A New Approach for Delegation Using Hierarchical Delegation Tokens

In this paper we give a classiication of delegation schemes into four main classes. To solve the problem with simply chained tokens in cascaded delegations we introduce the concept of hierarchical delegation tokens. To realize this concept we use the Schnorr signature scheme and self{certiied public keys introduced by Girault. We describe the rst approach for hierarchical key generation based on an unregarded idea of G unther and the generation of designated veriier signatures. Using these tools, we present eecient delegation schemes for the four main classes, which are eecient in generating and using delegation keys compared with other existing approaches. This is one of the few works, that combines cryptographic algorithms and protocols to beneet for the complexity and the eeciency of the resulting delegation mechanisms.