基于小波变换的置乱-扩散算法的研究

在图象分级的基础上，利用小波变换的原理，对小波变换后的每个子图象进行置乱操作，这样在逆变换还原图象时，图象中的每个点不仅位置发生了改变，而且灰度值也发生了改变，使算法达到很好的置乱效果．通过将随机选用的置乱矩阵与迭代的次数作为密钥，提高了算法的安全性．实验证明，置乱后还原的图象清晰度高，算法抗攻击能力强，可适用于图象加密和图象隐藏的预处理过程．

Image Scrambling and Gray-level Diffusion Algorithm Based on Wavelet Transform

Based on image hierarchy, all sub-images generated by wavelet transform are scrambled. When the scrambled sub-images are combined to form a complete image through reverse wavelet transform, both pixel locations and gray-levels are changed. Therefore, the algorithm achieves good scrambling effects. By using randomly selected scrambling matrix and the number of iterations as secret keys, the algorithm's security is improved. Expriments have proved that the recovery of scambled imgaes is hidh-fidelity and the algorithm is strong in resisting attackes. The proposed algorithm can be used as an image encryption algorithm, or can be used to hide images during pre-processing.