IMSI-based Routing and Identity Privacy in 5G

In 5G, identity privacy of a user is proposed to be protected by concealing the identifier of the user. In order to route the concealed identifier to the appropriate destination, certain information about the international mobile subscriber identity (IMSI) - country code and network code, need to be revealed. But, as was recently pointed out, the routing of requests for authentication information between visited and home network and also within the home network, needs more information about the IMSI to be revealed. It was also recently pointed out that there are restrictions on user identity privacy due to lawful interception in the serving network. In this new context, we reexamine published alternative solutions of identity privacy. We find the previously promising solutions e.g., solution based on public key of home network become less promising. We find the solution based on identity based encryption becomes more promising than it was before.