A Novel Robust Watermarking Method for Certificates Based on DFT and Hough Transforms

Based on the discrete Fourier transformation (DFT) and Hough transforms, a novel digital watermarking method is proposed. The experiment results show that the algorithm is more robust than the traditional watermark algorithm. The proposed algorithm can endure severe attacks such as printing-scanning, very high loss in its data or data packets, scaling and rotating. The most advantage of the algorithm presented in this paper is that it is robust for the first time of print and scan, but fragile for the second time of print and scan. So this method can be used in the anti counterfeit of certificates.