对一种基于混沌映射的对称图像加密算法的改进

文1]提出了一种基于3D Cat映射的对称图像加密算法，文2]对其安全性进行了分析，指出该算法在抗选择明文攻击能力方面性能比较差。本文在文1]的基础上，提出了一种改进的对称图像加密算法。在本算法中，通过复合离散混沌系统隐藏混沌序列产生时所经历的迭代次数，来避免文2]的基于符号动力学的密码分析。理论分析和仿真实验表明，本文提出的改进算法在保持了原来算法的各种抗攻击能力性能的同时，进一步提高了原算法的抗选择明文攻击能力。

A Modified Symmetric Image Encryption Scheme Based on Chaotic Map

In ref. 1], a symmetric image encryption scheme is proposed, which is based on 3D chaotic cat maps. In ref. 2], a security analysis has been carried out for the scheme, and pointed that the performance is poor in resistance of chosen plain image attack. Hence, in this letter, a modified symmetric image encryption scheme is presented. In the proposed scheme, when the chaos sequence is generated, the iteration times are hidden to avoid cryptanalysis based on symbolic dynamic. Theoretical analyses and simulated experiment show that, the modified scheme enhances the resistance of chosen plain image attack. At the same time, which also preserves the good performance against others attacks.