Abstract: In order to improve the security and efficiency of image encryption algorithm，a dual chaotic system combining piecewise Logistic chaotic map and Cat map is proposed.Firstly，choose a chaotic map from piecewise Logistic chaotic map and Cat map after doing an improved Logistic map，and then confirm the chaotic key.Last，the security analysis is performed at the dual chaotic maps.The experimental result shows that the algorithm has numerous key space，higher sensitivity to initial value and stranger resistant attack ability.It is a novel efficient image encryption algorithm.

Key words: image encryption, chaos, Logistic map, Cat map

摘要： 为了提高图像加密算法的安全性和高效性，提出了一种分段Logistic混沌映射与Cat映射相结合的双混沌系统。首先由改进后的Logistic映射确定选用哪种映射进行迭代，从而确定混沌密钥，最后对算法的安全性进行分析。实验结果表明，该算法的密钥空间较大，并具有较高的初值敏感性和抗攻击能力，是一种新的有效的图像加密算法。

关键词: 图像加密, 混沌, Logistic映射, Cat映射