基于超混沌系统与DNA编码的图像加密研究

Research on Image Encryption Based on Hyper-Chaotic System and DNA Encoding

针对图像加密方案中密钥敏感性弱、相邻位置像元相关性强等问题,提出一种基于超混沌系统置乱、扩散及DNA编码的彩色图像加密算法。首先,将原图像经R、G、B通道分层得到的3个二维灰度图像矩阵进行补零操作后划分为16个子块;然后,对各模块进行扩散得到一个随机矩阵,利用多混沌系统产生的4条混沌序列值确定DNA编码与运算规则,分别对补零后的矩阵和随机矩阵进行DNA运算。为获得更好的扩散效果,在对两个矩阵子块进行DNA运算及解码操作后,由Logistic混沌映射迭代的两条混沌序列对其进行行列位置置乱,重新组合图像子块得到彩色加密图像。仿真表明,改进后的加密算法密钥空间达到10128数量级,在图像水平、垂直及对角方向上相关性系数平均达到-0.0043,计算得到的UACI值为33.3687%,NPCR值为99.6956%,对降低图像相邻位置像素数值相关性及各种攻击的能力更强。

A color image encryption algorithm based on hyperchaotic system scrambling,diffusion,and DNA encoding is proposed to address the issues of weak key sensitivity and strong correlation between adjacent pixels in image encryption schemes.Firstly,the original image is di⁃vided into 16 sub blocks by performing zero padding operations on the three two-dimensional grayscale image matrices obtained by layering the R,G,and B channels;Then,each module is diffused to obtain a random matrix,and the DNA encoding and operation rules are deter⁃mined using the four chaotic sequence values generated by the multi chaotic system.DNA operations are performed on the zero filled matrix and the random matrix,respectively.To achieve better diffusion effect,after DNA operation and decoding operation on the two matrix sub blocks,the two chaotic sequences iterated by Logistic chaotic mapping are scrambled in row and column positions,and the image sub blocks are recombined to obtain a color encrypted image.Simulation shows that the improved encryption algorithm achieves a key space of 10128 orders of magnitude,with an average correlation coefficient of-0.0043 in the horizontal,vertical,and diagonal directions of the image.The calculat⁃ed UACI value is 33.3687%,and the NPCR value is 99.6956%.It has a stronger ability to reduce the correlation between adjacent pixel val⁃ues in the image and various attacks.