基于改进cat映射与混沌系统的彩色图像快速加密算法*

针对已有基于混沌系统的图像加密算法计算复杂度较高的问题，基于改进cat映射提出一种计算复杂度较低、易于实现的彩色图像加密算法。本算法包括置乱与扩散两层，置乱层采用比特置乱代替传统的字节置乱，彻底打乱图像各像素的位置，并且对传统二维cat映射进行改进，大幅度地提高了计算效率，采用均匀的混沌伪随机产生器动态地改变加解密过程每轮的控制参数，提高了加密系统的安全性；扩散层则采用比特矩阵方法将每块扩散处理。基于真实图像的实验结果表明，本算法可抵御不同类型的攻击，计算效率较高。

Improved cat map and chaotic system based fast color image encryption algorithm

Aimed at the problem that the existing chaotic system based image encryption algorithms has high computational complexity, an improved cat map based color image encryption algorithm with low computational complexity and easily to implement is proposed. The proposed method contains two layers, in permulation layer bit based permulation is used to replace the traditional byte based permulation to disrupt the positions of the pixels completely, and the traditional 2 dimensional cat map is improved, so that the computational efficiency is improved drastically, uniform chaotic fake random sequence generator is designed to change the control parameters of each iteration of the encryption process dynamically, the security of the encryption system is improved; in diffusion layer bit matrix is used to diffuse each block. Real images based simulations results show that the proposed method can resist different attacks and has a high computational efficiency.