Cryptology ePrint Archive: Report 2006/483

New Constructions for Provably-Secure Time-Bound Hierarchical Key Assignment Schemes

Alfredo De Santis and Anna Lisa Ferrara and Barbara Masucci

Abstract: 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 in the hierarchy can compute 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 use as a building block any provably-secure hierarchical key assignment scheme without temporal constraints and 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. Moreover, the proposed schemes support updates to the access hierarchy with local changes to the public information and without requiring any private information to be re-distributed.

Category / Keywords: Access control, key assignment, provable security, efficient key derivation.

Date: received 22 Dec 2006, last revised 3 Jan 2007

Contact author: masucci at dia unisa it

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Version: 20070103:181025 (All versions of this report)

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