Raw reversibility of information hiding on the basis of VQ systems

摘要

Up to now, the VQ-based steganographic methods are all lossy approaches since they cannot recover the cover images. Prior studies on reversibility in VQ-based steganography only show the ability to recover the quantized cover images. This paper presents a new two-phase steganographic protocol of genuine VQ-based reversibility, referring to the ability of using a VQ codebook to recover a target cover image and to retrieve all hidden data from the stego-images. The protocol consists of two phases. The Phase 1 generates a stego-image of excellent visual quality; the Phase 2 provides high visual quality and high embedding capacity of the stego-image. Both the stego-images used in the two phases can pass Chi-square test. To evaluate the performance of our method, we have conducted several experiments and compared Phase 1 and Phase 2 of the proposed protocol with two prior studies in reversible steganography based on VQ. The results show that Phase 2 achieves significant improvement on both the embedding capacity and the visual quality of the stego-images. On the other hand, Phase 1 achieves the best visual quality and the lowest embedding capacity of the stego-images. Together with the two phases of the proposed protocol, we can achieve genuine recovery of the cover image of Phase 1. This property cannot be achieved by any combination of prior studies since they all provide low embedding capacity of the stego-images and high difference between the cover image and the stego-image.