# A Blockchain-Assisted Security Protocol for Group Handover of MTC Devices in 5G Wireless Networks
###### Abstract  
In the realm of the fifth-generation (5G) wireless cellular networks, renowned for their dense connectivity, there lies a substantial facilitation of a myriad of Internet of Things (IoT) applications, which can be supported by the massive machine-type communication (MTC) technique, a fundamental communication framework. In some scenarios, a large number of machine-type communication devices (MTCD) may simultaneously enter the communication coverage of a target base station. However, the current handover mechanism specified by the 3 rd Generation Partnership Project (SGPP) Release 16 incurs high signaling overhead within the access and core networks, which may have negative impacts on network efficiency. Additionally, other existing solutions are vulnerable to malicious attacks such as Denial of Service (DoS), Distributed Denial of Service (DDoS) attacks, and the failure of Key Forward Secrecy (KFS). To address this challenge, this paper proposes an efficient and secure handover authentication protocol for a group of MTCDs supported by blockchain technology. This protocol leverages the decentralized nature of blockchain technology and combines it with certificateless aggregate signatures to mutually authenticate the identity of a base station and a group of MTCDs. This approach can reduce signaling overhead and avoid key escrow while significantly lowering the risk associated with single points of failure. Additionally, the protocol protects device anonymity by encrypting device identities with temporary anonymous identity markers with the Elliptic Curve Diffie-Hellman (ECDH) to abandon serial numbers to prevent linkage attacks. The resilience of the proposed protocol against predominant malicious attacks has been rigorously validated through the application of the BAN logic and Scyther tool, underscoring its robust security attributes. Furthermore, compared to the existing solutions, the proposed protocol significantly reduces the authentication cost for a group of MTCDs during handover, while ensuring security, demonstrating commendable efficiency. 202423312024233120242312024  
devices. Furthermore, adding more base stations can effectively alleviate traffic congestion in wireless channels. Therefore, the 5G wireless network is expected to significantly enhance the performance of wireless connectivity with higher transmission rates, lower communication latency, and greater network capacity. Considering the impending 5G wireless network evolution, a prominent challenge emerges concerning access authentication and data transmission for a vast array of IoT terminals [2]. If each IoT device persists in employing the Extensible Authentication Protocol-Authentication and Key Agreement (EAP-AKA) or the 5G Authentication and Key Agreement (5G-AKA) for its authentication, it would inevitably lead to a surge in signaling and communication overheads [3]. The 5G-AKA protocol is a new authentication and key agreement protocol standardized by the 3 rd Generation Partnership Project (3 GPP) to be used in the 5G wireless networks. The 5G-AKA protocol plays a pivotal role in enhancing 5G wireless network security by enabling mutual authentication between base stations, core networks, and user devices, thus overcoming the vulnerabilities identified in the 4G wireless networks. It introduces the Subscription Concealed Identifier (SUCI), leveraging encryption to safeguard the sensitive information of users like International Mobile Subscriber Identification (IMSI), against unauthorized interception and malicious base station attacks. This approach significantly bolsters personal privacy and network security, ensuring wireless communications are secure and confidential. Notably, the existing 5G standard, as outlined in the 3 GPP standard, exhibits challenges when dealing with concurrent handovers of a cluster of MTCDs. Recent studies [4] have highlighted security loopholes within the handover authentication procedure.