数字水印技术被视为一种有效的数字图像版权保护技术，但当水印信息因嵌入算法的公开而被一些攻击所破坏时，或同一幅图像被嵌入多个不同水印时，都不能有效地检测出数字作品的所有者。提出了一种基于[WTBZ]Trace变换和标识信息的数字图像版权保护算法。该算法基于Trace变换进行数字作品的特征提取，并在第三方机构进行登记注册从而获得标识信息，然后根据标识信息确认数字作品的所有权。文中给出了算法的实验结果，并与传统的几何矩不变量算法进行了比较，结果表明，该算法对旋转、缩放、剪切及其组合、仿射变换、去掉部分行等几何攻击以及滤波和JPEG压缩攻击具有更高的稳健性。

Watermarking scheme is a well known method for copyright protection of images. However, we can not identify who the real owner is if multiple watermarkings are embedded in an image or the embedding algorithm of watermarking has made public because some attacks can destroy the watermarking. In this paper, a robust copyright protection scheme for digital images that combines trace transform and timestamp technique is proposed. Firstly, the features of the image are extracted using the trace transform. Then the message is registered at the fair third party in order to gain the timestamp. Finally, we can use the timestamp to prove who the real owner is. Experimental results are given and compared with the results of the method based on the geometric moment invariants. The results show that the scheme can well withstand geometrical attacks such as rotation, scaling, shearing, combined attack, affine transform, remove lines, filter and JPEG lossy compression.