A Ramp Model for Distributed Key Distribution Schemes

A Key Distribution Center (KDC) of a network is a server enabling private communications within groups of users. The center provides the secret keys for encrypting and decrypting the messages. A Distributed Key Distribution Center (DKDC) is a set of servers that jointly realizes a Key Distribution Center. In this paper we introduce a ramp model for unconditionally secure Distributed Key Distribution Center. We show lower bounds on the amount of information needed to setup and manage such a DKDC and describe a simple protocol meeting the bounds.