Digital image watermarking for photo authentication in Thai national ID card

Problem of fake image in ID card spreads all over the world e.g. false Thai national ID card in Thailand. This problem is quite difficult to detect because appearances of human face always change. Digital image watermarking for photo authentication in Thai national ID card is therefore proposed in this paper to overcome such a problem. Basically, a watermark signal consisting of ID code is embedded into the owner´s picture and printed on ID card. To authenticate a card holder, his shown ID card is taken by a camera in a handheld device, and the watermark detection process is carried out to verify whether the extracted watermark matches the ID code printed on the card. However in practice, distortions introduced to the taken photo directly affect accuracy of the extracted watermark. To minimize these distortions, image registration technique based on projective transformation is applied in order to improve the accuracy of the extracted watermark. Our proposed method is efficient and very practical to implement with the existing watermarking schemes, as shown in the experimental results.