Multicast Security and Reliable Transport of Rekey messages over Hybrid Satellite/Terrestrial Networks

Abstract

Security problems in satellite environments are one of the obstacles to the widespread deployment of satellite IP multicast and, more generally, of satellite multimedia applications (Cruickshank et al., 1998). By satellite environments we refer to networks where the satellite plays an essential role. e.g. those where it is used to multicast IP packets to many nodes of a terrestrial network. We also speak of ”Hybrid Satellite/Terrestrial networks” in such cases. The broadcast nature of satellites makes eavesdropping and active intrusion much easier than in terrestrial ルxed or mobile networks. A further issue is speciルc to multicast: the number of members in a multicast group can be very large and, even worse, can change very dynamically. While the process of performing and securing key management for unicast connections is well understood (Harkins & Carrel, 1998), (Maughan et al., 1998), (Orman, 1998), multicast security is still an open ルeld (see par. 2). Protocols that manage the process of distributing keys in a multicast environment are under development (see par. 2.3 and 2.4). Access to the encryption key is controlled by a group key management system, which is responsible for sending the encryption key to authorized new users and for performing multicast group rekeying whenever the key changes. Speciルcally, a group key management system is said to implement two types of access control: backward access control and forward access control. If the system changes the encryption key after a new user joins, the new user will not be able to decrypt past group communications; this is called backward access control. Similarly, if the system rekeys after a current user leaves, or is expelled from the system, the departed user will not be able to access future group communications; this is called forward access control. Many group key management solutions (see par. 2.2, (Jokela, 2006) (Mah, 2004)) have been proposed and a number of classiルcations of the available approaches can be found in the current literature (Dondeti et al., 1999), (Rafaeli & Hutchison, 2003), (Eskicioglu, 2003). Moreover, security mechanisms regarding satellite networks have been investigated in (Howarth et al., 2004), (Noubir & Allmen, 1999) and (Arslan & Alagoz, 2006). Group key management protocols can be categorized as following: