A quadratic-residue-based fragile watermarking scheme

A new fragile watermarking scheme for image authentication and location of areas that have been tampered with is proposed in this paper. Based on a quadratic-residue theorem, the proposed scheme generates the watermark block-by-block in the cover image. To improve security by preventing malicious attacks, such as the vector quantization attack, a pseudo-random number generator using a private key as a seed is applied in the embedding process. The experimental results show that our proposed scheme is effective in image authentication and maintains high image quality in the watermarked images. In addition, areas that have been tampered with can be located and at least approximately recovered.