为了增强水印的稳健性和提高运算速度,提出了一种应用直接序列扩频的码分多址通信技术(DS-CDMA)的图象离散小波变换域水印算法.该算法先采用m序列优选对来生成正交的Gold序列集,然后将改进后的Gold序列对水印信息进行扩频,并形成互相叠加的.CDMA编码,最后将其嵌入到原始图象的DWT变换域.在水印提取时,则利用正交码的自相关函数特性来检测出扩频到Gold码的水印信息,从而实现了隐藏信息的盲检测.与已报道的同类算法的性能比较表明,应用该算法隐藏的水印信息量较大,且水印稳健性好.

Theory and method in digital communication have been applied effectively to the embedding and detection of digital watermark. The method is efficient to embed the watermark bits into the digital media by the principle of CDMA communication due to its many advantage, such as, multiple-accessing, excellent secrecy, standing firmly against disturbing, and resisting noise attacks etc. In this paper, a DWT-based image watermarking algorithm applying DS-CDMA is proposed. The orthogonal Gold sequences sets generated via the preferred-pair of m sequences are well improved, and then are used to spread spectrum of the watermark. The CDMA encoded watermark is embedded into the DWT domain by modulating selected DWT coefficients of the image in a fashion similar to CDMA. Blind recovery of the embedded data is achieved by analyzing the DWT coefficients of the watermarked image and the auto-correlation of orthogonal codes. The proposed algorithm is compared with the existing watermarking schemes based on CDMA. The experiment results demonstrate that the watermark with the proposed algorithm is robust to JPEG compression, Gaussian noise and other typical attacks. The hidden information is secure well and hard to resist by unauthorized detection and attacks because of the same private key.