Dual semi-fragile Watermarking based on Discrete Cosine Transform for Detect and Recover Tampered Region in Color and Gray Images

Digital image watermarking is a common topic in the field of information security and image abuse prevention on the internet and communication areas. One of the applications of digital watermarking is authentication and recovery tampered region. These methods can discover correctness and integrity of the received image by using information which is embedded.In this paper, a method is proposed to identify and recover tampered regions in both color and grayscale images. The proposed method provides a second chance for recovery of tampered region, based on the ability of dual watermark embedding in the image. In addition, due to use of discrete cosine transform, it improves robustness against compression. In order to guarantee the security of embedded watermark, a chaotic map is used with a secret key which is transferred with the image. In this proposed method, to prevent copy-move attack, the information which is embedded for detection of tampered block depends on its own key. The experimental results show that the proposed method can correctly identify the tampered region under a compression with a quality factor of more than 30. This means the reduction of the false-positive error, and also the recovery of the tampered regions where half of the image is destroyed with structuralsimilarity index about 0.9.