Multibit Color-Mapping Steganography Using Depth-First Search

This paper proposes a novel multibit color-mapping steganographic scheme for palette images. Each color in the palette is considered to be a graph node, and a color-graph is constructed according to small color-difference. Some color-nodes in the color-graph are mapped to one bit-sequence with an indefinite length by exploiting a layer-by-layer depth-first search technique. Accordingly, some colors in the palette can be used to represent several secret bits. The major idea of data-embedding process is to modify colors of image pixels. For any pixel to be exploited, a data-hider can always find a bit-sequence mapped by a suitable color that is a prefix of the corresponding secret bit-sequence and replace the original color with the suitable color. Experimental results show that secret data can be embedded and extracted successfully without introducing visual artifacts, and the proposed scheme can gain a larger capacity or maintain quite good image quality.