Achieving Secrecy in Visual Secret Sharing Scheme Using Encrypted Images

Abstract

Visual cryptography (VC), an emerging cryptography technology, uses the characteristics of human vision to decrypt encrypted images. Cryptography is the study of mathematical techniques related to aspects of information security such as confidentiality, data security, entity authentication, and data origin authentication, but it is not the only means of providing information security, rather one of the techniques. VC is a new technique that provides information security which uses simple algorithms unlike the complex, computationally intensive algorithms used in other techniques like traditional cryptography. Previous methods in the literature show good results for black and white VC schemes, however, they are not sufficient to be applied directly to shares due to different structures. Some methods for color VC are not satisfactory in terms of producing either meaningless shares or meaningful shares with low visual quality, leading to suspicion of encryption. Visual secret sharing encrypts a secret message into halftone image shares. This article introduces the concept of visual information pixel (VIP) synchronization and error diffusion to attain a visual cryptography encryption method that produces meaningful shares with high visual quality. VIP synchronization retains the positions of pixels carrying visual information of original images throughout the channels and error diffusion generates shares pleasant to human eyes. Comparisons with previous approaches show the superior performance of the new method.