Image authentication and recovery scheme based on watermarking technique

Actually digital images are used to show some important evidences, however once they are propagated through an open channel such as Internet, these images are easy targets of malicious modification. In this paper, we propose a watermarking based image authentication scheme, in which owner's blocks of interest are authenticated using embedded watermark. If the scheme determined that these blocks were modified intentionally, the resume of the original version of these blocks is recovered without any additional information. Also the embedded watermarks are enough robust to no-intentional attacks, such as JPEG compression and noise contamination. In the watermark embedding process, watermark sequence is extracted from the blocks of interest of the image and it is embedded into the corresponding DCT blocks indicated by a previously generated mapping list. In the authentication and recovery process, the watermark sequence is extracted from the corresponding DCT blocks and then it is compared with the sequence extracted from the blocks of interest to determine its authenticity. The proposed system use only a secret key to generate the mapping list to map owner's blocks of interest and other blocks. The evaluation results show efficient authentication and recovery capacity of the proposed scheme.