3GPP Release 15, the first 5G standard, includes protection of user identity privacy against IMSI catchers. These protection mechanisms are based on public key encryption. Despite this protection, IMSI catching is still possible in LTE networks which opens the possibility of a downgrade attack on user identity privacy, where a fake LTE base station obtains the identity of a 5G user equipment. We propose (i) to use an existing pseudonym-based solution to protect user identity privacy of 5G user equipment against IMSI catchers in LTE and (ii) to include a mechanism for updating LTE pseudonyms in the public key encryption based 5G identity privacy procedure. The latter helps to recover from a loss of synchronization of LTE pseudonyms. Using this mechanism, pseudonyms in the user equipment and home network are automatically synchronized when the user equipment connects to 5G. Our mechanisms utilize existing LTE and 3GPP Release 15 messages and require modifications only in the user equipment and home network in order to provide identity privacy. Additionally, lawful interception requires minor patching in the serving network.
In a mobile computing environment, it is desirable to protect information about the movements and activities of mobile entities from onlookers. Solutions to this problem of providing anonymity have to be developed with the constraints of mobile computing environments in mind. In this paper, it is argued that this issue merits investigation. A brief survey of the nature of anonymity provided in proposed or existing mobile computing environments is presented. It is argued further that achieving limited but practical anonymity using standard cryptographic techniques is feasible. Example solutions are presented. In this paper we propose a way to enhance the identity privacy in LTE LTE-Advanced systems. This is achieved while minimizing the impact on the existing E-UTRAN system. This is important since proposals to modify a widely deployed infrastructure must be cost effective, both in terms of design changes and in terms of deployment cost. In our proposal, the user equipment (UE) identifies itself with a dummy identity, consisting only of the mobile nation code and the mobile network code. We use the existing signalling mechanisms in a novel way to request a special encrypted identity information element. This element is protected using identity-based encryption (IBE), with the home network (HPLMN) as the private key generator (PKG) and the visited network (VPLMN) and the private key owner. This allows the UE to protect the identity (IMSI) from external parties. To avoid tracking the “encrypted IMSI” also include a random element. We use this as an opportunity to let the UE include as subscriber-side random challenge to the network. The challenge will be bounded to the EPS authentication vector (EPS AV) and will allow use to construct an online 3-way security context. To complete our proposal we also strengthen the requirements on the use of the temporary identifier (M-TMSI). 