New fragile watermarking method for stereo image authentication with localization and recovery

To address issues of image authenticity verification and integrity protection, a fragile watermarking method for stereo image authentication is proposed with stereo matching technique. According to stereo matching of left and right images, non-overlapping blocks of left image are classified into non-matchable and matchable ones. Right image blocks and non-matchable blocks of left image are categorized into smooth, texture and complex blocks considering their roughness. Then, the corresponding alterable-length watermark is computed based on the results of block classification, and the destroyed blocks are recovered by using the corresponding alterable-length watermark. Besides, matchable tampered blocks of left image are recovered with the matched contents in right image. A detection technique with the part of alterable-length watermark is used to increase accuracy of tamper localization at the receiver. The disparity can be used to recover the tampered matchable block. Therefore, the quality of watermarked images is improved because of low embedding capacity. Additionally, the alterable-capacity watermark provides suitable information for smoother images with fewer bits and we obtain high quality restoration. Experimental results show that the proposed method can not only localize the tampered regions precisely but also recover the tampered regions with higher quality compared with the state-of-the-art methods. (C) 2014 Elsevier GmbH. All rights reserved.