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.