Review on Various Visual Cryptography Schemes

Visual cryptography is a powerful technique in which a secret image can be divided into two or more shares and the decryption can be done using human visual system. Visual cryptography has wide range of applications like in biometrics, print online banking, cloud computing, internet voting, etc.. The basic method of visual cryptography is a secret image is hidden into two or more shares which on superimposing will recover the hidden image. During the recovery it is not possible to get the original image due to various reasons like pixel expansion, contrast, storage, security, image types. Therefore various techniques have been developed to address these issues. A survey has been done on various visual cryptography schemes based on the number of secret, pixel expansion, type of share generated, image format, and number of secret image.