Content fragile watermarking based on a computer generated hologram coding technique

In this paper we present a content fragile watermarking based on a computer generated hologram coding technique. Content fragile watermarking techniques aim to prevent tampering and fraudulent use of modified images. A content fragile watermark monitors the integrity of the content of the image but not its numerical representation. Therefore, the watermark is designed so that the integrity is proven if the content of the image has not been tampered with. However, if parts of the image are replaced, the watermark information should indicate evidence of forgery. Using computer generated hologram watermarking, the embedded mark could be easily recovered by means of a Fourier transform. Due to this fact the host image can be tampered with and watermarked with the same holographic pattern. To avoid this possibility we have introduced an encryption method using a private key. The proposed technique is suitable for use for freelancers’ photography authentication. It could be applied to colour images as well as to grey-scale ones. The proposed schema is based on the knowledge of the original mark from the authentication entity, to apply image correlation between this and the extracted one.