Data hiding on two stage VQ compression codes

Data hiding in a cover image can be used to protect a confidential message before being transmitted on the Internet. The stego image can be transmitted in either raw or compressed format. The two major concerns about data hiding are hiding capacity and the stego image quality. Higher capacity allows the transmission of more confidential data. A good stego image quality means that it should be visually undistorted and similar to the original cover image to avoid arousing unwanted attention. In this paper, a data hiding strategy is proposed based on two stage vector quantisation (VQ) coding. Data are hidden in both the first stage VQ compression indices and the second stage VQ compression indices. The stego image is transmitted in its VQ compressed format. Experimental results showed that the proposed method resulted in very high data hiding capacity and fairly high stego image quality in comparison to the single stage VQ compression based data hiding strategy.