A Novel Secured Transmission Of Color Extended Visual Images Using Error Diffusion

Cryptography is the science of writing in secret code and is an ancient art. Cryptography not only protects data from theft or alteration, but can also be used for user authentication.visual cryptography is a technique which allows visual information to be encrypted in such a way that the decryption can be performed by the human visual system. This paper introduces the concept of visual information pixel (VIP) synchronization and error diffusion with which high visual quality of images can be obtained. VIP synchronization retains the positions of pixels and error diffusion generates shares pleasant to human eyes. Basic visual cryptography is expansion of pixels. It uses two transparent images out of which one contains random pixels and the other contains secret information. Colour visual cryptography encrypts a colour secret message into n halftone image shares. It uses the additive and subtractive color models. Unlike the present system, it uses k-out ofn scheme in which any n shares can be present for the decryption. This system enhances the color quality of an image along with maintaining the security in the scheme. Presently a technique called watermarking is being used which means to make the data as small as possible. Now visual cryptography has been introduced as an extension to watermarking.