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Print-and-Scan Resilient Watermarking for Authenticating Paper-Based Certificates

As digital technologies advance, it is very easy to forge a paper-based certificate or images to deceive people, and the counterfeits look almost the same as the originals. Because such forgery causes tremendous losses to the society, the demand for automatic and on-line authentication of paper-based images has been increasing. To solve such a problem, watermarking techniques against the “print-and-scan” attack have been studied extensively. In this paper, a print-and-scan resilient watermarking technique operating in the discrete Fourier transform (DFT) domain is proposed. By embedding a set of peaks as a watermark into the selected DFT coefficients, the watermark is robust against the print-and-scan attack. The experimental results demonstrate that the proposed algorithm can correctly detect the embedded watermark from a printed-and-scanned image. Such a system is thus very useful to prevent forgery by providing on-line, real-time, and automatic authentication of paper-based certificates.