Time-storage trade-offs for cryptographically-enforced access control

Abstract

Certain classes of authorization policies can be represented as a directed graph and enforced using cryptographic techniques. Such techniques typically rely on the authorized user deriving a suitable decryption key using a secret value and public information. Hence, it is important to find enforcement schemes for which little public information is required and key derivation is efficient. These parameters are related to the number of edges and the distance between nodes in the graph associated with the authorization policy. In this paper we consider ways in which two particular types of authorization graph can be rewritten so that the number of edges and the greatest distance between any two nodes are reduced, thereby providing the basis for more efficient cryptographic enforcement. © 2011 Springer-Verlag.