Simulating BPP using a general weak random source
SFCS '91 Proceedings of the 32nd annual symposium on Foundations of computer science
Visual cryptography for general access structures
Information and Computation
Randomness in distribution protocols
Information and Computation
Constructions and Bounds for Visual Cryptography
ICALP '96 Proceedings of the 23rd International Colloquium on Automata, Languages and Programming
Contrast-Optimal k out of n Secret Sharing Schemes in Visual Cryptography
COCOON '97 Proceedings of the Third Annual International Conference on Computing and Combinatorics
On the program size of perfect and universal hash functions
SFCS '82 Proceedings of the 23rd Annual Symposium on Foundations of Computer Science
SFCS '89 Proceedings of the 30th Annual Symposium on Foundations of Computer Science
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A visual cryptography scheme for a set P of n participants is a method to encode a secret image into n shadow images called shares each of which is given to a distinct participant. Certain qualified subsets of participants can recover the secret image, whereas forbidden subsets of participants have no information on the secret image. The shares given to participants in X ⊆ P are xeroxed onto transparencies. If X is qualified then the participants in X can visually recover the secret image by stacking their transparencies without any cryptography knowledge and without performing any cryptographic computation. This is the first paper which analyzes the amount of randomness needed to visually share a secret image. It provides lower and upper bounds to the randomness of visual cryptography schemes. Our schemes represent a dramatic improvement on the randomness of all previously known schemes.