A New Steganographic Method for Palette-Based Images.
Jiří Fridrich · 1999
In this paper, we present a new steganographic technique for embedding messages in palette-based images, such as GIF files. The new technique embeds one message bit into one pixel (its pointer to the palette). The pixels for message embedding are chosen randomly using a pseudorandom number generator seeded with a secret key. For each pixel at which one message bit is to be embedded, the palette is searched for closest colors. The closest color with the same parity as the message bit is then used instead of the original color. This has the advantage that both the overall change due to message embedding and the maximal change in colors of pixels is smaller than in methods that perturb the least significant bit of indices to a luminance-sorted palette, such as EZ Stego [1]. Indeed, numerical experiments indicate that the new technique introduces approximately four times less distortion to the carrier image than EZ Stego. The maximal color change is 4−5 times smaller for the new technique than that of EZ Stego. A technique that introduces less distortion to the carrier image will generally cause changes that are more difficult to detect, and will therefore provide more security.