Extended Visual Cryptography for Color Shares using Random Number Generators

Abstract: Visual cryptography is a special image encryption technique. It is different from traditional cryptography, because it does not need complex computation to decrypt. The benefit of the visual secret sharing scheme is in its decryption process where without any complex cryptographic computation encrypted data is decrypted using Human Visual System (HVS). But the encryption technique proposed here uses a new k-n secret sharing scheme for color image where encryption (Division) of the image is done using Random Number generator and to decrypt the image at least a group of k shares out of n shares reveals the secret information, less of it will reveal no information. The concept of visual information pixel (VIP) synchronization and error diffusion is used to attain a color visual cryptography encryption method that produces meaningful color shares with high visual quality. VIP synchronization retains the positions of pixels carrying visual information of original images throughout the color channels and error diffusion generates shares pleasant to human eyes. Comparisons with previous approaches show the superior performance of the new method.

Keywords: Color meaningful shares, digital halftoning, error diffusion, random number, secret sharing, visual cryptography (VC).