基于改进Lorenz混沌系统的图像加密新算法

A new image encryption algorithm based on improved Lorenz chaotic system

为了提高图像加密算法的加密安全性和抗攻击能力,提出一种基于改进Lorenz混沌系统的图像加密新算法。首先,将Lorenz系统中的1个非线性项用指数函数项与单变量2次平方项的和替代;然后,分析该改进Lorenz系统的动力学特性,证实其混沌特性;最后,利用该混沌映射生成分别用于置乱加密和替代加密的2组密钥序列,进行图像的加密和解密操作:在置乱加密阶段,将图像像素灰度进行升序排列,并与置乱加密密钥序列结合实现像素位置置乱;在替代加密阶段,采用密文反馈的加密方式修改像素灰度。研究结果表明:该算法能有效抵御选择明文攻击,密文图像像素具有类随机均匀分布特性,且相邻像素具有零相关特性,拥有192 bit的密钥空间且对密钥非常敏感。

In order to improve the security and anti-attack ability of image encryption algorithm,a new image encryption algorithm based on improved Lorenz chaotic system was proposed.Firstly,a nonlinear term in the Lorenz system was replaced by an exponential function term and a two-square term of a single variable.Then,the dynamic characteristics of the improved Lorenz system were analyzed,which proved the chaotic characteristics of the system.Finally,the chaotic map was used to generate two groups of key sequences which were used for scrambling encryption and alternative encryption.In the scrambling encryption stage,the image pixel gray values were arranged in ascending order,and were combined with encryption key sequence to achieve pixel position scrambling.In the replacement encryption stage,the gray values of the pixels were modified by the way of cipher text feedback.The results show that the algorithm can effectively resist chosen plaintext attack,and the encrypted image has random-like distribution behavior of grey values and the adjacent pixels have zero correlation.The algorithm has192bit key spaces and it is very sensitive to the key.