Privacy protection methods for linkability attacks during 5G AKA

5G AKA will be subjected to the linkability attacks like Universal Mobile Telecommunications System (UMTS) Authentication and Key Agreement (AKA)because they inherit the authentication failure messages (MAC failure, Synchronisation failure) from UMTS AKA. The existing method usually uses a key to encrypt the failure message to hide the failure type. However, the attacker can analyze the length of the message to distinguish the failure type and then track the target user equipment (UE). In light of this, this paper provides two privacy protection methods to avoid linkability attacks, which can effectively reduce the possibility of linkability attacks. The construction of the two methods and the corresponding implementation steps are analyzed in this paper.