| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 106 === Data hiding (DH) is a significant research field which combines cryptography and digital multimedia processing. DH can widely used in digital multimedia, especially digi-tal images. Matrix code DH (MCDH) by covering function is based on error correcting code, which has high embedding efficiency, and meanwhile decreases the number of modified bits. Up to date, there are already MCDHs proposed. Most researches on MCDH uses using Hamming code, BCH code, and Golay code.
A we-known MCDH is based on Hamming coding HC(n, k), by covering function COV(1, n = 2k − 1, k), which is referred to as HDH. Afterwards, Hamming+ 1 DH (H1DH) was introduced, and it had a better embedding efficiency when compared with HDH. Consider DH on pixel domain. MCDH has a great relation with Least Significant Bit (LSB) and Optimal Pixel Adjustment Process (OPAP). In fact, these methods are very similar, but use different ways for modifying bits.
In this thesis, we propose Hamming+k DH (HkDH) and Hamming+k with m over-lapped pixels DH (Hk_mDH) which integrate the approaches of LSB, OPAP, and H1DH. HkDH may embed 2k secret bits in n pixels. It uses LSB substitution when embedding the first k bit, and then modified 2nd LSB when embed the second k bits. Modifying the 2nd LSB may have collision problem, we can use OPAP to solve it. On the other hand, Hk_mDH embeds 2k bits in (2n – m) pixels. It uses LSB substitution when embed the first k bits. When embedding the second k bits, the modifications in overlapped pixels adopt OPAP. The modifications in other (n – m) pixels still use LSB substitution. For Hk_mDH, we decrease modifications but reduce embedding capacity due to m over-lapped pixels.
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