## Cryptology ePrint Archive: Report 2011/049

Unbounded HIBE and Attribute-Based Encryption

Allison Lewko and Brent Waters

Abstract: In this work, we present HIBE and ABE schemes which are unbounded" in the sense that the public parameters do not impose additional limitations on the functionality of the systems. In all previous constructions of HIBE in the standard model, a maximum hierarchy depth had to be fixed at setup. In all previous constructions of ABE in the standard model, either a small universe size or a bound on the size of attribute sets had to be fixed at setup. Our constructions avoid these limitations. We use a nested dual system encryption argument to prove full security for our HIBE scheme and selective security for our ABE scheme, both in the standard model and relying on static assumptions. Our ABE scheme supports LSSS matrices as access structures and also provides delegation capabilities to users.

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Publication Info: this is the full version of a paper appearing in Eurocrypt 2011