| dc.description.abstract | Visual cryptography is a technique that applies the human visual system to decode
encrypted information, such as text, image and number, without any sophisticated
devices and computing capabilities. Therefore, compared with the traditional cryptography,
it is apparent that it saves a large amount of time and money on devices and
computations. Also, visual cryptography provides the convenience for humans to carry
out decryption with a portal card which is significant to the business application. In
the past decade, visual cryptography has been thoroughly researched not only on its
contrast and subpixel expansion, but also on its applications.
The main contribution of this thesis is the security of visual cryptography related
to the dishonest shareholders. This is the first known work concerning this variety
of potentially secure problem. In the previous papers, the shareholders are inherently
honest. However, in the real world, it is impossible to guarantee that every shareholder
would be honest forever(e.g., because of the interest of business or military, some
shareholders might change to be the traitors). Therefore, a new method based on
visual authentication[16] is proposed and the improvement is also made. In this thesis,
we also review the previous papers on different fields of the visual cryptography. | |
