The Application And Research Of Visual Cryptography

With the rapid development of the Internet, information as a kind of resource is getting more and more attention. This also presents a great challenge to the researchers in the field of information security. The visual cryptography, which is proposed by Naor and Shamir in 1995, is a new branch of cryptography, which provides a new method for protecting the secret information. Visual cryptography can encrypt text, binary images, grayscale images and other objects, and then distribute the shared images to many participants, thus ensuring the security of secret information. The recovery of the secret information is obtained by the simple superposition of the shared images. Participants do not need to understand any of the cryptography knowledge, so that the visual password can be used by various groups of people. This paper study the problem of visual effect and the problem of encryption capacity in the field of visual cryptography based on OR, and propose schemes of high visual quality and multi secret sharing. The main contents are as follows:(1) A simple summary of the existing visual cryptography scheme based on OR operation. And the problem of the existing problem is analyzed: the problem of the pixel expansion in the visual cryptography scheme of single secret image sharing; the problem of angle in visual cryptography scheme of multi-secret image sharing; the visual quality problem exists in visual cryptography scheme.(2) Aiming at the problems of large pixel expansion and pool visual quality of reconstructed image in the existing visual cryptography schemes, A new(K, K) visual cryptography based on dynamic sharing is designed. The scheme can improve the visual quality by using the matrix set and the random function to select the different matrix to share different block. At the same time based on the pixel block of the encoding operation to ensure that the scheme without pixel expansion. The experimental results of(4, 4)-VCS show that the scheme have no expended and high-efficiency.(3) A(2, N-1, N) multi secret visual cryptography scheme is proposed for the problem of angle and the visual quality in multi-secret visual cryptography. In the scheme, the image quality of the reconstructed image is improved by using the characteristic of multilevel contrast, and the relation of the adjacent shared image is used to share the multi-secret images. Experimental schemes(2,3,4) were used to demonstrate the scheme’s multi-secret characteristics and high visual quality characteristics.