Optimal (2, n) visual cryptographic schemes

Mausumi Bose, Rahul Mukerjee
2006 Designs, Codes and Cryptography  
In (2, n) visual cryptographic schemes, a secret image(text or picture) is encrypted into n shares which are distributed among n participants. The image cannot be decoded from any single share but any two participants can together decode it visually, without using any complex decoding mechanism. In this paper, we introduce three meaningful optimality criteria for evaluating different schemes and show that some classes of combinatorial designs, such as BIB designs, PBIB designs and regular graph
more » ... designs, can yield a large number of black and white (2, n) schemes that are optimal with respect to all these criteria. For a practically useful range of n, we also obtain optimal schemes with the smallest possible pixel expansion.
doi:10.1007/s10623-006-0011-9 fatcat:f5sdoxq26rbdhfjpxpsbrc4icq