Secret-fragment-visible Mosaic—a New Art and Its Applications to Information Hiding

• Main Authors: Lai, I-Jen, 賴怡臻
• Other Authors: Tsai, Wen-Hsiang
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/97058365171668217409

碩士 === 國立交通大學 === 資訊科學與工程研究所 === 98 === iii created from a grayscale image of a secret document, yielding a steganographic effect of hiding the secret document into the mosaic image, though visibly. The selection of the most similar target image from a database is based on a newly-proposed k-feature of the grayscale value, which speeds up the image creation process. Finally, for secret sharing, a secret image is shared to yield multiple secret-fragment-visible mosaic images. In order to disperse tile images evenly in selected target images, the target images take turns randomly to pick appropriate tile images. In addition, various security enhancement measures were proposed to make the embedded data more random to prevent hackers’ attacks. Experimental results show the feasibility of the proposed methods for image creation and data hiding applications. In this study, a new type of art image is created, which is called secret-fragment-visible mosaic image. And this kind of new mosaic image is used for three applications of data hiding, namely, covert communication, steganography, and secret sharing. First, the newly-proposed secret-fragment-visible mosaic image is created to be composed of rectangular-shaped fragments which come from division of a secret image. A new 1-D h-colorscale is proposed to represent the color distribution of an image based on the color feeling of human vision. To create a secret-fragment-visible mosaic image, a new image similarity measure based on the h-colorscale is proposed, and the most similar candidate image from an image database is selected accordingly as a target image. Then, a greedy algorithm is adopted to fit every tile image in the secret image into an appropriate block in the target image. Furthermore, to solve the problem of using an insufficiently-large database, a remedy method by enlarging the size of a target image is also proposed. Secondly, for covert communication, based on the fact that tile images which are in an identical histogram bin have similar colors, the tile images in an identical histogram bin are reordered, or equivalently, the relative positions of the tile images are switched, to embed secret message bits imperceptibly. Third, for image steganography, a grayscale secret-fragment-visible mosaic image is