Abstract:
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 Centers. In the ramp approach, the required resources (randomness, information storage, messages to be exchanged, ...) can be reduced at the cost of a security degradation which depends on the size of the coalition of users who tries to break the scheme. 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.