Tamper-proof and Recovery of Wavelet-transformed Images

Y.-L. Tang and C.-J. Hung (Taiwan)


Image content authentication, digital watermarking,tamper recovery


In this paper, a recoverable image content authentication algorithm based on digital watermarking is proposed. The host image is first divided into equal-sized blocks and is analyzed to obtain two pieces of information: one for tamper detection and the other for image recovery. For tamper detection, the relations between image blocks are established in order to discourage an adversary's attempt to alter the image. In addition, the authentication system is designed such that it is very insensitive to common image processing operations. For image recovery, in order to achieve a better recovery result, the image blocks with more complex contents (referred to as edge blocks) are further divided into sub-blocks. A non-edge block, if tampered with, will be recovered using its pixel intensity mean embedded previously, while an edge block will be reconstructed by recovering the intensities of its sub-blocks. Due to the different recovery strategies for edge and non-edge blocks, the quality of the reconstructed image is expected to be more satisfactory. Our experiments demonstrated that the proposed algorithm is able not only to detect tampered areas but also to recover the tampered blocks.

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