Enhanced image secret sharing via error diffusion in halftone visual cryptography

Visual Cryptography is an encryption technique where a secret image is cryptographically encoded into n shares. In visual secret sharing scheme (k, n) the secret images can be visually revealed by stacking together any k or more transparencies of the shares and by inspecting less than k shares one cannot retrieve the secret image. Visual Secret Sharing based on halftone visual cryptography, the continuous-tone image is first transformed into a halftone image, and then encrypted using visual secret sharing schemes. In visual cryptography, meaningless shares are encoded into halftone shares taking meaningful visual information which reduces the suspicion of intruders. These halftone shares are concurrently error diffused to give visually pleasing effect. Error diffusion is computationally efficient with less complexity. Techniques such as classical fixed, edge enhancement, green noise and block error diffusion are performed and a comparative study is made. The quality of the halftone shares enhanced by using Floyd - Steinberg and Jarvis error filters. Secret image is reconstructed by stacking the qualified halftone shares. The simulation results shows that the visual quality of the obtained halftone share are observably better.