Scalable secret image sharing scheme with essential shadows

In scalable (k,n) secret image sharing schemes, original secret image can be partially recovered from any set of k shadows gradually, the entire image can be recovered from n shadows. Recently, (t,s,k,n) secret image sharing with essential shadows were proposed where the n shadows are divided into s essential shadows and n−s normal shadows, secret image can be reconstructed only if there are k or more shadows which include at least t essential shadows. Both the scalable secret image sharing and secret image sharing with essential shadows are practical and attract adequate focus in recent years. In this paper, we propose a new scalable (t,s,k,n) secret image sharing scheme with essential shadows. In our scheme, k or more shadows which include at least t essential shadows can gradually reconstruct secret image, entire secret image can be reconstructed when all s essential shadows are involved. Our scheme combines both features of scalable secret image sharing and secret image sharing with essential shadows, which is reasonable and practical in many applications. The size of shadows in proposed scheme is efficient comparing with previous (t,s,k,n) secret image sharing schemes with essential shadows.