A data embedding method is proposed for image authentication based on table look-up in frequency domain. A visually meaningful watermark and a set of simple features are embedded invisibly in the marked image, which can be stored in the compressed form. The scheme can detect and localize alterations of the original image, such as the tempering of images exported from a digital camera. Keywords: digital watermark, image authentication. 1. INTRODUCTION Digital information revolution has brought about many advantages and new issues. With the ease of editing and perfect reproduction, the protection of ownership and the prevention of unauthorized manipulation of digital audio, image, and video materials become important concerns. Digital watermarking, a scheme to embed special labels in digital sources, has made considerable progress in recent years. There are several categories of watermarking schemes [1]. Among them, fragile watermarking is a technique to insert a signature for image ...