Semi-Fragile Watermarking for JPEG Image Authentication: A Comparative Study

One of the ways to protect images from tampering is embedding digital watermarks destroyed by unauthorized changes. The development of digital watermarking methods that are robust against allowable transformations, whose most typical example is lossy compression, presents a challenging task. Such methods and watermarks embedded by them are called semi-fragile. The paper considers different semi-fragile watermarking techniques that resisting JPEG. We focus on the analysis of the effect of watermark capacity, positions of spectral coefficients selected for embedding, and specific algorithms of coefficients modification on the quality of the resulting (secure) image and the authentication accuracy. In the paper, we also provide recommendations on the choice of the best combinations of these parameters depending on the terms of use of a protected image.