1. Bibliographic Information

1.1. Title

5G Vehicle-to-Everything Services: Gearing Up for Security and Privacy

1.2. Authors

The authors of this paper are:

• Rongxing Lu (Senior Member, IEEE) from the Faculty of Computer Science (FCS), University of New Brunswick (UNB), Fredericton, NB, Canada.

• Lan Zhang (Student Member, IEEE) from the Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL, USA.

• Jianbing Ni (Member, IEEE) from the Department of Electrical and Computer Engineering, Queen's University, Kingston, ON, Canada.

• Yuguang Fang (Fellow, IEEE) from the Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL, USA.

  Their affiliations suggest expertise in computer science, electrical and computer engineering, with strong backgrounds in networking, security, and wireless communications, which are directly relevant to the paper's topic.

1.3. Journal/Conference

This article has been accepted for inclusion in a future issue of an IEEE journal. Given the authors' affiliations and the technical nature of the content, it is likely an IEEE Transactions or IEEE Magazine publication, which are highly reputable venues in the fields of telecommunications, networking, and computer science.

1.4. Publication Year

The paper was published at (UTC): 2019-11-13T00:00:00.000Z, so the publication year is 2019.

1.5. Abstract

The abstract introduces 5G as a platform for Vehicle-to-Everything (V2X) services, supporting networking connections for sensors and vehicles on roads, benefiting drivers and pedestrians with improved safety, high reliability, large communication coverage, and low service latency. However, it also highlights the serious trust, security, and privacy issues arising from ubiquitous network connectivity, which could hinder 5G V2X's success. The article presents a comprehensive survey on the security of 5G V2X services. It reviews the architecture and use cases, examines trust, security, and privacy issues, discusses potential attacks, and analyzes state-of-the-art strategies to achieve protection in each area. Finally, it suggests future research directions to encourage further attention and effort in 5G V2X services.

1.6. Original Source Link

The original source link is /files/papers/6913e9e31c90891eaa5cfa20/paper.pdf. The publication status is "accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination." This indicates it's a peer-reviewed, accepted version, likely a preprint or an "early access" version before final journal pagination.

2. Executive Summary

2.1. Background & Motivation

The core problem this paper aims to solve is the critical need for robust security, privacy, and trust mechanisms within the rapidly emerging 5G Vehicle-to-Everything (V2X) ecosystem. 5G V2X communication promises transformative benefits, including enhanced road safety, higher communication reliability, extensive coverage, and minimal service latency, by enabling vehicles, infrastructure, pedestrians, and network entities to exchange information seamlessly.

However, this pervasive connectivity introduces significant vulnerabilities. The paper highlights that wireless interfaces in vehicles create new attack surfaces, making them susceptible to remote access by malicious actors, as demonstrated by past incidents like the remote hacking of a Jeep. As vehicles become "data centers on wheels," carrying sensitive information like GPS data and V2X service data, the potential for data exposure and corruption becomes a major concern for drivers and network operators alike. The network infrastructure of 5G itself is also vulnerable to various cyberattacks. Without adequate trust, security, and privacy safeguards, the success and widespread adoption of 5G V2X services could be severely impeded, as users will be hesitant to adopt technologies they do not perceive as safe and reliable. The paper's entry point is to provide a comprehensive, structured overview of these multi-faceted challenges and the current state of solutions.

2.2. Main Contributions / Findings

The paper makes several primary contributions by providing a comprehensive survey on the security of 5G V2X services:

• Comprehensive Overview of 5G V2X: It begins by presenting a structured review of the architecture, communication types (e.g., V2V, V2I, V2P, V2N), and various use cases (e.g., Cooperative Awareness, Teleoperated Driving) of 5G V2X systems. This provides a foundational understanding for analyzing security aspects.

• Identification of Key Challenges (Trust, Security, Privacy Issues and Attacks): The paper systematically identifies and categorizes the trust, security, and privacy issues inherent in 5G V2X services. It details potential attacks across all layers of the 5G V2X architecture, ranging from well-known cyberattacks (e.g., DoS, MITM, eavesdropping) to specific V2X-oriented threats (e.g., inference attacks, identity revealing attacks). This structured threat model is crucial for understanding the attack landscape.

• Analysis of State-of-the-Art Protection Strategies: It offers an in-depth analysis of existing strategies and solutions to address the identified trust, security, and privacy challenges. The solutions are elaborated upon within the context of each layer of the 5G V2X architecture, demonstrating how different protective mechanisms work to achieve their respective goals (e.g., certificate-based trust, encryption, pseudonymity, differential privacy).

• Identification of Future Research Directions: The article concludes by pointing out several open problems and promising future research directions, such as secure network caching, security-enhanced network slicing, privacy-preserving network data analytics, and secure autonomy functions. These directions are intended to stimulate further research and development in the field.

  The paper's key conclusion is that while 5G V2X offers immense benefits, its widespread adoption hinges on effectively addressing the complex trust, security, and privacy concerns. The findings highlight the multi-layered nature of these challenges and the need for a holistic approach involving various cryptographic, architectural, and procedural strategies to build a trustworthy and resilient 5G V2X ecosystem.

3. Prerequisite Knowledge & Related Work

3.1. Foundational Concepts

To understand this paper, a reader should be familiar with several foundational concepts related to wireless communication, networking, cybersecurity, and vehicular systems:

• Vehicle-to-Everything (V2X) Communication: This is a general term referring to the communication of information from a vehicle to any other entity that may affect the vehicle, and vice versa. It encompasses several specific communication modes:
  • Vehicle-to-Vehicle (V2V): Direct communication between vehicles, often used for immediate safety applications like collision avoidance.
  • Vehicle-to-Infrastructure (V2I): Communication between vehicles and roadside infrastructure (e.g., Roadside Units or RSUs) for traffic management, signal timing, or data exchange.
  • Vehicle-to-Pedestrian (V2P): Communication between vehicles and pedestrians (e.g., via their smartphones or dedicated devices) to alert both parties of potential hazards.
  • Vehicle-to-Network (V2N): Communication between vehicles and a cellular network or remote servers, enabling services like real-time traffic updates, cloud services, and teleoperated driving.
• 5G (Fifth Generation Wireless Technology): The latest generation of cellular technology, designed to deliver higher multi-Gbps peak data speeds, ultra-low latency, massive capacity, increased availability, and a more uniform user experience to more users. Key characteristics relevant to V2X include:
  • High Data Rate: Enables rapid exchange of large amounts of data (e.g., video, high-definition maps).
  • Massive Device Connectivity: Supports a vast number of connected devices simultaneously, essential for a dense V2X environment.
  • Low Service Latency: Crucial for safety-critical applications requiring real-time responses.
  • 5G New Radio (NR): The new air interface developed for 5G, providing improved flexibility, scalability, and efficiency.
• Networking Technologies within 5G:
  • Software-Defined Networking (SDN): An architecture that decouples the network control plane from the data forwarding plane, allowing network behavior to be centrally managed and programmed. This offers flexibility and simplified network management.
  • Network Function Virtualization (NFV): A concept that virtualizes network services (e.g., firewalls, load balancers, routing) that traditionally run on proprietary hardware, allowing them to run as software on standard servers. This increases agility and reduces costs.
  • Network Slicing: A key 5G feature that allows multiple virtual networks to run on top of a shared physical infrastructure. Each slice can be customized to meet specific service requirements (e.g., a safety-critical V2X slice might prioritize ultra-low latency and high reliability).
  • Mobile Edge Computing (MEC) / Multi-access Edge Computing: An architecture that brings computing and storage resources closer to the data sources (e.g., vehicles, IoT devices) at the edge of the network. This reduces latency, saves bandwidth, and enables real-time processing for V2X applications.
• Core Security Requirements (CIA Triad + Availability):
  • Confidentiality: Ensuring that information is accessible only to those authorized to have access. Preventing eavesdropping.
  • Integrity: Ensuring the accuracy and completeness of data. Preventing unauthorized modification or fabrication of messages.
  • Authenticity: Verifying the identity of users, devices, or data sources. Ensuring that a message or entity is genuinely who or what it claims to be.
  • Availability: Ensuring that authorized users have continuous and uninterrupted access to services and resources. Preventing Denial-of-Service (DoS) attacks.
• Trust Management: A framework for evaluating, establishing, and maintaining trust relationships between entities in a system. It often involves trust authorities (TAs), certificates, and reputation systems.
• Privacy: The right of individuals to control access to their personal information. In V2X, this includes identity privacy, location privacy, content privacy, and contextual privacy.

3.2. Previous Works

The paper explicitly differentiates itself from existing surveys that primarily focus on specific aspects of 5G V2X. It mentions:

• Surveys reviewing communication techniques in 5G V2X (e.g., [8], [9]). These would typically delve into the technical details of radio access technologies, protocols, and network architectures for enabling V2X connectivity.

• Surveys overviewing authentication or privacy preservation mechanisms in 5G V2X (e.g., [7], [10], [11]). These might focus on specific cryptographic primitives, authentication protocols, or pseudonymity schemes without covering the broader trust and security landscape across all 5G V2X layers.

  This paper distinguishes itself by offering a comprehensive survey focused specifically on the trust, security, and privacy threats and potential strategies across the entire 5G V2X ecosystem, analyzed layer by layer. It aims to provide a holistic view of the vulnerabilities and defense mechanisms, rather than a deep dive into communication protocols or a single security aspect.

3.3. Technological Evolution

The paper places its work within the context of V2X technology evolving from LTE and LTE-advanced towards 5G. LTE and LTE-advanced initially provided flexible and cost-effective solutions for early V2X communications, often augmented with Multi-access Edge Computing (MEC). The transition to 5G is driven by its ability to support more demanding V2X use cases due to its superior capabilities in data rate, device connectivity, and latency.

The architectural evolution is also highlighted by the integration of advanced networking techniques like Software-Defined Networking (SDN), Network Function Virtualization (NFV), and network slicing into the 5G core and edge networks. These technologies fundamentally change how networks are built and managed, offering new flexibilities but also introducing new security challenges. For example, network slicing can isolate different V2X services, improving resilience, but also presents unauthorized access risks. 5G New Radio (NR) represents the radio access technology evolution, providing significant enhancements over previous generations.

3.4. Differentiation Analysis

Compared to prior research, this paper's core innovation lies in its comprehensive and layered approach to trust, security, and privacy specifically within 5G V2X services. While other surveys might cover individual aspects like communication protocols or specific authentication mechanisms, this paper:

• Holistic Scope: Examines the interconnected challenges of trust, security, and privacy together, recognizing their interdependencies.

• Layered Analysis: Systematically breaks down the issues and solutions across the entire 5G V2X architecture: 5G access network, network edge, 5G core network, and data network. This provides a granular understanding of vulnerabilities and defenses at each operational level.

• Threat and Strategy Mapping: Directly maps identified trust, security, and privacy issues and associated attacks to existing and potential defense strategies, offering a structured roadmap for addressing these concerns.

• Future-Oriented: Beyond current solutions, it explicitly identifies open problems and future research directions tailored to the unique characteristics of 5G V2X.

  This structured, comprehensive, and forward-looking analysis of trust, security, and privacy threats and countermeasures across the 5G V2X stack is what differentiates this paper from more narrowly focused existing surveys.

4. Methodology

4.1. Principles

As a survey paper, the core methodological principle is to provide a comprehensive and structured overview of the trust, security, and privacy landscape within 5G V2X services. The authors adopt a top-down, layered approach to analyze the 5G V2X architecture, systematically identifying challenges and potential solutions at each layer. The intuition is that 5G V2X is a complex, multi-layered system, and a holistic understanding of its security, privacy, and trust implications requires examining each component and its interactions.

The paper aims to:

1. Establish Context: Provide an overview of 5G V2X architecture, communication types, and use cases.
2. Identify Challenges: Detail specific trust, security, and privacy issues and associated attack vectors for each layer.
3. Survey Solutions: Present state-of-the-art strategies to mitigate these challenges, again categorizing them by architectural layer and problem type.
4. Highlight Future Work: Pinpoint current gaps and promising directions for future research.

4.2. Core Methodology In-depth (Layer by Layer)

The paper's methodology involves dissecting 5G V2X services across its architectural layers and then systematically analyzing trust, security, and privacy aspects.

4.2.1. 5G V2X Overview (Section II)

The paper begins by establishing a foundational understanding of 5G V2X.

4.2.1.1. 5G V2X Architecture

The authors describe the 5G V2X architecture as consisting of four network layers, referencing 3GPP standards (TS 23.501, TR 23.886, TS 23.287).

The following figure (Figure 1 from the original paper) illustrates the multi-layered architecture of 5G V2X services:

Figure 1. Architecture of 5G V2x services.

• 5G Access Network: This layer comprises the Next-Generation Radio Access Network (NG-RAN) and/or non-3GPP access networks. It connects User Equipment (UE) (such as vehicles, infrastructure, sensors, and mobile phones) to the 5G Core Network. 5G V2X communications operate in two modes: PC5 (direct communication, proximity-based service discovery) and LTE-Uu (cellular network communication). 5G NR is a key component for radio enhancements.
• Network Edge: Situated between the 5G Access Network and the 5G Core Network, the network edge hosts edge servers. These servers deploy computing and storage resources, along with virtual network functions (VNFs), to support delay-sensitive or location-aware V2X services (e.g., road surface ice detection, video and map sharing, vehicle platooning). Resources are virtualized into Virtual Machines (VMs) and managed by local controllers. The access network is divided into network slices for different V2X services. Non-3GPP access networks connect to the 5G Core Network via a non-3GPP Interworking Function (N3iWF), secured by IPSec tunnels.
• 5G Core Network: This layer is designed for mobile data connectivity and services, leveraging SDN and NFV. It separates the User Plane Function (UPF) from the Control Plane Function (CPF).
  • UPF handles traffic usage reporting, data forwarding, and transport-level packet marking.
  • CPF manages packet processing in UPF through rules and sessions. Key CPF functions (virtualized) include:
    • Authentication Server Function (AUSF): Supports authentication for 3GPP and untrusted non-3GPP access.
    • Access and Mobility Management Function (AMF): Manages UE registration, access authentication, and authorization.
    • Session Management Function (SMF): Handles session management, IP address management, and UP selection/control.
    • Network Slice Selection Function (NSSF): Selects network slice instances and determines Network Slice Selection Association Information (NSSAI).
    • Unified Data Management (UDM): Generates primary authentication credentials and manages user identification/subscription.
    • Network Data Analytics Function (NWDAF): Provides slice-specific network data analytics.
    • Security Edge Protection Proxy (SEPP): A non-transparent proxy for inter-PLMN message filtering, policing, key management, mutual authentication, and cipher suite negotiation for roaming UEs.
  • Security solutions in the 5G Core include primary authentication and key agreement based on EAP-AKA, key hierarchy generation, Internet Key Exchange (IKE) for non-3GPP access, IPSec Encapsulating Security Payload (ESP), and TLS for service-based interfaces.
• Data Network: This external network (e.g., the Internet) connects to the 5G Core Network to offer various V2X services (e.g., remote driving, autonomous driving, dynamic ride sharing). V2X servers often use edge resources for computation offloading and data caching to reduce latency.

4.2.1.2. Types of 5G V2X Communications

The paper classifies 5G V2X communications into two main categories:

• Device-to-Device (D2D) Communications:
  • V2V (Vehicle-to-Vehicle): Direct communication between vehicles for safety (e.g., collision avoidance), requiring low latency and high reliability.
  • V2I (Vehicle-to-Infrastructure): Communication between a vehicle and a Roadside Unit (RSU) for exchanging delay-insensitive information (e.g., traffic data, information services). Features short-lived, high data rate connections.
  • V2P (Vehicle-to-Pedestrian): Direct communication between vehicles and pedestrians to exchange position, speed, and direction for collision prediction and alerts.
• Device-to-Network Communications:
  • V2N (Vehicle-to-Network): Communication between vehicles and remote servers for various services (e.g., real-time traffic, weather, customized navigation).

4.2.1.3. Use Cases of 5G V2X

The paper outlines six categories of 5G V2X use cases, based on [2]:

• Cooperative Awareness: Providing vehicles with information about their surroundings (e.g., emergency vehicle warning, forward collision warning).
• Cooperative Sensing: Exchanging sensor data among vehicles to improve environmental perception (e.g., for cooperative autonomous driving).
• Cooperative Maneuvering: Enabling groups of autonomous vehicles to drive coordinately (e.g., cooperative collision avoidance, vehicle platooning).
• Awareness of Vulnerable Road Users (VRUs): Detecting and alerting drivers/pedestrians about VRUs (e.g., pedestrians, cyclists) using V2P communications.
• Improving Traffic Efficiency: Using V2I and V2N for services like customized navigation and traffic management.
• Teleoperated Driving: Remotely controlling a vehicle via V2N communications, often seen as a transitional solution towards full autonomy.

4.2.2. Key Challenges in Secure 5G V2X Services (Section III)

This section systematically identifies trust, security, and privacy issues and relevant attacks across the 5G V2X ecosystem.

4.2.2.1. Trust Issues in 5G V2X Services: Issues and Attacks

• Issues: Ubiquitous network connectivity expands the attack surface. Concerns arise from design flaws, misconfiguration, implementation bugs, and dishonest entities with personal incentives. The reliability of 5G systems and V2X services is at high risk. Trust management is crucial, involving Trust Authorities (TAs) for certificate management. The fluid roles of entities in V2X (e.g., a vehicle acting as both user and server) make trust management complex.
• Attacks:
  • Bad Mouth Attacks: Malicious entities provide dishonest recommendations to frame good entities or boost malicious ones.
  • Conflicting Behavior Attacks: Malicious entities act inconsistently over time or towards different groups to hide their identity and cause damage (e.g., on-off attacks).
  • Blackhole Attacks: A type of DoS attack where a malicious entity discards packets that should be relayed, potentially advertising false fresh routes in multihop routing.
  • Sybil Attacks: A malicious entity forges multiple fake identities to evade blame or manipulate the system.

4.2.2.2. Security Issues in 5G V2X Services: Issues and Attacks

• Issues: 5G V2X increases attack surfaces. Basic security requirements:
  • Confidentiality: Preventing unauthorized disclosure of information.
  • Authenticity: Confirming the true identity of an entity.
  • Integrity: Ensuring accuracy and reliability of transmitted information against falsification.
  • Availability: Ensuring authorized users can always access V2X services, with violations leading to DoS.
• Attacks:
  • Attacks in V2X Communications:
    • Eavesdropping: Passive listening to wireless messages. Even encrypted messages can reveal source and destination.
    • Message Forgery: Fabricating bogus V2X messages to mislead (e.g., false warnings).
    • Jamming: Maliciously consuming spectrum resources by sending misleading messages, disrupting normal V2X communications.
    • Impersonation: Attacker uses a false identity, requiring credentials of legitimate entities.
    • Replay Attacks: Resending previously broadcast V2X messages to disrupt traffic flow.
    • MITM (Man-in-the-Middle) Attacks: Attacker intercepts and relays communication between two entities, sniffing and potentially altering information.
    • Sybil Attacks: Attacker generates multiple identities to send different messages, misleading recipients.
  • Attacks on Network Edge:
    • Location Spoofing: Attacker falsifies location to gain unauthorized access to location-based services.
    • DoS Attacks: Overwhelming resource-limited edge servers to make services unavailable.
    • Fake Attacks: Adversary fakes an edge server (e.g., base station) to attract victims and expose sensitive information.
  • Attacks on 5G Core Networks:
    • Hijacking Attacks: Exploiting SDN vulnerabilities to hijack host locations, overloading controllers and paralyzing V2X services.
    • Saturation Attacks: Inundating OpenFlow controllers with flow requests to exploit scalability issues between data and control planes, making V2X services unavailable.
    • Link Fabrication Attacks: Injecting fake LLDP (Link Layer Discovery Protocol) packets between OpenFlow switches to create non-existent links, causing DoS.
    • Unauthorized Slice Accesses: Attacker consumes resources of a network slice without proper authentication, leading to DoS for legitimate services, or uses access to one slice to attack others if isolation is poor.
  • Attacks on Data Network/Internet:
    • DoS Attacks: Compromised V2X internal entities (e.g., vehicles) launch DoS attacks on the data network, degrading 5G V2X service performance.
    • Malware Injection: Exploiting vulnerabilities in cloud computing operations (e.g., outdated tools) to inject malware to control cloud servers and affect V2X users.

4.2.2.3. Privacy Issues in 5G V2X Services: Issues and Attacks

• Issues: Pervasive 5G V2X services raise concerns about user control over privacy.
  • Identity Privacy: Disclosure of identifiable information (e.g., name, license number, IMSI).
  • Content Privacy: Disclosure of sensitive information within disclosed content (documents, videos, images).
  • Contextual Privacy: Attacker links source and destination of a packet, inferring service usage.
  • Location Privacy: Adversary controls/accesses current and past locations of a user.
• Attacks: Beyond traditional eavesdropping, MITM, impersonation:
  • Packet Analysis Attacks: Adversary identifies sender's identity by analyzing packet content (e.g., source inference).
  • Packet Tracing Attacks: Adversary eavesdrops to trace source and destination without recovering content.
  • Linkage Attacks (Correlation Attacks): Attacker links pseudonyms of a user based on public information (e.g., reputation, locations) to infer trajectory.
  • Movement Tracking Attacks: Tracing a vehicle's physical positions and moving patterns by analyzing captured messages.
  • Identity Revealing Attacks: Collecting sensitive information to predict identity, moving path, physical position.
  • Collusion Attacks: Adversaries collaborate to learn more about a target user.
  • Inference Attacks: Gaining knowledge about a subject by recognizing differences among multiple subjects from large collected data.
  • Deanonymization/Reidentification Attacks: Re-identifying owners of anonymized data by analyzing correlations.

4.2.3. Key Strategies to Secure 5G V2X Services (Section IV)

This section surveys existing strategies to address the identified issues, categorized by layer.

4.2.3.1. Trust Management Strategies in 5G V2X Services

• Data Networks/Internet:
  • Certificate-based strategies: X.509 standard, Certificate Authority (CA), Certificate Revocation List (CRL).
  • Social network strategies: Centralized or distributed trust relationships (e.g., DSRC), recommendation/reputation-based trust scores, reevaluation and reputation fading mechanisms to combat bad mouth and conflicting behavior attacks. Entropy for trust uncertainty.
• 5G Core Networks:
  • Strong cryptographic primitives: Authentication protocols (5G AKA, EAP framework), key generation functions, use of certificates, preshared keys, token cards.
  • SDN/NFV technologies: Network slicing to isolate V2X services with different trust requirements, improving resilience.
• Network Edge:
  • Authentication strategies: Trusted certificates for edge servers and users in each trust domain. Consideration of factors like geographical location and resource ownership.
  • Distributed trust evaluation: Blockchain for trust evaluation and secure handover between edge nodes, removing reliance on a central party.
• V2X Communications:
  • Combination of infrastructure-based centralized strategies (e.g., certificate-based) and self-organizing social network strategies (for V2V, V2P).
  • Holistic evaluation of trustworthiness based on an entity's different roles.
  • Reuse of public key and certificate infrastructure when shifting between 5G V2X and DSRC.
  • Continuous trust management adapted from 3GPP generations, centralizing security-sensitive functions for efficient handovers.

4.2.3.2. Security Strategies in 5G V2X Services

• Data Networks/Internet:
  • DoS Attacks: Prevention (anomaly/signature detection, filtering devices, resource absorption), Detection (rate-based, anomaly detection, machine learning), Post-attack (traceback, response mechanisms).
  • Malware Injection: Malware detection techniques (enhanced functionality, machine learning algorithms, online forensics).
• 5G Core Networks:
  • Topology Poisoning Attacks (Hijacking, Link Fabrication): TopoGuard (security extension for OpenFlow controllers) employs port manager, host prober, and topology update checker.
  • Saturation Attacks: AvantGuard (extension for OpenFlow networks) uses connection migration (data plane proxies TCP handshake, SYN cookies) and flow rule triggers.
• Network Edge:
  • Location Spoofing Attacks: Location proof mechanisms (e.g., distance-bounding protocols like Brands and Chaum's, verifiable multilateration schemes) and detection algorithms (analyzing forged locations).
• V2X Communications:
  • Eavesdropping Attacks: Encryption, anonymous communication techniques (e.g., onion routing), friendly jamming (introducing noise for eavesdroppers).
  • Message Forgery Attacks: Data integrity verification (Reed-Solomon code, checksums, trapdoor hash functions, MAC, digital signatures), traceability feature for internal attackers.
  • Jamming Attacks: Physical layer frequency hopping, direct sequence spread spectrum, jamming attack detectors (e.g., for CSMA-CA networks).
  • Impersonation Attacks: Authentication and digital signatures for all messages, TA usage, variable MAC and IP addresses.
  • Replay Attacks: Globally synchronized time or nonce (timestamp) attached to messages.
  • MITM Attacks: Enhanced Diffie-Hellman (DH) schemes, multiway challenge-response protocols (e.g., Needham-Schroeder, Kerberos).
  • Sybil Attacks: Threat detection protocols (privacy-preserving detection of abuses of pseudonyms, session key certificates, enhanced packet detection algorithms), cryptographic techniques (e.g., encryption with identity).

4.2.3.3. Privacy Strategies in 5G V2X Services

• Data Networks/Internet:
  • Anonymous credentials: Blind signatures (signer doesn't see message, perfect privacy), group signatures (anonymous within group, group manager can reveal signer), pseudonyms (temporary identities validated by CA or TA).
  • Other techniques: Cryptographic accumulators, spatial and temporal cloaking, mixed networks.
• 5G Core Networks:
  • Pseudonyms: Assigned by network operators, used for identifier privacy, generated by network operator for traceability, non-reproduction, non-frameability.
  • Anonymization: AnonyFlow (SDN-based service assigning temporary IP addresses and disposable flow-based identifiers).
  • Host protection: Virtual IP addresses for network hosts, translated by OpenFlow switches.
• Network Edge:
  • Cryptography-based schemes and pseudonym-based schemes for mobile fog/edge computing.
  • Secure profile matching for network slice selection (e.g., anonymous credentials with profile matching for 5G IoT services).
  • Differential Privacy: Adding mathematical noise to location data to protect individual privacy while allowing statistical analysis (e.g., Laplace perturbation, exponential perturbation).
• V2X Communications:
  • Mix-Zone Approaches: Using mix networks (chain of proxy servers) and mix zones (areas for pseudonym changing) to prevent tracking (MixGroup, cryptographic mix zone).
  • Group-Oriented Techniques: Hiding users in large groups.
    • Group signature: Conditional privacy (real identity revealed if misbehavior detected), addressing identity revocation management.
    • Ring signature: Vehicle's message hidden among neighboring vehicles, supporting anonymous message authentication.
  • Pseudonym-Based Approaches: Public key cryptography (randomizing certificates) or symmetric cryptography (random pseudoidentities).
    • Security Credential Management System (SCMS): RA and PCA collaboratively issue pseudonym certificates without linking them to specific vehicles (unless colluding).
    • Identity-based cryptography: TA or KGC issue pseudonyms.
    • Decentralized pseudonym issuance: Roadside infrastructures issue pseudonyms, or threshold-based secret sharing for $n$ authorities to reveal identity with $k$ out of $n$.

5. Experimental Setup

This paper is a comprehensive survey and literature review. As such, it does not present original experimental work, datasets, evaluation metrics, or baseline comparisons in the traditional sense of empirical research. Its "setup" is the structured collection and analysis of existing knowledge. Therefore, there are no specific datasets used, evaluation metrics defined, or baseline models compared within this paper's methodology. The authors' "results" are the summarized findings from the vast body of literature they review.

6. Results & Analysis

As this is a survey paper, it does not present new experimental results or conduct ablation studies. Instead, its "results" are the systematic synthesis and analysis of existing research findings concerning trust, security, and privacy in 5G V2X services.

6.1. Core Results Analysis

The paper's core analysis is presented through the comprehensive categorization of issues and solutions across the 5G V2X architecture.

Key Analytical Findings:

• Multi-layered Vulnerability: The 5G V2X ecosystem is vulnerable at every layer: access network, edge, core, and data network, as well as during V2X communications themselves. Each layer introduces specific attack vectors due to its unique functionalities and underlying technologies (e.g., SDN/NFV in the core, location-based services at the edge, wireless broadcast in V2X communications).
• Interconnected Challenges: Trust, security, and privacy are deeply intertwined. For instance, a lack of trust management can lead to Sybil attacks, which in turn compromise authenticity and data integrity. Location privacy breaches are often a result of eavesdropping or movement tracking attacks.
• Diversity of Attacks: The paper demonstrates that 5G V2X is susceptible to a broad spectrum of attacks, from traditional cyberattacks (DoS, MITM, malware) to those specific to vehicular networks (message forgery, jamming, location spoofing) and advanced privacy attacks (linkage, deanonymization).
• Layer-Specific Solutions are Essential: No single solution can address all trust, security, and privacy challenges. The survey highlights that effective protection requires a combination of strategies tailored to each architectural layer and communication type. For example, cryptographic primitives and network slicing are crucial in the 5G core, while anonymous credentials and differential privacy are vital for privacy at the data network and edge, respectively.
• Complexity of Trust Management: The dynamic and multifaceted roles of entities in V2X (e.g., a vehicle can be both a client and a server) make trust management particularly challenging, requiring sophisticated reputation systems and certificate management beyond basic authentication. Blockchain is identified as a promising technology for distributed trust.
• Conditional Privacy is a Trade-off: Many privacy-preserving schemes, particularly those using pseudonyms or group signatures, offer conditional privacy. This means users are anonymous until misbehavior is detected, at which point their real identity can be revealed. This represents a necessary trade-off between absolute privacy and accountability.

Comparison with Baselines (Implicit in a Survey Context): While not comparing against specific baseline models, the paper implicitly compares the state-of-the-art solutions against the inherent vulnerabilities of 5G V2X. The "advantage" of the proposed strategies is their ability to mitigate the identified threats, while "disadvantages" or "limitations" are often highlighted as open problems or areas for future research (e.g., the computational overhead of complex cryptographic operations, the difficulty of managing revocations in pseudonym schemes).

The strength of the paper's analysis lies in its ability to synthesize a vast amount of prior research into a coherent framework, providing a clear map of the problem domain and the current arsenal of defense mechanisms.

6.2. Data Presentation (Tables)

This paper is a survey and does not contain experimental results presented in tables within its main body. Its findings are presented through descriptive text and a conceptual architecture diagram.

6.3. Ablation Studies / Parameter Analysis

As a survey paper, this article does not include ablation studies or parameter analyses, as these are typically conducted in empirical research to evaluate the components or hyper-parameters of a novel proposed model or algorithm. The paper's contribution lies in synthesizing existing knowledge rather than proposing and evaluating a new system.

7. Conclusion & Reflections

7.1. Conclusion Summary

This paper provides a timely and comprehensive survey of the trust, security, and privacy challenges facing 5G Vehicle-to-Everything (V2X) services. It effectively maps these concerns across the layered architecture of 5G V2X, from the access network to the data network. The authors meticulously detail a wide array of potential attacks, distinguishing between general cyberattacks and those specific to the V2X environment. Crucially, the paper then systematically presents existing state-of-the-art strategies and solutions designed to enhance trust, ensure security, and preserve privacy at each architectural layer. The overarching conclusion is that while 5G V2X promises significant societal benefits, its successful deployment is contingent upon robust, multi-layered defensive mechanisms that address the complex and interconnected issues of trust, security, and privacy.

7.2. Limitations & Future Work

The authors themselves identify several open problems and future research directions, highlighting areas where current solutions are either insufficient or nascent:

• Secure Network Caching at Network Edge: This involves addressing where and when to cache data, how to select trustworthy edge devices, and ensuring data confidentiality if edge nodes are compromised. This requires research into cache placement strategies, data replacement approaches, and secure data retrieval schemes.
• Security-Enhanced Network Slicing: Focuses on improving access authentication and authorization for specific network slices to prevent unauthorized access and resource consumption. Challenges include generating and managing authentication identifiers and keys with backward and forward security from 3GPP SUP1, and achieving efficient authentication for low-latency V2X services. Privacy concerns related to NSSAI disclosure are also noted.
• Privacy-Preserving Network Data Analytics: This is crucial given that the NWDAF (Network Data Analytics Function) collects sensitive location and behavioral data from vehicles. Future work needs to explore efficient and privacy-preserving mechanisms to prevent adversaries from inferring mobility patterns while still enabling valuable data analytics.
• Secure Autonomy Functions for Automated Vehicles: This addresses the need to protect every critical procedure in automated driving (data collection, exchange, analytics, decision-making, command control) against hackers. The paper stresses that while secure 5G V2X communications provide data reliability, they don't guarantee decision correctness or control security. Research is needed on verifiable data analytics (to identify miscalculations in machine learning) and building security protection mechanisms directly on vehicles (e.g., firewalls, intrusion detection systems).

7.3. Personal Insights & Critique

This paper serves as an excellent, foundational resource for anyone venturing into the intersection of 5G, V2X, and cybersecurity. Its layered approach to dissecting challenges and solutions is particularly insightful, underscoring the complexity and the need for a holistic security framework rather than isolated patches.

Inspirations: The paper strongly emphasizes that trust is not merely a byproduct of security and privacy, but a distinct and equally critical component, especially in V2X where dynamic roles and human factors (drivers, pedestrians) are involved. The discussion on trust management strategies like recommendation/reputation-based systems and the potential of blockchain is particularly inspiring for building robust, decentralized trust models. Furthermore, the detailed enumeration of privacy attacks and their countermeasures (e.g., differential privacy, mix-zones, anonymous credentials) highlights the active research frontier in balancing utility and individual rights in highly connected environments. The focus on security-enhanced network slicing is also a powerful reminder that 5G's architectural innovations must be secured from their inception.

Potential Issues or Areas for Improvement:

• Real-world Deployment Complexity: While the paper surveys a wide range of theoretical and proposed solutions, it does not delve into the practical challenges and trade-offs of deploying these complex cryptographic and architectural solutions in real-world 5G V2X environments. Factors like computational overhead on resource-constrained UEs (vehicles, sensors), standardization efforts, regulatory compliance, and interoperability between different vendors' implementations could be explored more.
• Human Factor in Trust: The paper touches upon trust issues but could expand on the human factor. Driver behavior, acceptance of V2X warnings, and the psychological aspects of trusting autonomous systems are crucial for adoption and present unique security/privacy challenges (e.g., driver manipulation, social engineering).
• Quantitative Analysis: As a survey, it naturally lacks quantitative analysis. Future work building upon this foundation could involve benchmarking different security/privacy mechanisms in simulated 5G V2X environments to understand their performance, overhead, and effectiveness against various attack models.

Transferability to other domains: The layered security analysis framework presented in this paper is highly transferable. For instance, the methodology of identifying trust, security, and privacy issues and then surveying solutions across architectural layers could be applied to:

• Industrial IoT (IIoT): Analyzing security for connected factories or critical infrastructure.

• Smart Cities: Securing interconnected smart devices, sensors, and services across urban environments.

• Healthcare IoT: Addressing privacy and security for wearable health devices and remote patient monitoring systems.

• Drone Networks: Securing communication and control for autonomous drone operations.

  The paper provides an excellent blueprint for understanding and tackling complex cybersecurity challenges in any highly interconnected, critical infrastructure domain.