DCT Based Semi-Fragile Watermarking Technique

This paper introduces a DCT based semi-fragile watermarking for image content authentication. The embedding algorithm is based on some invariant properties in JPEG compression to get robustness against JPEG compression. The watermark includes authentication bits and recover bits. The authentication bits are block self-embedded and have the ability of detecting and localizing unacceptable tamper in image, while the recover bits are used to reconstruct the tampered area approximately. The impact of integer rounding error is analyzed,and the convergence of iteration process is demonstrated. The experimental results demonstrates that the proposed algorithm can tolerate the distortion under certain JPEG compression and AWGN, and can effectively detect, localize and restore the tampered area.