# A Secure Blockchain-Based Authentication and Key Agreement Scheme for 3 GPP 5G Networks
###### Abstract  
The futuristic fifth-generation cellular network (5G) not only supports high-speed internet, but must also connect a multitude of devices simultaneously without compromising network security. To ensure the security of the network, the Third Generation Partnership Project (3 GPP) has standardized the 5G Authentication and Key Agreement (AKA) protocol for mutually authenticating user equipment (UE), base stations, and the core network. However, it has been found that 5G-AKA is vulnerable to many attacks, including linkability attacks, denial-of-service (DoS) attacks, and distributed denial-of-service (DDoS) attacks. To address these security issues and improve the robustness of the 5G network, in this paper, we introduce the Secure Blockchain-based Authentication and Key Agreement for 5G Networks (5 GBA). Using blockchain as a distributed database, our 5G-BACentralizes authentication functions from a centralized server to all base stations. It can prevent single-point-of-failure and increase the difficulty of DDoS attacks. Moreover, to ensure the data in the blockchain cannot be used for device impersonation, our scheme employs the one-time secret hash function as the device secret key. Furthermore, our 5G-BACentralizes can protect device anonymity by mandating the encryption of device identities with Subscription Concealed Identifiers (SUCI). Linkability attacks are also prevented by deprecating the sequence number with Elliptic Curve Diffie-Hellman (ECDH). We use Burrows-Abadi-Needham (BAN) logic and the Scyther tool to formally verify our protocol. The security analysis shows that 5G-AKA is superior to 5G-AKA in terms of perfect forward secrecy, device anonymity, and mutual Authentication and Key Agreement (AKA). Additionally, it effectively deters linkability attacks, replay attacks, and most importantly, DoS and DDoS attacks. Finally, the performance evaluation shows that 5G-BACentralizes is efficient for both UEs and base stations with reasonably low computational costs and energy consumption. 5G; 5G-AKA; authentication; blockchain; BAN logic; Scyther 202222022202220220220220222022222222222222222222222222222222222222222222222222222222222222222222222222222221515151515151515151515  
Partnership Project (3 GPP) has standardized a new Authentication and Key Agreement (AKA) protocol known as 5G-AKA in TS 33.501 [2]. 5G-AKA can mutually authenticate base stations, 5G core networks, and user equipment (UE). It has resolved some pre-existing security issues found in the 4G Long-Term Evolution (LTE) networks. For example, by encrypting the permanent identity of the UE using the Subscription Concealed Identifier (SUCI), 5G-AKA can prevent International Mobile Subscriber Identification (IMSI), catching attacks and rogue base station attacks [3]. However, as some of the authentication methods in 5G-AKA are inherited from the 4G EPS-AKA [4], security issues in 4G networks remain unsolved in 5G-AKA. For example, 5G-AKA suffers from linkability attacks, in which malicious users can track a specific device by using synchronization error messages [5]. Additionally, it lacks perfect session key forward secrecy that guarantees data confidentiality, even if the long-term key is stolen in the future [3]. Furthermore, 5G-AKA is a centralized protocol that relies heavily on two functional entities, namely the Authentication Server Function (AUSF), and the Authentication credential Repository and Processing Function (ARPF) located inside the Unified Data Management (UDM) server. As there will be a tremendous number of devices connecting to the same 5G core network, 5G-AKA would be highly vulnerable to Denial of Service (DoS) attacks and Distributed Denial of Service (DDoS) attacks which aim to paralyze functional entities in the core network. Consequently, the existing 5G-AKA protocol is subject to many security threats that affect the robustness and reliability of the 5G network. On the other hand, blockchain is a new technology for decentralized applications.