Abstract: A type of chaotic system with variable parameter is presented to improve the complexity and pseudo-randomness of chaotic system，via analyzing and advancing the ordinary classical chaos systems.Theoretical analysis and simulation experimental results testify that the chaotic system has better chaotic characters than several traditional chaotic systems.Moreover，a class of image encryption algorithm，image dual scrambling encryption algorithm based on chaotic system with variable parameter，is proposed by improving the traditional image encryption algorithms based on chaos，which uses the chaotic system to scramble pixel positions and pixel values.The experimental results show that the algorithm has stronger resistance against attacks such as exhaustion attack，count attack，cropping attack，noise attack，which is consequently of higher security and efficiency.

Key words: image encryption, variable parameter chaotic system, dual scrambling

摘要：

为提高混沌系统的复杂性和伪随机性，通过分析和改进常用的经典混沌系统，设计了一种变参混沌系统，理论分析与仿真测试结果表明其具有更好的混沌特性。并对传统的基于混沌的数字图像加密算法进行改进，提出了一种基于变参混沌系统的图像双重置换加密算法，将这种变参混沌系统应用于数字图像像素位置与像素值双重置换的加密算法中。仿真实验表明：这种加密算法具有较强的抵御穷举攻击、统计攻击、裁减攻击、噪声攻击性能，其安全性与效率均比较高。

关键词: 图像加密, 变参混沌系统, 双重置换