Date Added: Sep 2012
Visual cryptography encodes a Secret binary Image (SI) into shares of random binary patterns. In visual cryptography, the decoding process is performed directly by the human eyes; while in general, the shared images need some processing to reconstruct the secret image. The shares are xeroxed onto transparencies, the secret image can be visually decoded by superimposing a qualified subset of transparencies, but no secret information can be obtained from the superposition of a forbidden subset. Halftone visual cryptography is extended technique in visual cryptography where the random shares are embedded in high quality grayscale images to give them meaning and thus reducing the doubt of eve's droppers that some secure data is hidden.