Date Added: May 2011
Visual cryptography technique allows the visual information to be encrypted in such a way that their decryption can be performed by human visual system. This technique used to encrypt a image into shares such that stacking a sufficient number of shares reveals the secret images. In visual cryptography there are different technique like sub pixel, error diffusion, Boolean operation etc. Visual cryptography can be applied for copyright for images, access control to user images, Visual authentication and identification any kind images of images like (normal or digital). This paper compares various visual cryptography schemes in terms of security, quality of images, contrast, and reliability of images.