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Berkeley, California

Oct. 21, 2006 to Oct. 24, 2006

ISBN: 0-7695-2720-5

pp: 27-38

Craig Gentry , Stanford University, USA

Zulfikar Ramzan , Symantec, Inc.

David P. Woodruff , MIT, USA; Tsinghua University, China

DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/FOCS.2006.27

ABSTRACT

A family of subsets C of [n] \underline{\underline {def}} {1, . . . , n} is (r, t)- exclusive if for every S \subset [n] of size at least n - r, there exist S_1, . . . , S_t \in C with S = S_1\cupS_2\cup? ? ? \cupS_t. These families, also known as complement-cover families, have cryptographic applications, and form the basis of informationtheoretic broadcast encryption and multi-certificate revocation. We give the first explicit construction of such families with size poly(r,t)n^{r/t}, essentially matching a basic lower bound. Our techniques are algebraic in nature. <p>When r = O(t), as is natural for many applications, we can improve our bound to poly(r,t)\left( \begin{gathered} n \hfill \\ r \hfill \\ \end{gathered} \right)^{1/t}. Further, when r, t are small, our construction is tight up to a factor of r. We also provide a poly(r, t, log n) algorithm for finding S_1, . . . , S_t, which is crucial for efficient use in applications. Previous constructions either had much larger size, were randomized and took super-polynomial time to find S_1, . . . , S_t, or did not work for arbitrary n, r, and t. Finally, we improve the known lower bound on the number of sets containing each i \in [n]. Our bound shows that our derived broadcast encryption schemes have essentially optimal total number of keys and keys per user for n users, transmission size t, and revoked set size r.</p>

INDEX TERMS

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CITATION

Craig Gentry,
Zulfikar Ramzan,
David P. Woodruff,
"Explicit Exclusive Set Systems with Applications to Broadcast Encryption",

*FOCS*, 2006, 2013 IEEE 54th Annual Symposium on Foundations of Computer Science, 2013 IEEE 54th Annual Symposium on Foundations of Computer Science 2006, pp. 27-38, doi:10.1109/FOCS.2006.27