Extended Visual Cryptography Techniques for True Color Images

Abstract

In the digital era, Internet is the basic necessity for exchanging any multimedia data over the widespread network. As long as the communication network is untrusted, data security and privacy plays a major role. Images are important form of multimedia data which are excessively transferred over the Internet. Various techniques and algorithms have been proposed by researchers to securely transmit the images over the network while performing very less computations during encryption=decryption. Visual Cryptography provides basic and convenient way to share the secret and confidential images with ease. Various Visual Cryptography Techniques and Extended Visual Cryptography Techniques for binary, gray-scale and colored images have been proposed by researchers to improve the security and contrast of the reconstructed image. Two new (k, n)-EVCTs for true color images are proposed in this thesis work. First technique is (3, 3)-EVCT and second one is (2, 3)-EVCT. Both techniques share a single secret true RGB color image at a time. In (3, 3)-EVCT, three meaningful shares are generated i.e., R share, G share and B share. 3-out-of-3 shares are required to regenerate the original secret image on the receiver side. Less than three shares would not be able to regenerate the original secret image. In (2, 3)-EVCT, generated shares are RG share, GB share and RB share. At least any 2-out-of-3 shares are required to regenerate the original secret image. Both techniques are efficient, simple and convenient to use. The reconstruct image generates without any loss in image size, contrast, resolution and visual quality. The techniques are also compared with various existing techniques to show their effectiveness.