Encode the binary message “01” in the four blocks of four samples each – “10 25
ID: 3846948 • Letter: E
Question
Encode the binary message “01” in the four blocks of four samples each – “10 25 9 35, 20 16 14 2, 14 24 26 15, 13 5 23 17” – by encoding each bit in a pair of blocks and using an error resistance threshold of S = 2 (each sample in a block being shifted proportionally with the square root of its distance from the closest edge of the block). What is the minimum encoding threshold, T, needed to allow for hiding the two bits? What is the advantage of hiding a bit in a pair of blocks vs. hiding each bit in a block?
Explanation / Answer
Reversible data hiding scheme is the technique that
allows embedding data inside an image and later the
hidden data can be retrieved as required and the exact copy
of the original host image is recovered. Some of the
traditional reversible data hiding schemes are based on
modulo-arithmetic additive and spread-spectrum
techniques [1,2]. An example of these schemes is the one
proposed by Honsinger et al., which based on addition of
modulo 256 as an invertible operation [2]. Although some
of these schemes are robust, the modulo-arithmetic-based
reversible data-hiding algorithms have the disadvantage of
salt-and-pepper visual artifacts and hinder watermark
retrieval [3].
In order to enhance the robustness of the reversible
watermarking and reduce the salt-and- pepper visual
artifact of the above mentioned schemes, histogram
shifting techniques were proposed. In this scheme, the
embedding target is replaced by the histogram of a block of
the image. A good example of the scheme is the circular
interpretation scheme proposed by Vleeschouwer et al. [4,
5]. Although this type of data hiding schemes provides a
higher quality of the embedded image, the embedding
capacity is lower [6]
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