Abstract: This paper presents a novel image encryption scheme based on a three dimensional Chen system.The three dimensional color image is transformed into a two dimensional grey image.Two chaotic sequences generated from chaotic system are used to shuffle the positions of image pixels from row and column separately.The shuffled image is encrypted，and encrypted image is folded up according to the folding algorithm.Simulation results and security analysis demonstrate that the suggested encryption algorithm of color image deals with image pixels in the 2-D space.This algorithm has the advantages of low computational complexity and memory space，short time，fast speed compared to the encryption algorithm in 3-D space.Moreover，it has good effect and high security through shuffling image pixels of different levels（R，G，B）.

Key words: chaotic system, color image, encrypt

摘要： 提出了一种新的基于三维Chen系统的彩色图像加密算法。将三维空间的彩色图像转换成二维的灰度图像，利用混沌系统生成的混沌序列对二维灰度矩形图分别进行行置乱及列置乱；对置乱后的图像进行加密；按折叠算法对加密后的图像进行折叠处理。仿真结果及安全性分析表明，该加密算法是在二维空间对图像像素进行处理的，相对于三维加密算法而言，降低了算法的计算强度和空间需求，从而减少了运行时间，加快了加密速度；置乱时实现了不同层次（R，G，B）亮度值的完全混合，加密效果好，安全性更高。

关键词: 混沌系统, 彩色图像, 加密