10-04-2017, 07:55 PM
Most visual cryptographic methods are available for black and white images. For grayscale images, the semitone is used to transform a gray level image into a two-level image. After the visual cryptographic methods can be applied directly to the semitone images. In this work, we used block replacement crosslinking media that provide more semitone image size compared to the source image. After it was applied (n, n) Visual Cryptography based Alignment Actions encryption method. By applying this process, we encrypt the gray level image using visual cryptography in an easy way. Visual Cryptography is a new cryptographic technique used to protect images. In visual cryptography the image is divided into parts called actions and then distributed to participants. The decryption side only by stacking the shared images gets the image. The initial model developed only for bi-level or binary images or monochrome images. Later progressed to adapt to colour images means images of gray and RGB / CMY images. For RGB / CMY images different methods are developed based on the techniques of colour decomposition. The pixel expansion and the quality of the reconstructed secret image have been an important subject of the visual secret exchange schemes (VSS). A series of probabilistic VSS schemes with minimal pixel expansion for black and white (binary) secret images have been proposed.
