中文摘要：

针对传统的基于视觉密码的图像秘密共享方案存在像素扩张导致其只能共享小尺寸的秘密图像、信息隐藏效率较低的问题,提出一种能够提高信息隐藏容量的（t,k,n）多重门限图像秘密共享方案.该方案利用秘密图像信息控制视觉密码方案中共享矩阵的选取,从而实现秘密图像在视觉密码方案中的隐藏.在秘密图像恢复的第一阶段,任意t个参与者直接叠加其影子图像后可以视觉解密出低质量的秘密图像信息;在第二阶段,任意k个参与者可以从影子图像中提取出隐藏的信息,并通过计算恢复出精确的灰度秘密图像.相对于传统的视觉密码方案,本文方案在不影响视觉密码恢复图像的视觉质量前提下,可以隐藏更多的秘密图像信息,而像素扩张尺寸较小.

英文摘要：

From the point of view of information hiding,traditional visual cryptography scheme（VCS） is not an efficient method.It can only share a small sized secret image due to the large pixel expansion.A（t,k,n） multi-threshold image secret sharing scheme is proposed to increase the amount of hidden information.A grayscale secret image is hidden in a VCS to guide the choice of share matrices.In the first phase of the reconstruction process,any t participants can stack their shadow images to decode a vague secret image by human visual system.In the second phase,any k participants can extract additional information hidden in their shadow images,and reveal a precise grayscale secret image by computation.Compared with the traditional VCS,the proposed scheme can hide more information of the grayscale secret image,and has smaller size expansion without deteriorating the visual quality of the revealed image of VCS.