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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.

Embedding Invisible Watermarks into Digital Images Based on Side-Match Vector Quantization

Wu H.-C., Chang C.-C.

Fundamenta Informaticae

2004

Vol. 63, nr 1

89--106

This paper proposes an effective digital watermarking scheme to protect the intellectual property rights of digital images. This scheme embeds representative watermarks into images during the process of side-match vector quantization (SMVQ) compresses and extracts the digital watermark effectively in order to determine the ownership of the image when a dispute over intellectual property rights occurs. The method proposed in this paper embeds a watermark based on the grouping of the codewords in a state codebook, and it stresses the fact that the SMVQ compressed image and the decompressed image both contain watermarks. In addition, the decompressed image has strong resistance against being damaged. Even under JPEG lossy compression, the watermark can still be restored effectively. The proposed method enables the watermark to be embedded directly into a compressed image that is much smaller than the original one. Once applied to the network, the method can save time in image transmission as well as storage space.