基于混沌和置乱双重加密的数字图像水印算法

Digital Image Watermarking by Double Encryption with Chaos and Arnold

提出一种基于离散平稳小波变换的变换域的数字图像水印嵌入和提取算法。本算法先将数字水印图像进行置乱变换(Arnold变换),然后将置乱后的水印图像进行混沌加密,将加密后的水印按行展开成一维行向量,并将像素值从大到小排序,将原始图像平稳小波分解得到的低频系数也按行展开成一维行向量,并按从大到小排序。将排序后的水印图像嵌入排序后的低频系数中,变回二维后结合其它频域重构出水印图像,水印提取是嵌入过程的逆过程,将提取出的水印图像进行混沌解密、Arnold反置乱变换得到原始水印图像。本算法选择了合适的水印嵌入位置,实验结果表明:该算法使图像的不可见性好,而且所嵌入的水印对一般的图像处理攻击如噪声、滤波、旋转、压缩等有较强的鲁棒性。

A new kind of watermark-embedding and detecting algorithm based on stationary wavelet transform was proposed. Firstly, the digital watermarking was transformed randomly （Arnold transformation）, and then encrypted by chaos. The encrypted watermarking was transformed to one-dimensional row vector, and the pixel value was sorted. The coefficient of primitive image of stationary wavelet transformation was expanded to one-dimensional row vector, too, and then the sorted watermarking was embedded to the sorted low frequency and turned to two dimensions. Secondly, the image is reconstructed by coefficients of high-frequency. The process of watermarking extracted is the inversion of the process of watermarking embedded. Finally, the watermarking was withdrawn and the primitive watermarking was obtained after the anti-Arnold transformation. This algorithm chose the appropriate position to embed the watermarking. Experimental results indicate that the algorithm not only enables the watermarking to have the very good invisibility, but also makes the watermarking have very strong robustness to the general image attacks, such as noise, filter, rotation, compression and so on.