基于位平面置乱和灰度值双向扩散的图像加密算法

提出一种基于位平面置乱和灰度值扩散的图像加密算法.对灰度图像高四位比特位平面分别用不同参数的Arnold映射进行置乱,低四位的比特位平面则保持不变.利用分段线性混沌映射产生伪随机的灰度值序列对置乱后的图像进行一个双向灰度值的扩散.通过高四位比特位平面的置乱和灰度值的双向扩散,使密文图像和明文图像的各种统计特性有了显著的差别,取得很好的加密效果.论文对加密算法的安全性进行了详细的分析,包括密钥敏感性分析、密钥空间分析、统计分析、差分攻击分析,信息熵分析等.数值实验结果表明,本文的图像加密算法具有密钥空间大、密钥敏感性强、可以抵抗统计分析攻击、蛮力攻击、差分攻击等优良特性.

Image Encryption Algorithm Based on Bit-plane Scrambling and Grayscale Bidirectional Scatter

Image encryption algorithms based on bit-plane scatter are proposed. The Arnold mapping is applied to scrambling and grayscale scramble the four most significant bits in grayscale images with different parameters while the four least significant bits are not changed. Piecewise linear chaos mapping is applied to generate pseudo random grayscale sequences and the grayscale bidirectional scatter is applied to the scrambled images. With scrambles in the four most significant bits and the grayscale bidirectional scatter, the statistical characteristics of plain images and cipher images display great differences. In this paper, the safety of encryption algorithm is analyzed, including the analysis of secret key sensitivity, analysis of secret key space, statistical analysis, analysis of difference attack and entropy of information. In this paper, the secret key space is large and the secret key sensitivity is high in the image encryption algorithms. The algorithms are robust against the attack of statistical analysis and difference attacks.