new constructions for provably-secure time-bound hierarchical key assignment schemes
A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class can derive the keys of all classes lower down in the hierarchy, according to temporal constraints. In this paper we propose new constructions for time-bound hierarchical key assignment schemes which are provably secure with respect to key indistinguishability. Our constructions exhibit a tradeoff among the amount of private information held by each class, the amount of public data, the complexity of key derivation, and the computational assumption on which their security is based.
key assignment provable security access control