Visual cryptography for general access structures
Information and Computation
Extended capabilities for visual cryptography
Theoretical Computer Science
Communications of the ACM
Threshold Visual Cryptography Schemes with Specified Whiteness Levels of Reconstructed Pixels
Designs, Codes and Cryptography
Contrast Optimal Threshold Visual Cryptography Schemes
SIAM Journal on Discrete Mathematics
Visual Cryptography II: Improving the Contrast Via the Cover Base
Proceedings of the International Workshop on Security Protocols
A cost-effective encryption scheme for color images
Real-Time Imaging - Special issue on multi-dimensional image processing
Efficient visual secret sharing scheme for color images
Pattern Recognition
Colored visual cryptography without color darkening
Theoretical Computer Science
A multiple-level visual secret-sharing scheme without image size expansion
Information Sciences: an International Journal
Friendly progressive visual secret sharing
Pattern Recognition
Colored visual cryptography scheme based on additive color mixing
Pattern Recognition
A comprehensive study of visual cryptography
Transactions on data hiding and multimedia security V
Enhancing the perceived visual quality of a size invariant visual cryptography scheme
ICICS'12 Proceedings of the 14th international conference on Information and Communications Security
On the security of multi-secret visual cryptography scheme with ring shares
IWDW'12 Proceedings of the 11th international conference on Digital Forensics and Watermaking
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Hou [Visual cryptography for color images, Pattern Recognition 36 (2003) 1619-1629] proposed a four-share visual cryptography scheme for color images. The scheme splits a dithered eight-color secret image into four shares: the black mask and other three shares. It was claimed that without knowing the black mask, no information about the secret image can be obtained even if all the other three shares are known. In this paper, we show that this may be true for a few specific two-color secret images only. In all other cases, however, security cannot be guaranteed. We show that an attacker can compromise a randomly chosen two-color secret image from any two of the other three shares with probability 47 by completely recovering the shape and pattern of the secret image. The advantage will increase to 67 if all the three shares are known. If the secret image has three or four colors, we show that the attacker can compromise it with probability 47 and 835, respectively. Finally, we show that our technique can be extended to compromising secret images with more than four colors.