基于半色调技术的(2,2)可视密码方案

为解决传统可视密码像素膨胀及分存图像无意义等问题,提出一个基于半色调技术的（2,2）可视密码方案。方案中密图为黑白反色图像,利用半色调技术将一幅灰度图像处理后的半色调图像作为掩盖图像一,然后对其进行反色运算得到掩盖图像二,根据密图修改掩盖图像生成分存图像,叠加分存图像恢复密图。该方案符合可视密码解密简单的特性且分存图像有意义、没有引入任何像素膨胀。

(2,2)Visual Cryptography Schemes based Halftoning

Conventional Visual Cryptography Scheme suffers from complicated construction method,pixel expansion and meaningless share images.To resolve these problems,a（2,2） VCS with covert image based halftoning is introduced.In this scheme,the concealed secret image must be the special black-white image.Halftoning is used to convert a grey covert images to the first halftone covert images,then reversed it to get the second.Two share images will be attained by modifying the halftone covert images referring to the secret image. Stacking the two share images will reveal the secret image. Experiments have shown the proposed scheme absolutely accords with the merit of VCS that decoding is very easy. Furthermore, the construction method of the proposed scheme is simpler and the achieved shares are meaningful without any pixel expansion.