New Capabilities of Visual Cryptography
Maged Hamada Ibrahim · 2012
Visual cryptography schemes (VCS) consider the problem of encrypting and sharing images (printed text, hand written notes, pictures, etc.) in a perfectly secure way which can be decrypted directly by the human visual system. A k out of n VCS for is a technique by which a secret image (SI) is shared among n users called share-holders, when k or more users stack their shares (transparencies) together, the SI becomes visible, while k-1 or less users gain no information about SI. This paper presents a strategy by which more than one SI can be shared simultaneously among the n users using exactly the same shares required for the existing (k, n)-VCS without any extra pixel expansions or any other type of overheads over that required for the already existing schemes. The only requirement is a little effort in orienting and distributing the pixels among the shares. The strategy reduces the number of distributed shares required for multiple SI’s and at the same time preserves the perfect security of the existing schemes. Moreover, our strategy enables the visual sharing of a small animated scene.