基于多分数阶混沌系统的彩色图像加密算法

为了实现对彩色图像信息的有效保护，提出一种像素置乱及密文交错扩散技术相结合的加密算法。首先对3个分数阶混沌系统产生的混沌序列进行优化改进，得到两组不同的性能优良的混沌密钥序列，并将RGB彩色图像转换为由基色分量组成的灰度图像；然后，利用一组改进的混沌密钥序列对该灰度图像的像素位置进行置乱；最后，利用另一组改进的混沌密钥序列对置乱图像进行2轮基色分量之间的密文交错扩散操作，得到加密图像。仿真实验表明，该算法具有足够大的密钥空间，高度的密钥敏感性，较好的像素分布特性，且在抵抗唯密文攻击、差分攻击、选择明文攻击及统计攻击方面都具有良好的性能，可以广泛地应用于多媒体数据的保密通信中。

A Color Image Encryption Algorithm Based on Multiple Fractional-order Chaotic Systems

In order to achieve effective protection of color image information, an encryption algorithm with the combination of pixel scrambling and ciphertext cross-diffusion technology is proposed. Firstly, the chaotic sequences generated by three fractionalorder chaotic systems are modified to obtain two groups of chaotic key sequences with good property, and the RGB color image is converted into a gray-scale image which is composed by primary color components. Secondly, the pixels＇ positions of the grayscale image are scrambled by means of one group of improved chaotic key sequences. Thirdly, by using another group of improved chaotic key sequences, the study modifies the pixels＇ values of the scrambled image with two rounds of eiphertext cross-diffusion operations between the primary color components and gets the cipher image. Simulation shows that, this algorithm is of a sufficiently large key space, highly sensitive keys, better pixel distribution characteristics, and a good performance against ciphertextonly attack, differential attack, chosen plaintext attack and statistical attack. This can be widely used in secure communication of multimedia data.