抗裁剪的DWT域CDMA扩频图像水印

提出一种具有抗裁剪自同步性能的DWT(Discrete Wavelet Transform)域DS-CDMADirect Sequence Code Division Multiple Access)扩频图像水印算法.该算法具有如下特点:1)在嵌入过程中,首先对水印数据进行CDMA扩频编码:在DWT的LL3子带隐藏水印信息的同时,按一定结构模式嵌入同步信号,使水印具有自同步能力;2)在水印的盲检测过程中,先搜索同步信息并对任意裁剪攻击后的图像进行准确定位,再进行CDMA解码检测出水印信息.算法利用DWT的时频局部特性,有效地提高在变换域内搜索同步信号的效率.实验证明,采用本算法生成的水印信息不仅对JPEG(Joint Picture Expert Group)压缩、Gaussian噪声攻击等具有很好的稳健性,特别在抗裁剪攻击方面有比较明显的效果.

DWT-Based CDMA Watermarking Resist Cropping

This paper proposes a discrete wavelet transform (DWT)-based image watermarking algorithm using direct sequence code division multiple access (DS-CDMA) techniques, to resist cropping attack. The CDMA encoded watermark bits, concatenated by the synchronization code, are embedded into the selected DWT coefficients of the original image. During the blind recovery of the embedded data, the corresponding DWT coefficients of the cropped watermarked image are relocated by self-synchronizing efficiently, and then the correlation between the extracted watermark information and Gold sequence is analyzed. By exploiting the time-frequency localization characteristics of DWT, the computation load to search the synchronization code is reduced. The experiment results demonstrate that the generated watermark is robust to cropping, joint picture expert group (JPEG) compression, Gaussian noise and other common attacks.