Analysis and Design on Key Updating Policies for Satellite Networks

Satellite networks are becoming increasingly important because of the ex- citing global communication services they provide. Key management policies have been successfully deployed in terrestrial networks to guarantee the information se- curity. However, long propagation, storage and computation constraints bring new challenges in designing efficient and cost-effective key updating policies for satellite networks. Based on the structure and communication features of satellite networks, a dynamic key management model for satellite networks (DKM-SN) is presented, which includes certificates owned by each satellite, primary keys and session keys both of which are shared between two satellites. Furthermore, a protocol is designed for updating certificates for satellites; different policies for updating primary and ses- sion keys are studied and their efficiency and security are analyzed and compared. In addition, simulation environment for satellite networks is built and the key updat- ing processes are implemented in Walker constellation. From the simulation results, further contrasts on key updating time and storage costs between the applications of IBM hybrid key management model (HKMM) and DKM-SN in satellite networks are presented. Finally, important suggestions in designing key updating policies are Satellite networks are composed of various kinds of communication satellites, vehicles and constel- lations. It contains both satellite-to-satellite and satellite-to-ground links. Satellite networks integrate terrestrial systems and all sorts of satellites which are deployed in different orbits with diverse tasks. Nowadays, satellite networks are increasingly used in the long-distance information transmission ser- vices. In order to ensure the message confidentiality, integrity and nonrepudiation, as well as efficiency of communication, a key management mechanism should be used to provide data encryption, authenti- cation and key distribution and updating services for satellite communication. Key management model defines the entities in the services, the categories and relationships of the keys, and the key updating protocols and algorithms. In contrast with terrestrial networks, satellite networks are subject to dynamic network topology, long propagation delay, as well as low computing and storage capabilities of satellites. Due to these constraints, efforts should be made to decrease the key updating time in order to reduce the communication cost. Besides, for those keys used to encrypt large amount of information, the key up- dating protocols should be based on symmetric encryption techniques for the sake of computation cost. The storage cost on satellites should also be reduced by efficiently lowering the number of the keys. Currently, key management policies for terrestrial networks are comparatively sophisticated. There are generally three kinds of key management policies, including those that use symmetric key encryption techniques, public key encryption techniques and combination of the two. For example, Kerberos (1) uses symmetric key encryption techniques and a KDC (Key Distribution Center); both symmetric and public key encryption techniques are adopted in IBM hybrid key management model (HKMM) in which three kinds of keys including session key, primary key and public key are used. Based on different net- work features and environments, the number of entities and encryption techniques involved in updating a certain type of key may be very different. For instance, though both for updating the session key, Neuman-Stubblebine protocol (3) includes three parties while Janson-Tsudik protocol (4) involves only