In this thesis, an effective block-based fragile watermarking method for image tamper detection and self-recovery is proposed. The proposed scheme embeds watermarks consisting of the authentication data and the recovery data into image blocks. To tamper detection and self-recovery, the embedding sequence is generated by using chaotic map and intensity-relation check to thwart various malicious attacks. In the tamper detection process, a hierarchical tamper detection strategy is adopted to achieve high tamper detection accuracy. A two-level self-recovery scheme is proposed by considering the 3×3 block-neighborhood to solve tampering coincidence problem. To reduce the smoothing blocking effect of recovered images, the wavelet transform coefficient is used to recover tampered image. It enhances the image contrast rather than using the average as recovery data. Experimental results show that the proposed scheme can effectively resist collage attack, vector quantization (VQ) attack and constant-average attack, while sustaining superior accuracy of tamper localization. Furthermore, the results show that the tampered images can be successfully self-recovered with high visual contrast.
