A visual secret sharing (VSS) scheme is a secret image sharing scheme that divides a secret pixel into several subpixels (the number of subpixels is called the pixel expansion). The secret image encrypted by the VSS technique can be visually revealed without additional computations. However, the contrast of recovered image is poor and thus the VSS framework is always a research issue and does not have practical applications. We introduce a new framework that prioritizes the pixels with different pixel expansions to enhance the image contrast for practical use. Also, by integrating the optical character recognition with the proposed VSS scheme we show a new visual authentication scheme.
Kak's Quantum Key Distribution (QKD) protocol provides not only the distribution but also the integrity of secret key simultaneously in quantum channel; consequently the additional exchange of information, used to check whether an eavesdropper exists, is unnecessary. In this comment, we will point out the failure of Kak's protocol and show that Kak's protocol is no longer provided with the joint distribution and integration that the author declares in .
An efficient quantum key distribution (QKD) protocol has been developed. Results show that our new QKD protocol enhances the efficiency of B92 protocol, a two-state protocol invented by Bennet , from 25% to 28.6%.