥加密为全息图,并用CCD在输出面上接收,再利用二元置乱技术置乱图像信息的全息图.在获得置乱密钥和附加密钥的情况下,可以通过一定的算法快速、清晰的重建原始图像.用计算机仿真验证了它的可行性和有效性.     

基于像素置乱技术的多重双随机相位加密法

提出一种基于像素置乱技术的多重双随机相位加密法,对该加密法中像素置乱操作的原理进行了阐述,并且提出在光学上实现像素置乱操作和解置乱操作的途径.在计算机上模拟实现了该加密法,并且得到很好的加密解密结果.仿真结果证实仅用部分加密图像来解密也能够得到原图像,并且得到随着待解密的加密图像像素的增加,解密图像的信号能量、噪声以及信噪比的变化曲线.最后分析比较了该加密法与双随机相位加密法,得到该加密法与双随机相位加密法相比具有更高的保密性,而且解密图像的信噪比也不会因为引入像素置乱操作而降低.     

基于双混沌置乱和扩频调制的彩色图像盲水印算法

提出了一种新的适应彩色图像的盲水印算法,先对宿主图像的绿色分量以8×8像素分块进行离散余弦变换(DCT)变换,用logistic映射生成两个混沌序列,然后用混沌序列置乱加密二值水印图像,并用两个互不相关的伪随机序列扩频调制水印,最后将调制好的水印嵌入到DCT变换域的中频子带系数上,进行分块DCT反变换得到水印化图像.提取水印时,通过比较两个伪随机序列和水印化图像的相关性大小来提取水印,不需要原始图像的参与,为盲提取水印算法.实验结果证明本文算法能有效地抵抗JPEG压缩、加噪、剪切等常见攻击,绿色分量嵌入水印比红色和蓝色分量嵌入水印能更好地抵抗JPEG压缩的攻击.     

Double image encryption by using Arnold transform and discrete fractional angular transform

Based on Arnold transform and discrete fractional angular transform, a double image encryption algorithm is designed. Two original images are regarded as the amplitude and phase of a complex function. Arnold transform is introduced for scrambling the pixels at a local area of the complex function. Subsequently the changed complex function is converted by discrete fractional angular transform. The operations mentioned will be performed many times. The amplitude of final output complex function is the encrypted image and its phase is regarded as the key of encryption algorithm. The parameters of the two transforms serve as the additional keys for enhancing the security. Some numerical simulations have been done to validate the performance of this encryption scheme.     

A Novel Image Encryption Algorithm Based on Improved Arnold Transform and Chaotic Pulse-Coupled Neural Network

Information security has become a focal topic in the information and digital age. How to realize secure transmission and the secure storage of image data is a major research focus of information security. Aiming at this hot topic, in order to improve the security of image data transmission, this paper proposes an image encryption algorithm based on improved Arnold transform and a chaotic pulse-coupled neural network. Firstly, the oscillatory reset voltage is introduced into the uncoupled impulse neural network, which makes the uncoupled impulse neural network exhibit chaotic characteristics. The chaotic sequence is generated by multiple iterations of the chaotic pulse-coupled neural network, and then the image is pre-encrypted by XOR operation with the generated chaotic sequence. Secondly, using the improved Arnold transform, the pre-encrypted image is scrambled to further improve the scrambling degree and encryption effect of the pre-encrypted image so as to obtain the final ciphertext image. Finally, the security analysis and experimental simulation of the encrypted image are carried out. The results of quantitative evaluation show that the proposed algorithm has a better encryption effect than the partial encryption algorithm. The algorithm is highly sensitive to keys and plaintexts, has a large key space, and can effectively resist differential attacks and attacks such as noise and clipping.     

Double-image encryption by using chaos-based local pixel scrambling technique and gyrator transform

A novel double-image encryption algorithm is proposed by using chaos-based local pixel scrambling technique and gyrator transform. Two original images are first regarded as the amplitude and phase of a complex function. Arnold transform is used to scramble pixels at a local area of the complex function, where the position of the scrambled area and the Arnold transform frequency are generated by the standard map and logistic map respectively. Then the changed complex function is converted by gyrator transform. The two operations mentioned will be implemented iteratively. The system parameters in local pixel scrambling and gyrator transform serve as the keys of this encryption algorithm. Numerical simulation has been performed to test the validity and the security of the proposed encryption algorithm.     

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.     

Quantum Multi-Image Encryption Based on Iteration Arnold Transform with Parameters and Image Correlation Decomposition

A novel quantum multi-image encryption algorithm based on iteration Arnold transform with parameters and image correlation decomposition is proposed, and a quantum realization of the iteration Arnold transform with parameters is designed. The corresponding low frequency images are obtained by performing 2-D discrete wavelet transform on each image respectively, and then the corresponding low frequency images are spliced randomly to one image. The new image is scrambled by the iteration Arnold transform with parameters, and the gray-level information of the scrambled image is encoded by quantum image correlation decomposition. For the encryption algorithm, the keys are iterative times, added parameters, classical binary and orthonormal basis states. The key space, the security and the computational complexity are analyzed, and all of the analyses show that the proposed encryption algorithm could encrypt multiple images simultaneously with lower computational complexity compared with its classical counterparts.     

离散分数阶随机变换与加权直方图交叉置乱的双图像加密算法

为了实现对两幅图像进行同步加密,降低传输负载并提高密文的抗明文攻击能力,提出了离散分数阶随机变换与加权像素混沌置乱的双图像加密算法。将2个分阶参数引入到Tent映射中,设计了新的Tent映射;根据明文像素值,构建加权像素直方图模型,联合位外部密钥,生成改进的Tent映射的初值;再利用初值对分数阶Tent映射进行迭代,输出2组随机序列,对2幅明文进行位置交叉混淆,获取2个置乱密文;基于DWT(discrete wavelet transform)技术,对2个置乱密文进行稀疏表示;根据混沌序列,定义随机循环矩阵,联合稀疏表示,获取2个置乱密文对应的测量矩阵。根据随机掩码与调制相位掩码,建立数据融合模型,将2个测量矩阵组合为复合矩阵;基于离散分数阶随机变换,对复合图像进行扩散,获取密文。测试数据显示:与已有的多图像加密方案相比,该算法的抗明文攻击能力与用户响应值更理想,密文的NPCR、UACI值分别达到了99.83%、34.57%。该算法具有较高的加密安全性,能够有效抵御网络中的外来攻击,确保图像安全传输。     

Novel color image encryption algorithm based on the reality preserving fractional Mellin transform

A nonlinear color image encryption algorithm based on reality preserving fractional Mellin transform (RPFrMT) is proposed. So far as image encryption is concerned, RPFrMT has two fascinating advantages: (1) the real-valued output of the transform ensures that the ciphertext is real which is convenient for display, transmission and storage; (2) as a nonlinear transform, RPFrMT gets rid of the potential insecurity which exists in the conventional linear encryption schemes. The original color image is first transformed from RGB color space to R′G′B′ color space by rotating the color cube. The three components of the output are then transformed by RPFrMT of different fractional orders. To further enhance the security of the encryption system, the result of the former step is scrambled by three dimensional scrambling. Numerical simulations demonstrate that the proposed algorithm is feasible, secure, sensitive to keys and robust to noise attack and occlusion. The proposed color image encryption can also be applied to encrypt three gray images by transforming the gray images into three color components of a specially constructed color image.     

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。     

基于混沌与位平面的图像置乱方法

根据混沌序列良好的随机性及灰度图像可分成若干位平面二值图的特点,提出了将混沌二值序列与位平面图像异或运算进行置乱,将置乱后的位平面图重新组合成灰度图,以此达到灰度图像置乱的效果。仿真结果表明,基于混沌与位平面的图像置乱方法可有效地使图像灰度值均匀化。