Digital image content authentication addresses the problem of detecting any illegitimate modification on the content of images. To cope with this problem, a novel semifragile watermarking scheme using the pinned sine transform (PST) is presented in this paper. The watermarking system can localize the portions of a watermarked image that have been tampered maliciously with high accuracy as well as approximately recover it. In particular, the watermarking scheme is very sensitive to any texture alteration in the watermarked images. The interblock relationship introduced in the process of PST renders the watermarking scheme resistant to content cutting and pasting attacks. The watermark can still survive slight nonmalicious manipulations, which is desirable in some practical applications such as legal tenders. Simulation results demonstrated that the probability of tamper detection of this authentication scheme is higher than 98%, and it is less sensitive to legitimate image processing operations such as compression than that of the equivalent DCT scheme.