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In order to authenticate the content of the image and find out the tampered location, semi-fragile watermark technology usually extracts feature information from image blocks as watermark, which will be embedded into irrelevant blocks by block mapping algorithm. When a block is tampered, its original feature hidden in other blocks will not be changed. However, it must be pointed out that this situation only considers that the original feature information of the tampered block has been tampered, but ignores that the feature information of other blocks embedded in the tampered position is also destroyed. It is impossible to recognize that whether the tampered area itself or the image block whose feature information embedded in the tampered area is tampered, resulting in increasing of false detection rate. In order to improve the accuracy of tamper detection of semi-fragile watermark algorithm, this paper proposes a novel tampering detection algorithm, which performs multi-scrambling encoding on the extracted feature information, and establishing a tampering equation related to each block according to the multi-scrambling encoding. According to the sum of tampering equation to determine whether the image block has been tampered. Experimental results show that after using the tampering detection algorithm proposed by this paper, both the false rejection probability and false acceptance probability are lower than the previous algorithms. In addition, the false acceptance probability is still very low under JPEG compression.
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