An extensive review on visual cryptography schemes

Visual Cryptography is a special kind of cryptographic technique in which the decryption can perform by the human visual capability. In general, for some critical security issue the visual cryptography scheme is used, for example to identify the difference in human and machine. Similarly some other applications also use the visual cryptography schemes like scanning and printing, captcha etc. Hence the researchers developed many methods and techniques for the visual cryptography schemes. This paper is intended to study the various visual cryptography schemes and also to analysis the performance on the basis of expansion of pixel, number of secret images, image format and type of share generated. In addition we present a concise description about the instructions for future research.