Abstract: A novel image encryption algorithm is presented.The algorithm uses the improved general Arnold map scramble image pixels in the spatial-domain.Then the sequence values of an improved Lorenz chaotic system is adopted to generate keys for the second grayscale image encryption.The key space is large enough to avoid the deciphering by the phase-space reconstruction theory and exhaustive method.The experiment demonstrates the algorithm is effective in the image encryption.The ciphered image has random-like distribution behavior of grey values，adjacent pixels have zero co-correlation properties and the deciphered image is perfect.

摘要： 给出改进的广义 Arnold 映射方程，加快了图像置乱的速度。采用一种改进的Lorenz 三维混沌系统产生的序列作为图像二次加密的密钥，扩大了密钥空间，克服了一维混沌系统不能抵御相空间重构攻击的缺陷。仿真实验表明，该算法可以有效地加密图像，密文具有在整个取值空间均匀分布的特性，相邻像素具有近似于零的相关性，且得到的密文可以无损还原。