Cryptography Reference
In-Depth Information
(a)
(b)
(c)
(d)
Fig. 13.7. (a) The histogram with the minimum point Z and peak point P .(b)
The histogram with setting minimum point as zero point Z and peak point P .(c)
Shift the points in the range of [P, Z−1] one unit toward zero point Z.(d)The
histogram after embedding.
At the decoder, the proposed method first identifies the twice-embedding
permitted blocks and then retrieves the overhead bits recording information
on the location of the other blocks used for embedding. These are known
as Once-Embedding Permitted Blocks. By overhead bits, Once-Embedding
Permitted Blocks is determined from the unsuitable blocks. The original DCT
coe cients are retrieved by dividing watermarked DCT coe cients by 2.
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