±1 Steganographic Codes by Applying Syndrome-Trellis Codes to Dynamic Distortion Model in Pixel Chain

Double-layered STC (syndrome trellis code) is the most popular method for minimizing the distortion of ±1 steganography. However, it is a probabilistic algorithm which may fail in the embedding process on some given profiles. Another characteristic of double-layered STC is the high computational complexity. Starting from these two points, we propose a dynamic distortion model defined in a pixel chain in this paper. The dynamic distortion model is working on a principle that the SLSB (second least significant bit) of current pixel is used to control the LSB (least significant bit) of the next pixel. So the distortion of some pixels may be adjusted to zero by this means. We apply STC to fit the dynamic distortion model and get a novel method for ±1 steganography. Comparing with the double-layered STC, the experiment result shows that the proposed method has comparable ability for minimizing distortion with significantly improved embedding speed. And this novel method avoids failure in the embedding process. Considering the advantages together, the method is more suitable for steganography systems and software in practical environment.