Self-embedding fragile watermarking with restoration capability based on adaptive bit allocation mechanism

In this paper, we propose a novel fragile watermarking scheme with content restoration capability. Authentication-bits are produced using the image hashing method with a folding operation. The low-frequency component of the nonsubsampled contourlet transform (NSCT) coefficients is used to encode the restoration-bits for each block by the adaptive bit allocation mechanism. During the bit allocation, all the blocks are categorized into different types according to their degree of smoothness, and, complex blocks, which are deemed to have higher priority than smooth blocks, are allocated more bits. Two algorithms are utilized to adjust the block classification and the binary representations in order to guarantee that the numbers of the self-embedding authentication-bits and restoration-bits are exactly suitable for 1-LSB embedding capacity. On the receiver side, the extracted authentication-bits and the decoded restoration-bits are used to localize and restore the tampered blocks, respectively. Due to the low embedding volume, the visual quality of the watermarked image is satisfactory. Experimental results also show that the proposed scheme provides high restoration quality.

► NSCT coefficients are utilized to encode the restoration-bits efficiently. ► We use bit allocation mechanism to adjust block types and binary representations. ► Quality of the watermarked image is good due to 1-LSB embedding volume. ► Our scheme can provide higher restoration quality after tampering localization.