Roaming Security in 5G Systems

Abstract

The Next Generation Critical Communication (NGCC) system in Norway (“Nødnett”) will be using mobile systems as its basis. In particular, it appears that Nødnett will be realized as a Home Environment (HE) with its own network functions, but it will not feature the serving network (SN) functions or the radio access network (RAN) part. Thus, the Nødnett system will rely on a roaming agreement with one or multiple existing operators. However, “national roaming” will also be permitted for Nødnett, which means that Nødnett users will be permitted to use other networks if the preferred one is unavailable. Altogether, this means that roaming and roaming security are very important for Nødnett. In this paper, we investigate and evaluate the state of the art of 5G roaming security, and its application to Nødnett. Roaming, in 5G, is conducted over the N32 interface. Thus, we investigate the security of the “Protocol for N32 INterconnect Security” (PRINS) and the use of TLS over the N32 interface. The PRINS protocol also permits so-called IPX operators (roaming brokers) to be part of the exchange, which potentially creates additional problems for the Nødnett use cases.