Abstract: A new concept of pi series is proposed and its chaos-like characteristics have been found by the method of nonlinear time series.Then a new image encryption algorithm based on pi series is proposed to diffuse pixel positions and confuse pixel values.According to the security analysis，the image encryption algorithm demonstrates strong resistance towards exterior attacks such as statistical attacks and differential attacks.

Key words: pi series, chaos-like characteristics, image encryption algorithm, security analysis

摘要： 提出一新的概念——pi序列，并利用非线性时间序列分析方法揭示pi序列的似混沌特性。然后提出一种基于pi序列的图像加密算法，对数字图像分别进行像素位置和像素值扰乱。最后图像加密算法的安全性分析结果表明此加密算法很强地抵抗统计攻击与差分攻击。

关键词: pi序列, 似混沌特性, 图像加密算法, 安全性分析