ABSTRACT
Widespread on the Internet GIF format images, the page, the ad universal application, is an excellent secret carrier. The GIF image information hiding algorithm can be classified into three cases: change in the color palette, change in the color palette and the index value, and change in the index value. Change the color palette is relatively simple and easy to implement. Typical of these algorithms is freeware Gif-Shume. The idea is to rearrange the color palette, with dierent combinations of colors to hide information. After the image data are hidden, the information is not changed, only the palette of colors is sequentially changed. This algorithm is limited by the capacity of the size of the palette, GIF image palette with approximately 256 colors, regardless of the image file size; the maximum capacity of only log2(256!)=210 hidden bytes, so the usefulness of this method is not strong. With the same principle, the method changes the color palette and index values are as follows: First, the extract color palette by dithering algorithm, and then slightly modified color extended to the entire palette, according to the index value and the information bit comparison, the index value represents information with the same information bit is not to be replaced, otherwise, the index value is replaced with the index value to another. This method is also referred to as jitter modulation method. S-Tools software applications and Hide & Seek is this principle, but these methods cause a significant reduction in the color palette and reduce the quality of the image. Using a common software, the image palette can easily find abnormality of such an algorithm and thus secure poor. In addition, these indexed color images are the secret method for resistance and the band training wavelet detection algorithm is weak.
