An Image Authentication Method by Grouping Most Significant Bits

In 2011, Chan proposed an image authentication method by producing the parity check bits from pixels whose bits have been rearranged. Due to this rearrangement, the value of the most-significant bit of each tampered pixel can be determined according to its parity check bits. With the help of the most-significant bit of the pixel, the pixel can be recovered by selecting two possible (7, 4) Hamming code words. However, if the distance between two Hamming code words is within a certain range, incorrect selection may occur. Chan's method added one additional bit to indicate the correct one. It is trivial that this may degrade the quality of the authenticated image. In this paper, we group four most-significant bits into different groups to form a mapping codebook and the mapping codebook is used to produce authentication data instead of the (7, 4) Hamming code book. The experimental results show that the proposed method has a greater ability to recover tampered areas.