Visual cryptography scheme (VCS) shares a binary secret image into multiple shadows, only qualified set of shadows can reveal the secret image by stacking operation. However, VCS suffers the problems of low visual quality of the revealed image and large shadow size. A (t, k, n) XOR-based visual cryptography scheme (XVCS) shares the secret image into n shadows including t essentials and n-t non-essentials. A qualified set of shadows contains any k shadows including t essentials. The revealing process is implemented by XOR operation on the involved shadows. In this paper, we propose a construction method for (t, k, n)-XVCS with essential shadows. The secret image can be revealed perfectly, and the shadow size is small compared with VCS. Theoretical analysis and experimental results show the security and effectiveness of the proposed scheme.

视觉密码方案（VCS）将二进制秘密映像共享为多个阴影，只有合格的一组阴影才能通过堆栈操作显示秘密映像。然而，VCS遭受所显示图像的视觉质量低和阴影尺寸大的问题。一种（t，k，n）基于XOR的视觉加密方案（XVCS）将秘密图像共享到n个阴影中，其中包括t个基本要素和n - t个非基本要素。一组合格的阴影包含任何k个阴影，其中包括t要领。通过对涉及的阴影进行XOR运算来实现显示过程。在本文中，我们提出了一种具有必要阴影的（t，k，n）-XVCS的构造方法。秘密图像可以完美地显示出来，并且阴影大小比VCS小。理论分析和实验结果表明了该方案的安全性和有效性。