A Robust Digital Watermarking Scheme and Its Application in Certificate Verification

This paper presents a new approach for the certificate verification based on digital watermarking. An invisible watermark is embedded in the owner digital photo of the certificate with different strength according to the characteristics of human vision system (HVS). During verification the owner photo is scanned, the watermark extracted from the scanned photo is compared with the original watermark. Several techniques are used to detect and invert geometric transformations of the watermarked images undergone by the printed and scanned process so that the embedded watermark can be successfully determined. Experiment results have demonstrated the feasibility of the proposed approach that has the advantages of high security, high flexibility and low cost.