## 1 Introduction  
Vehicle-to-Everything (V2X) communication [1] is the technology for connected vehicles to support road safety and prevent traffic accidents. V2X allows vehicles to broadcast periodic messages about the surrounding area. Recently, many technologies target road safety with high data rates to provide alerts about upcoming crashes. Multiple accessing technologies provide connectivity in vehicular networks, such as Wi-Fi, IEEE 802.11p, and cellular radio communications. Recently, Cellular-V2X (C-V2X) was standardized by the third-generation partnership project (3 GPP) for automotive services. LTE-V2X is the current 3 GPP Release 14 [2] standard that has many enhancements to provide the new 3 GPP Release 16 for the new 5G radio generation [3]. The majority of the shortcomings of DSRC, 802.11p, and LTE-V2X are meant to be handled through the efficient function handlers in 5G-V2X. Proposing efficient light-weight security solutions against known and unknown threats depends on the deployment strategies of 5G-V2X. The deployment of 5G Base Stations (BSs) defines the exploitation of possible network vulnerabilities. Moreover, key exposure and the insecure communication channel were considered as points of attack in 5G-V2X. Due to the high mobility conditions, attack possibilities are increasing. Optimizing the 5G-NR in V2X communication has high requirements and efficient light-weight security methods to support many V2X services and applications [4]. The 5G NewRadio (NR) was developed to enhance the network scalability, flexibility, and efficiency of the spectrum and power usage [5]. V2X communication offers different benefits, but it creates many privacy and security concerns [6]. Many proposed security protocols are trying to satisfy the security standards requirements and challenges [7]. V2X authentication and privacy are the most critical issues that are our basic concerns in this study. A few studies looked at the security requirements of C-V2X networks [8; 9]. C-V2X security standards in the 3 GPP Release 15 and beyond are based on the Public Key Infrastructure (PKI), to preserve privacy and support message authentication. PKI-based solutions suffer high communication and computation overhead due to the large size of the attached certificate and signature [10]. 5G-V2X infrastructure plays a vital role in designing efficient security protocol. The intensive deployment of 5G BSs at short distances can serve as Road Side Units (RSUs) to offer security services for road vehicles [11]. Each vehicle authenticates itself to the joined cell BS before communication. The handover authentication between BSs consumes long delays to transfer the authentication parameters of vehicles between different cells. Moreover, in 3 GPP Release 15, LTE-V2X supports 100 ms End-to-End latency that can allow vehicles to communicate with BSs, request the authentication parameters, and authenticate messages within this time. However, in Release 16, for the 5G-V2X it was assumed that latency was 5 ms or less, which required fast authentication procedures to satisfy the 5G requirements. One enhancement introduced by the 5 GCAR project was related to the concept of zones as a solution to provide common local services using BSs as roadside units (RSUs). As considered in 5 GCAR, the BSs were grouped to form smart radio access service areas, referred to as Smart Zones (SM-Zones) [12]. In this study, we assumed that the 5G-V2X network is divided into \(N\) zones, and every zone is covered by \(n\) BSs. For a single zone, all vehicles were configured with common security parameters to securely communicate without high-cost re-authentication, when they moved from one BS to another. We propose a Multi-Zone Authentication and Privacy-Preserving Protocol (MAPP), based on the bilinear pairing cryptography and a short digital signature. The proposed protocol supports the message and identity authentication within single-zone and multiple zones that enhance the 5G-V2X network security and availability.