标记视觉密码是一种在分享份中嵌入标签为用户提供补充信息的视觉密码方案，现有的标记视觉密码方案存在着恢复秘密图像视觉效果较差、像素扩展以及需要设计加密矩阵等问题.为此，提出一种改进的基于异或解密的标记视觉密码方案.加密时，在生成的普通分享份中嵌入标记信息；解密时使用异或解密.通过该方案解密后的图像既不存在像素扩展问题，又不需要设计加密矩阵，同时还可以调节嵌入标记信息的概率.与现有的标记视觉密码相比，该方案恢复的图像更加清晰.
Tagged visual cryptography is a new type of visual cryptography, which can hide tags into each generated common share to provide users with supplementary information. The existing tagged visual cryptography has some problems such as poor visual quality, pixel expansion and design of encryption matrices. Therefore, this paper proposes an improved tagged visual cryptography based on XOR decryption. In encryption process, the scheme embeds tagged information in the generated common share; and in decryption process, XOR operation is used to recover the secret image. The scheme decrypts the image without pixel expansion problem, and the requirement of design of encryption matrices. At the same time, it can adjust the probability of embedded tagged information. Compared with the existing tagged visual cryptography, the image recovered by the scheme is clearer.
[1] 文昌辞,王沁,苗晓宁,刘向宏,彭阳翔. 数字图像加密综述[J]. 计算机科学,2012, 39(12):6-9. Wen C C, Wang Q, Miao X N, Liu X H, Peng Y X. Digital image encryption:a survey[J]. Computer Science, 2012, 39(12):6-9. (in Chinese)
[2] Naor M, Shamir A. Visual cryptography[C]//Advances in Cryptology-Eurocrypt'94. Berlin:Springer, 1994:1-12.
[3] Kafri O, Keren E. Encryption of pictures and shapes by random grids[J]. Optics Letters, 1987, 12(6):377-379.
[4] Chen T H, Tsao K H. Threshold visual secret sharing by random grids[J]. Journal of Systems and Software, 2011, 84(7):1197-1208.
[5] Chao H C, Fan T Y. Generating random grid-based visual secret sharing with multi-level encoding[J]. Signal Processing:Image Communication, 2017, 57:60-67.
[6] Chao H C, Fan T Y. Random-grid based progressive visual secret sharing scheme with adaptive priority[J]. Digital Signal Processing, 2017, 68:69-80.
[7] Yan X, Wang S, El-Latif A A A, Niu X. Visual secret sharing based on random grids with abilities of AND and XOR lossless recovery[J]. Multimedia Tools and Applications, 2015, 74(8):3231-3252.
[8] Yan X, Wang S, Niu X. Threshold visual secret sharing based on Boolean operations and random grids[C]//International Conference on Neural Information Processing. Cham:Springer, 2014:620-627.
[9] Wu X, Sun W. Improved tagged visual cryptography by random grids[J]. Signal Processing, 2014, 97:64-82.
[10] Ren Y, Liu F, Lin D, Feng R, Wang W. A new construction of tagged visual cryptography scheme[C]//International Workshop on Digital Watermarking. Cham:Springer, 2016:433-445.
[11] Shyu S J. Image encryption by random grids[J]. Pattern Recognition, 2007, 40(3):1014-1031.
[12] Yan X, Wang S, El-Latif A A A, Niu X. Random grids-based visual secret sharing with improved visual quality via error diffusion[J]. Multimedia Tools and Applications, 2015, 74(21):9279-9296.
[13] Guo T, Liu F, Wu C K. K out of k extended visual cryptography scheme by random grids[J]. Signal Processing, 2014, 94:90-101.
[14] Paknahad S M, Hosseini S A, Alagheband M R. User-friendly visual secret sharing for color images based on random grids[C]//IEEE 201610th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP), 2016:1-6.
[15] Wu X, Sun W. Improving the visual quality of random grid-based visual secret sharing[J]. Signal Processing, 2013, 93(5):977-995.
