基于参数转换混沌耦合系统及其一维、二维变换规则的图像加密算法

The Study on Image Encryption Algorithm Based on the Parametric Switching Chaotic System and Its 1D,2D Transformation Rules

1D混沌映射具有结构简单以及高的计算效率等独特优点,但其输出序列的值域差别大,易出现局部单调现象;且其安全性较低。为了继承一维混沌映射的优点;解决当前加密系统普遍难以同时兼顾高安全性与高计算效率等难题,设计了一维参数转换混沌耦合系统和一个混沌序列优化机制,并定义了该耦合系统对应的1D、2D变换规则,提出了基于参数转换混沌系统及其1D、2D变换规则的图像加密算法。首先迭代一维参数转换混沌耦合系统,得到混沌序列;然后利用1D变换规则将混沌序列转换成整数序列;并将该整数序列分割成两个子序列,用其中的一个子序列对图像进行替代;再用另外一个子序列根据2D变换规则对替代图像进行置乱;最后根据序列优化机制对混沌序列进行优化后所得到的新序列来加密图像。MATLAB仿真结果显示:与其他算法相比,加密质量更好、算法高度安全、密钥空间更大。

1D chaotic map has theses unique advantages such as high computation efficiency and simple struc ture, but the range difference between its output sequences is big, and easily appear the phenomenon of local mo notony, and its security was very low. In order to inherit the advantages of onedimensional chaotic maps, and overcome the shortage of not simultaneously both having high security and high computation efficiency, the 1 D para metric switching chaotic coupled system based on several 1D chaotic maps and optimization mechanism of chaotic sequence were designed, as well as defending the 1 D, 2D transformation rules corresponding to the coupled system to propose the image encryption algorithm based on the parametric switching chaotic system and its 1D ,2D transfor mation rules. The chaotic sequence was got by iteration the 1 D parametric switching chaotic coupled system; then the chaotic sequence was transformed into the integer sequence by the 1 D transformation rule; the integer sequence was divided into two subsequence, one for substituted the image ; and the substitution image was permutated by an other subsequence under the condition of 2D transformation rule; the new sequence obtained by optimizing the cha otic sequence according to the optimization mechanism of chaotic sequence to encryption permutation image. The results of MATLAB simulation were showed that compared with other encryption algorithms, the encryption algo rithm had better encryption quality and higher security; and the key space was huge.