Abstract: A secret gray-level image sharing scheme based on a(n,n)-threshold, divides a secret gray-level image into n meaningful gray-level shadow images using recover function and error diffusion algorithm. In order to increase the steganographic effect for the security protection purpose, the proposed scheme selects n gray-level images containing meaningful contents as shadows. The proposed scheme can generate the shadow image with good visual quality by using error diffusion algorithm. The generated shadow image has no pixel expansion,and its size is ectual to the secret image's. Furthermore, the reconstructing process is fast and lossless. Experimental results and theoretical analysis demonstrate that the proposed scheme offers a high secure and effective mechanism for secret image sharing.

Key words: Secret gray-level image sharing, Lossless reconstructing, Meaningful shadows, Error diffusion, Recovery function