Data Hiding in Non-Expansion Visual Cryptography Based on Edge Enhancement Multitoning

This paper proposes a scheme to hide some extra confidential data in transparencies during secret image encryption in visual cryptography. The secret image is multitoned into several levels first. An extended non-expansion visual secret sharing model is employed, i.e. size of transparencies is equal to that of the secret image. Thus less time and space are needed for transparencies transmission and storage.