Print-and-scan counterattacks for plastic card supports Fourier watermarking

In recent past years, Fourier based watermarking techniques have been developed to deal with the print-and-scan attack. In this work, print-and-scan counterattacks for Fourier watermarking are proposed in the context of an industrial application where identity (ID) images are printed and scanned on a plastic card support. The counterattacks are within two stages. The first stage concerns the reduction of image blurring that occurs during the print-and-scan process. Blind restoration and unsharp filters already proposed elsewhere are compared to a Wiener filter adapted to the print-and-scan channel. The second stage deals with the color corrections. These image counterattacks are applied before the watermark retrieval. The proposed method has been experimentally tested on a set of 100 ID images. Results show that the adapted Wiener filter outperforms the blind restoration and unsharp filters in terms of detection rate and distance between empirical probability density functions of correlation values from marked and unmarked images. Finally, the color correction allows a noticeable increase of the overall performances of the method.