改进的置乱扩散同步实现的图像加密算法

为改善图像加密算法对初始密钥的依赖性,提高算法的抗穷举攻击、抗统计分析攻击和抗差分攻击等性能,提出了一种改进的置乱扩散同步实现的图像加密算法,用于加密矩形灰度图像.先按照某种扫描模式重排图像像素,然后选用成对的Logistic映射产生的混沌序列作用于明文图像;最后,采用基于Chebyshev-Logistic混沌序列控制的一种明密文双向结合的扩散方式,对置乱后的图像进行扩散.为评价该算法的性能,做了密钥空间分析,统计直方图分析,相邻像素相关性分析,信息熵测试,以及扩散性测试等大量的仿真实验.仿真实验表明,该算法扩展了密钥空间,对密钥初始值有超强的依赖性,提高了密文图像的抗穷举攻击、统计分析攻击和差分攻击的能力.

An improved image encryption algorithm based on the synchronization of permutation and diffusion

To reduce the dependency of image encryption algorithm on the initial keys and to improve its abilities in resistance to exhaustive attack, statistical attack and differential attack, a modified image encryption algorithm used for encrypting the rectangular grayscale of object was presented, which was obtained by permutation and diffusion synchronously. Firstly, rearranged the image pixels through scanning. A chaotic sequence generated from double logistic map was operated on the plaintext image. Finally, diffuse the scrambled image by a method based on double-direction combination between plaintext and ciphertext that was controlled by Chebyshev-Logistic chaotic sequence. Analysis including key space, statistical histogram, correlation of adjacent pixels, information entropy test, and diffusion test was made to evaluate the performance of this algorithm, simulation results show that such algorithm is very dependent on the initial-values, it extends the key space effectively, and improves the image''s ability of encryption algorithm in resistance to exhaustive attack, statistical attack and differential attack effectively.