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Capacity-Raising Steganography Using Multi-Pixel Differencing and Pixel-Value Shifting Operations

Yang C-H., Wang S-J., Weng C-Y.

Fundamenta Informaticae

2010

Vol. 98, nr 2/3

321-336

In order to provide large embedding capacity and to minimize distortion for the stegoimage, a steganographic method using multi-pixel differencing is presented in this paper. It takes into consideration four pixels of a block, and the differences between the lowest gray-value pixel and its surrounding pixels are used to determine the degree of smoothness and sharpness for embedding the secret data. If the difference values are large in a block, and the block is located in the sharp area then more data can be embedded. On the other hand, if the block is located in the smooth area less data can be embedded. The multi-pixel differencing method is employed in our scheme. We also propose the pixel-value shifting method to increase the image quality. The experimental results show that our scheme has a large embedding capacity without creating a noticeable distortion.

Codebook-linked Watermarking Scheme for Digital Images

Yang C-H., Weng C-Y., Wang S-J., Sun H-M.

Fundamenta Informaticae

2009

Vol. 92, nr 4

397-409

Digital watermarking techniques are an importantmethod to provide copyright protection of multimedia. In this paper, we proposed a non-embedded watermarking scheme, based on vector quantization (VQ), to protect the image copyright. Our approach applies a codebook to generate a relationship between image blocks and watermark bits, and then the relationship is outputted as the key stream (called KS). With the KS, the relationship between the image and the watermark are confirmed and the copyright of the image is declared. In our method, the number of bits that are related to a block is adaptive. Compared to the scheme of Lin et al., our approach needs only one codebook, while their approach requires seven. Moreover, in our approach each block can be connected with watermark bits, while some blocks can not be connected with watermark bits in their method. Finally, a method of adjusting the robustness is given for our proposed approach. Our approach not only reduces the length of the key stream, but it also allows for a more flexible application. In addition, our experimental results show that the proposed approach runs faster and is more robust than that of Lin et al.