A Die-Hellman based Key Management Scheme for Hierarchical Access Control

Abstract. All organizations share data in a carefully managed fashion by using access control mechanisms. We focus on enforcing access con-trol by encrypting the data and managing the encryption keys. We make the realistic assumption that the structure of any organization is a hi-erarchy of security classes. Data from a certain security class can only be accessed by another security class, if it is higher or at the same level in the hierarchy. Otherwise access is denied. Our solution is based on the Die-Hellman key exchange protocol. We show, that the theoretical worst case performance of our solution is slightly better than that of all other existing solutions. We also show, that our performance in practical cases is linear in the size of the hierarchy, whereas the best results from the literature are quadratic