New Condition for Hierarchical Secret Image Sharing Scheme

Recently hierarchical threshold secret image sharing (SIS) scheme was proposed to provide hierarchical access structures to the conventional SIS. These hierarchical access structures are more adequate than the conventional SIS in many practical situations. However in the actual hierarchical SIS scheme, even if the access condition is not satisfied, the secret image is visually leaked, which is very serious security deficiency of this SIS scheme. The present work proposes a new condition for the hierarchical threshold SIS scheme to guarantee the secrecy of the secret image when the access condition is not satisfied. The experimental results show the functionality of the SIS with the proposed condition, in which if the access condition is satisfied then the secret image is recovered in lossless manner, otherwise only pseudorandom pattern is extracted.