Communications in Unknown Networks: Preserving the Secret of Topology

Cryptography investigates security aspects of data distributed in a network. This kind of security does not protect the secrecy of the network topology against being discovered if some kind of communication has to be established. But there are several scenarios where even the network topology has to be a part of the secret. In this paper we study the question of communication within a secret network where all processing nodes of the network have only partial knowledge (e.g. given as routing tables) of the complete topology. We introduce a model for measuring the loss of security of the topology when far distance communication takes place. We will investigate lower bounds on the knowledge that can be deduced from the communication string. Several kinds of routing tables are not sufficient to guarantee the secrecy of topology. On the other hand, if a routing table allows to specify the direction from which a message is coming from we can run a protocol solving the all–to–all communication problem such that no processing node can gain additional knowledge about the network. Finally, we investigate the problem, whether a knowledge base can be generated from local knowledge of the processing nodes without losing the state of secrecy. It will be shown that this is not possible for static networks and most kinds of dynamic networks.