Mutual Authentication between Aerial Base Stations and Core Network: A Lightweight Security Scheme

The 3rd Generation Partnership Project (3GPP) is actively working on incorporating non-terrestrial networks (NTNs) into the 5G system. NTNs integrate various aerial and space components like uncrewed aerial vehicles (UAVs), airships, and satellites to offer flexible solutions for extending the ground systems. In the context of aerial radio access networks (ARANs), aerial base stations (ABSs) are deployed in clusters. However, due to the dynamic nature of ABSs, additional identity authentication is required between user equipment (UE), core network (CN), and ABSs. It is crucial to design lightweight authentication protocols that are subject to the limited computing resources and energy constraints of UAVs. We observe that aerial facilities possess multiple attributes, which can be leveraged to integrate identity authentication of the involved entities based on specific attribute sets. This study proposes an attribute-based authentication and key agreement protocol for ABSs and the CN, utilizing ciphertext-policy attribute-based encryption (CP-ABE). This approach enables access control based on physical attributes, ensuring secure communication and identity authentication in the ARANs. The protocol reduces the need for repeated execution of the authentication and key agreement (AKA) protocols between UE and the CN during ABS replacement. It employs elliptic curve cryptography (ECC) and fixed-length keys to minimize computational overhead during decryption, and also supports mutual authentication between ABSs during UE handover. We simulated the protocol on standard curve P-256, P -384, P-521 encryption performance, and analyze the relationship with attribute universe size. The design aligns with the 3GPP specifications, aiming for practical field application in the future.