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Three-Phase Lossless Data Hiding Method for the VQ Index Table

Chang C-C., Lin C-Y., Hsieh Y-P.

Fundamenta Informaticae

2008

Vol. 82, nr 1-2

1-13

Hiding Data in a cover image often applies a steganographic technique that makes the stego image appear as similar to the original cover image as possible. Conventional VQ-based (vector quantization) steganographic methods typically involve codeword replacements to hide secret bits. Such replacements may cause serious distortion or a perceptible block effect on the stego image. In this paper, we propose a three-phase steganographic method for the VQ index table. Instead of applying codeword replacements, the proposed method uses different coding schemes-SOC, SMVQ, and VQ-to imply the secret bits. The quality of the stego image generated by the proposed method is completely equal to that of the original cover image (i.e., the VQ cover image). Experimental results have shown that the proposed method has the best stego image quality compared with other methods. In addition, the proposed method provides adaptive embedding capacity and compression bit rate according to predefined thresholds.

VQ Codebook Searching Algorithm Based on Correlation Property

Chang C-C., Lu T-C., Ya J-B.

Fundamenta Informaticae

2007

Vol. 76, nr 1-2

39-57

In this paper, we shall present two efficient codebook-matching schemes with a locally adaptive vector quantizer (LAVQ) and a search-ordering coding vector quantizer (SOCVQ) to be applied in the Vector Quantization (VQ) encoding system. The proposed codebook-matching schemes exploit the correlation property between adjacent image blocks so that the process of codebook matching can be speed up. Simulation results show that the time complexity of the proposed schemes is lower than those of PCA, Multipath TSVQ, and DPTSVQ. Moreover, the image quality of the proposed methods is close to those processed by the other methods.