数字水印技术是实现多媒体数据版权保护的一种有效手段。随着关系型数据库的广泛使用，也随之产生了在关系型数据库中嵌入水印信息的需求。通过在关系型数据库中所嵌入的版权信息，可以将数据库与其拥有者联系起来，从而实现数据库的版权保护。本文提出了一种可以在数据库中嵌入具有实际意义字符串的水印算法，并介绍如何通过调整算法中的参数，实现不同的鲁棒性和不可见性需求。在Oracle数据库中所进行的仿真实验结果表明，该算法可以在实际数据库中得到很好的应用。

A method of embedding a digital watermark image in video is proposed in this paper. By two- dimensional and three-dimensional multiresolution signal decomposing, the decomposed watermark images with different resolution are embedded in the corresponding resolution of the decomposed video. To enhance the robustness of watermarking, the watermark information is coded by error correction coding of Hamming code in our algorithm. Experimental results show that the proposed technique is robust enough against the attacks of frame dropping, averaging and lossy compression.

Digital watermarking has been presented in recent literatures as a technique to protect the copyright of multimedia data. But most of these literatures focus on the algorithms of embedding one-dimensional watermarks or two-dimensional binary digital watermarks. In this paper, a method of embedding a gray-level digital watermark into an image is proposed. By stack filter's threshold decomposition technique, a gray-level digital watermark is decompounded into a series of binary digital images for implementing multiple watermarking. The experimental results show that the proposed techniques are successfully tolerant to reasonable image processing operations and the lossy compression techniques such as Joint Photographic Experts Group (JPEG).

A digital watermarking technique based on the discrete fractional Fourier transform (DFRFT) is proposed. The original image is transformed by DFRFT, and the DFRFT coefficients of the original image are modified by the information of watermark. Experimental results show that the proposed technique is robust to lossy compression attack.