基于相邻像素间比特置乱的图像加密算法

针对现有单一像素点间比特置乱的图像加密算法存在对所用混沌序列不敏感,以及抵御选择明(密)文攻击弱的问题,提出一种相邻像素点间比特置乱的方式,用Kent、Logistic混沌映射对明文图像进行像素位置全局置乱、相邻像素比特置乱以及扩散操作。相邻两像素点置乱充分利用像素点全局置乱后的图像相关性极低这一特性,解决单一像素点进行比特置乱时对所用的混沌序列不敏感问题。采用正反双向不同混沌序列扩散结合明文的哈希值SHA-256,有效抵御选择明(密)文攻击。实验结果表明,该算法对明文、密钥敏感性强,密文分布均匀、相邻像素相关性低,能较好抵御统计分析、差分攻击和选择明(密)文攻击。

Image encryption algorithm based on scrambled bits between adjacent pixels

The existing image encryption algorithms are insensitive to the chaotic sequences used,and the ability to resist chosen plaintext(ciphertext)attacks is weak.A method of bit scrambling between adjacent pixels was proposed.Kent and Logistic chaotic maps were used to perform global scrambling of pixel positions,scrambling of adjacent pixel bits and diffusing operations on plaintext images.The scrambling of two adjacent pixels made full use of the feature that the global scrambling of pixels has very low image relevance,so as to solve the problem that a single pixel is not sensitive to the chaotic sequence used in the bit scrambling.The positive and negative bidirectional diffusion of different chaotic sequences and the hash value SHA-256 of the plaintext were used to resist the chosen ciphertext attack effectively.Experimental results show that the proposed algorithm has strong sensitivity to plaintext and key,uniform ciphertext distribution and low correlation between adjacent pixels,which can better resist statistical analysis,differential attack and selective attack.