A broadcast key distribution scheme based on block designs
A key distribution scheme for broadcast encryption is proposed. It is based on block designs. In this scheme a centre provides each user (receiver) of the system with a set of keys. If at a later stage, some users are no longer entitled to the messages, they should also no longer be able to decrypt them. This should even be the case if these illegitimate users can form a coalition and exchange the keys that they have obtained before (provided that the size of this coalition does not exceed some value).
By means of block designs a tradeoff can be made between the size of the largest admissible coalition and the total length of the keys that each user has to store. The proposed system is unconditionally secure and seems better suited for large coalitions than existing schemes.
Key wordskey distribution broadcast encryption s-resilience connectivity fractional covering block design
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- 1.A. Fiat and M. Naor, “Broadcast Encryption,” Advances in Cryptology, Proc. CRYPTO'93, D. R. Stinson, Ed., Lecture Notes in Computer Science 773, Springer Verlag, Berlin, pp. 480–491, 1994.Google Scholar
- 2.E. F. Assmus and J. D. Key, Designs and Their Codes, Cambr. Univ. Press, 1993.Google Scholar
- 4.S. K. Stein, “Two combinatorial covering theorems,” J. Comb. Theory, Ser. A, 16, 391–397, 1974.Google Scholar