中文说明：
基于MATLAB的图像加密解密系统含GUI界面。
一、课题名称 基于MATLAB的Arnold和混沌图像加密解密系统
二、课题介绍 该课题采用Arnold和混沌两种算法对彩色图像进行加密、解密操作。同时配备一个GUI可视化界面。 Arnold变换，俗称猫脸变换.。基本思想是对图像矩阵进行有限次的初等矩阵变换，可以有效地打乱输入明文的次序，进而有效地掩盖明文信息，达到加密的目的。设像素的坐标x , y S = {0, 1, 2, „, N-1},则Arnold变换为： 公式中的N表示数字图像的阶数，（x,y）为像素点的坐标。 将二维Arnold变换应用在图像f（x,y）上，可以通过像素坐标的改变而改变原始图像灰度值的布局。原始图像可以看作一个矩阵，经过Arnold变换后的图像会变的“混乱不堪”，由于Arnold变换的周期性，继续使用Arnold变换，可以重现图像。利用Arnold变换的这种特性，可实现图像的加密与解密。n维Arnold变换同二维Arnold变换一样具有周期性，继续使用Arnold变换，也可以重现原始图像。利用n维Arnold变换对图像的相空间进行置乱，也能实现图像的加密。 混沌算法，混沌系统由于其很好地反映了随机性特征 ,近年来在图像加密领域被学者们广泛地研究。但加密技术仍面临许多难题 ,传统的混沌图像加密算法难以抵御 已知明文攻击 ,差分分析的抵御能力是衡量加密算法安全性的重要指标之一。为了解决加密算法抵御已知明文攻击的能力 ,国内外的研究人员在此基础上提出了改进的图像加密算法。其中经典的方法包括采用超混沌或复合混沌系统完成彩色图像的加密 ,缺陷是时间复杂度较高。采用分层分块的图像加密算法可以有效提高加密速度 ,但是对图像尺寸具有严格的局限性。针对上述情况 ,本文提 出了一种基于混沌 的像素混淆和扩散的加密算法 ,根据分组密码具有混淆和扩散两个机制 ,结合混沌动力系统特有的优点 ,该方案简单、快速并且对密钥敏感,不仅有效抵抗统计分析 ,而且对已知明文攻击也具有较好的抵御能力。
English Description：
The image encryption and decryption system based on MATLAB includes GUI interface Arnold and chaotic image encryption and decryption system based on MATLAB & nbsp Second, the subject introduces that Arnold and chaos algorithms are used to encrypt and decrypt the color image. At the same time, it is equipped with a GUI visual interface. Arnold transform, commonly known as cat face transform. The basic idea is to transform the image matrix to a finite number of elementary matrix, which can effectively disrupt the order of input plaintext, and then effectively cover up the plaintext information to achieve the purpose of encryption. Let x, y, s = {0, 1, 2, n-1}, then Arnold transform is: N in the formula represents the order of the digital image, and (x, y) is the coordinate of the pixel& nbsp; Applying the two-dimensional Arnold transform to the image f (x, y), the layout of the gray value of the original image can be changed by changing the pixel coordinates. The original image can be regarded as a matrix, and the image after Arnold transformation will become "chaotic". Because of the periodicity of Arnold transformation, the image can be reproduced by Using Arnold transformation. Using this characteristic of Arnold transform, image encryption and decryption can be realized. The n-dimensional Arnold transform has the same periodicity as the two-dimensional Arnold transform. If we continue to use the Arnold transform, we can also reproduce the original image. Using the n-dimensional Arnold transform to scramble the phase space of the image can also realize the image encryption. In recent years, chaotic algorithm and chaotic system have been widely studied in the field of image encryption because they reflect the randomness. But encryption technology still faces many problems. The traditional chaotic image encryption algorithm is difficult to resist the known plaintext attack. The resistance ability of differential analysis is one of the important indexes to measure the security of encryption algorithm. In order to solve the ability of encryption algorithm to resist known plaintext attacks, researchers at home and abroad proposed an improved image encryption algorithm. Among them, the classical methods include the use of Hyperchaotic or compound chaotic system to complete the color image encryption, but the defect is the high time complexity. The image encryption algorithm based on layer and block can effectively improve the encryption speed, but it has strict limitations on image size. In view of the above situation, this paper proposes a pixel confusion and diffusion encryption algorithm based on chaos. According to the two mechanisms of confusion and diffusion of block cipher, combined with the unique advantages of chaotic dynamic system, the scheme is simple, fast and sensitive to key. It not only effectively resists statistical analysis, but also has good resistance to known plaintext attacks