Progressive visual cryptography with watermarking for meaningful shares

Abstract

Progressive Visual Cryptography (PVC) is a special encryption technique which can be utilized to recover the secret image gradually by superimposing more and more shares. If we only have a few pieces of shares, we could get an outline of the secret image; by increasing the number of the shares being stacked, the details of the hidden information can be revealed progressively. PVC using unexpanded shares regenerates images of high quality. But this method is insecure as the shares generated are noise like images and have more interest of hackers as they treat them as critical information in the transmission. If the random looking shares are enveloped into some meaningful images the interest of hackers can be reduced. In the proposed method, a digital watermarking technique is used to generate meaningful shares. The secret image shares are watermarked with different cover images and are transmitted. At the receiving side the cover images are extracted from the shares and stacked one by one which reveals the secret image progressively. This scheme provides a more efficient way to hide images in different meaningful shares providing high security and recovered image with high contrast.