Recovering secret image in Visual Cryptography

Security has become an inseparable issue even in the field of space technology. Visual Cryptography is the study of mathematical techniques related aspects of Information Security which allows Visual information to be encrypted in such a way that their decryption can be performed by the human visual system, without any complex cryptographic algorithms. This technique represents the secret image by several different shares of binary images. It is hard to perceive any clues about a secret image from individual shares. The secret message is revealed when parts or all of these shares are aligned and stacked together. In this paper we provide an overview of the emerging Visual Cryptography (VC) techniques used in the secure transfer of the thousands of images collected by the satellite which are stored in image library and sent to Google for use on Google Earth and Google maps. The related work is based on the recovering of secret image using a binary logo which is used to represent the ownership of the host image which generates shadows by visual cryptography algorithms. An error correction-coding scheme is also used to create the appropriate shadow. The logo extracted from the half-toned host image identifies the cheating types. Furthermore, the logo recovers the reconstructed image when shadow is being cheated using an image self-verification scheme based on the Rehash technique which rehash the halftone logo for effective self verification of the reconstructed secret image without the need for the trusted third party(TTP).