02-05-2017, 11:52 AM
A new cryptographic scheme proposed to ensure colour image-based visual cryptographic scheme. A colour image to protect and a binary image used as a key to encrypt and decrypt are taken as input. A secret colour image that needs to be communicated is decomposed into three monochrome images based on the YCbCr colour space. These monochromatic images are then converted into a binary image, and finally the obtained binary images are encrypted using a binary key image, called share-1, to obtain binary cipher images.
To encrypt the exclusive EX operation is performed between binary key image and three secret color image semitones separately. These binary images are combined to get share-2. In decryption the actions are decrypted, then the recovered binary images are inverse in halftone and combined to obtain a secret color image. This scheme is more efficient for the communication of natural images through doubtful channels.
The Visual Cryptography (VC) scheme is used to encode a secret image into several parts, each of which does not reveal any information from the secret image. Actions are printed on transparencies, for example, and distributed to participants. The secret image can easily be deciphered only by betting the parts in an arbitrary order. This property does not need decryption computation. The basic concept of visual cryptography [6] states that a secret message is divided into n partitions, share1, share2, ... and share n, which are seen as random images of noise. Here a secret contains two lighting levels: bright areas are marked with level 0.5 and level 0 is used to represent dark areas.
