Date Added: Jan 2011
In this paper, the authors 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. The constructions avoid these limitations. They use a nested dual system encryption argument to prove full security for the HIBE scheme and selective security for the ABE scheme, both in the standard model and relying on static assumptions.