Contents Introduction
The oncoming emergence of sixth-generation (6G) communication technology is poised to revolutionize the ways we interact with nearly everything around us. This technology promises seamless and massive connectivity that is expected to enable everything from autonomous vehicles to smart cities and beyond. At present, vehicles, which are increasingly linked to human mobility, must achieve several technological advancements to keep up with the demands of 6G communication [1].
In particular, 6G has the potential to revolutionize Vehicle-to-Everything (V2X) communication, which comprises various concepts including Connected Autonomous Vehicles (CAVs), Internet of Vehicles (IoV), Intra-vehicular communication, and Vehicle-to-Vehicles (V2V) communication. These advancements are modernizing transportation by facilitating safer and more efficient transportation [2]. V2X communication allows for the exchange of data between a vehicle and other entities in its environment, including other vehicles, infrastructure, and even pedestrians. V2X communication is designed to enhance the safety and efficiency of transportation systems by allowing vehicles to communicate with both each other and their surroundings in real-time [3]. V2X communication is primarily dependent on wireless communication technologies such as Dedicated Short-Range Communications (DSRC) based on Road Side Units (RSUs), WiFi, and mobile network communication. These technologies involve vehicles exchanging data with each other as well as with infrastructure over short and long distances, respectively.
V2X communication is considered to be a technological candidate that can potentially play a significant role in the development of autonomous vehicles and smart transportation systems, as it can provide vehicles with the information they need to operate safely and efficiently in complex environments [10].
Several renowned companies are currently pursuing autonomous vehicle projects, which involve the extensive utilization of communication technologies. The automotive industry is currently experiencing significant technological advancements with a shared innovative objective of creating intelligent and self-driving cars. These types of vehicles can be categorized as either Automotive Vehicles or Connected Vehicles. In the United States, the term Connected Vehicles (CVs) is used for communication between cars [11], while in EU countries, systems operating on the V2X concept are referred to as Cooperative Intelligent Transport Systems (C-ITS) [12]. Table 1 briefly describes the scope of the most prominent industrial works based on V2X communication.
However, these technological uplifts surface several challenges, specifically in terms of security in the complex and heterogenous architectures expected to be used in V2X networks in 6G [13]. V2X communication is a critical technology that enables communication between vehicles, pedestrians, infrastructure, and other devices. Meanwhile, 6G communication is expected to enhance road safety and improve transportation efficiency. However, the implementation of V2X in 6G is also expected to lead to various unconventional risks and vulnerabilities [14]. The fundamental security challenge involved in V2X communication is ensuring the confidentiality, integrity, availability, authentication and access control (CIA3) in data transmission between vehicles and the infrastructure. Therefore, it is critical to ensure accurate and secure communication for safe operation of autonomous vehicles. Cybersecurity threats such as eavesdropping, altering, and Denial-of-Service (DoS) attacks can compromise the integrity of V2X communication, which could then lead to safety hazards on the road.
Various measures are actively being developed to address these security challenges, including the development of secure communication protocols, encryption techniques and intrusion detection systems. It is also important to establish a comprehensive security framework that incorporates all aspects of V2X communication, including hardware, software, and network infrastructure [15]. The advent of 6G has the potential to revolutionize a wide range of vehicular concepts, including CAVs, IoV, and V2V communication. However, this transformation will also come with significant security challenges, particularly in the context of the complex V2X communication architecture. Therefore, this paper aims to provide an in-depth analysis of the expected security challenges within V2X communication in the upcoming 6G era, while also proposing a novel security architecture to address these concerns. The core problem addressed in this paper is the security of V2X communication in the context of 6G networks [16]. As vehicles become increasingly connected and autonomous, they are also increasingly vulnerable to security breaches and cyber-attacks.
Figure 1 depicts the technological evolution of AI, vehicular technology, and security in vehicular communication. Vehicular technologies face unique challenges and constraints involving various factors such as safety, regulation, and consumer trust, which can slow down their advancement compared to other technology sectors. Although there is progress being made in these technologies, the cautious and complex nature of development within the automotive industry contributes to a perception that the industry is lagging behind where it should be to keep pace with advancements in technologies within other industries. Similarly, the automotive industry often involves longer product development cycles than other technology sectors. Developing, testing, and bringing a new vehicle to market can take several years; this extended timeline can slow down the integration of cutting-edge technologies in vehicles. Moreover, the rate of adoption for new vehicular technologies is often dependent on consumer acceptance and trust. In particular, consumers may be more cautious when it comes to entrusting their safety to advanced AI systems in vehicles, which can slow down the integration of such technologies.
The diverse and heterogeneous nature of V2X communication in 6G networks introduces unconventional security risks that can potentially jeopardize the CIA3 domains of vehicular systems [17]. It is therefore paramount to ensure the security of V2X communication to enable the safe and reliable operation of future vehicular networks [18]. This review addresses how the novel features of 6G networks, such as higher data rates, ultra-low latency, and massive device connectivity, impact the security landscape of V2X communication. This paper delves into the unique security requirements of V2X communication while focusing on aspects such as real-time communication, authentication of vehicles, and protection against cyber threats. This analysis also explores how V2X security can be enhanced by harnessing emerging technologies like Blockchain and Federated Learning (FL).
A. Related Previous Surveys / Reviews in the Literature
There has recently been a substantial increase in the number of research articles investigating V2X communication in 6G networks, with such studies covering a wide range of topics, including networking enhancements, applications, and security. With the continued advancement of technology, computer communication is moving toward 6G networks, and research in this area has reached unprecedented levels over the last three years. For the current review, we conducted a comprehensive search of SCOPUS and Web of Science databases to shortlist publications related to this topic; we found that only seven surveys from 2019 to 2023 focused specifically on security in V2X communication. One recent study [19] provided an overview of the V2X communication architecture with the aim of incorporating collaborative learning to augment cyber security.
Several works have presented similar surveys or reviews; however, these studies have to this point lacked a systematic security analysis with respect to V2X in 6G technologies. Moreover, such reviews have not covered the recent research spectrum in the V2X security domain related to FL and the concepts of blockchain in 6G-enabled V2X. Similarly, the existing literature works have not addressed the joint emerging security architecture of FL and blockchain in V2X-enabled 6G communication.
The authors in one prior study [20] provided a detailed discussion on enhancing V2X security using blockchain technologies and discussed the challenges involved in Beyond 5G communication. However, that study did not cover the security domain for threat analysis or countermeasures other than blockchain. Moreover, that study did cover the utilization of FL in V2X communication. Another study [21] focused on 6G-enabled vehicular network enhancement with Deep Learning (DL) techniques. That study comprehensively covered the architectural element in V2X communication, but it only contained a brief discussion on the security requirements and challenges. That study also did not cover FL implementation or the challenges involved in V2X communication.
Meanwhile, the authors in [22] provided a comprehensive review of 6G-empowered V2X communication while specifically focusing on reflecting surfaces. That study only partially covered the security of V2X communication concerning the physical layer. However, it did not provide a detailed security landscape describing relevant threats and countermeasures. Moreover, it did not address FL and blockchain emerging technologies. Another survey [23] provided a consolidated view of Machine Learning (ML)-based approaches for 6G-enabled secure vehicular networks. However, that survey did not provide a comprehensive view of the security issues in V2X communication, and it also did not cover blockchain technology in the V2X domain.
One prior study [24] conducted a security assessment of V2X integration with 6G networks. However, it did not systematically cover the complete security architecture, such as countermeasures, intrusion detection systems, etc. Moreover, that study did not cover blockchain and FL technologies. The authors in [25] provided a comprehensive discussion on 6G security and privacy issues. However, that survey did not provide an analysis of 6G security focusing specifically on V2X communication. Further, the authors of that study did not discuss V2X architecture alongside blockchain and FL. By contrast, our survey offers a critical analysis of the existing research that has scrutinized the security architecture, standards, challenges, and pertinent future research directions in 6G-enabled V2X communication. The unique contribution of our survey is its systematic security analysis through the CIA3 model and its analysis of countermeasures in all the architectural elements of 6G-enabled V2X communication.
B. Scope and Contributions
The literature review in the current paper is mainly focused on the keywords, “V2X security schemes”, “V2X authentication techniques”, “V2X access control system”, and “V2X confidentiality”, which we used to search for the latest relevant literature on various platforms, including Web of Science, Google Scholar, IEEE Xplore, SCOPUS, and ACM Digital Library. The goal was to identify proposed security schemes for 6G-enabled vehicular networks, and the shortlisted works were reviewed based on their reputation, relevance, originality, date of publication (between 2019 and 2023), and significance in the specific area. This review primarily includes papers in the area of 6G V2X communication that specifically discuss security mechanisms as their main subject. The search was initiated on 11/11/22 and continued until the submission for acceptance. The significant contributions of this survey are as follows:
This article presents a focused discussion on V2X communication architecture for emerging technological concepts in 6G. It also depicts the 6G-enabled V2X ecosystem in pictorial form for a broader overview. This article also provides an outline of the standardization approach in V2X and further analyzes the requirements of 3GPP release 18 to augment the next-generation networking concepts in 6G communication.
With the above premise, this study presents a comprehensive security analysis based on the CIA3 Model. This CIA Model3 is summarized in Table 3 through Table 7.
After conducting a detailed overview of the security paradigm of V2X in 6G networks, the present article deliberated upon the role of the emerging technologies of Blockchain and FL in the security architecture of V2X in 6G networks. This article also presents a generic security architecture based on Blockchain and FL for compatibility with dynamic V2X environments and 6G heterogeneous networks. In presenting this architecture, this review also deliberates upon the lessons learned.
After performing a comprehensive analysis of security in V2X, this study highlights a number of potential future research directions, including 1) V2X 6G Network Privacy in 3D Fog Computing, 2) V2X 6G Network Privacy in Augmented Reality, 3) Secure SDN architecture in V2X 6G networks, 4) V2X Physical Layer security in the THz spectrum, and 5) Blockchain-based distributed security in V2X.
C. Paper Structure and Organization
The rest of this paper is structured as follows. Section II discusses V2X architectural details that are important considerations in 6G networks. Section III presents an outline of standardization in V2X communication along with a discussion regarding security requirements. Section IV is the main focus of this review, which centers on a comprehensive CIA3-based security analysis of V2X communication. Section V highlights the role that the emerging technologies of blockchain and FL can play in security architectures for V2X in 6G networks. Section VI describes the proposed security architecture. Section VII deliberates on future research directions. This review article then concludes in Section 8. Figure 2 depicts the overall structure and organization of this review.
V2X Communication in 6G
A. V2X Communication
V2X communication encompasses all the communication technologies that enable V2V and V2I communication. These technologies can provide information to drivers and other vehicles in real-time while also improving safety and efficiency as well as reducing traffic congestion [26]. V2V communication allows vehicles to exchange information with other vehicles, including a vehicle’s speed, position, and direction of travel. V2V communication can help vehicles avoid collisions by coordinating their movements and optimizing traffic flow [27]. V2V communication can also be used to coordinate movements between vehicles, such as when vehicles are merging onto a highway or crossing an intersection [28].
Meanwhile, V2I communication allows vehicles to connect and exchange information with infrastructure, such as RSUs traffic lights or road signs. This type of communication can provide drivers with real-time information about road conditions, congestion, and potential hazards. V2I communication can also disseminate alerts among drivers in advance to warn them about an accident or roadwork ahead, thus allowing them to adjust their route or speed accordingly. Similarly, in cases of traffic jams or congestion, V2I communication can provide drivers with real-time information about the cause and duration of the delay, thus allowing them to alter their route as necessary and optimize travel time [29]. The anticipated growth in autonomous vehicles is sure to be associated with paired growth in the various communication and digital applications that are required to support them. As the number of connected and autonomous vehicles on the road continues increasing, there will be increased demand for services such as 3-D videos, holographic display systems, immersive entertainment, and improved in-car infotainment [30]. These developments will thrust the capacity bounds of current wireless networks and pose unconventional challenges to V2X networks in terms of bandwidth, delay, signals coverage, spectral utilization, energy consumption, cost competence, AI level, virtualization, and—most importantly—security [31].
Figure 3 illustrates the emerging network architecture for V2X communication, which encompasses several key planes. In the user interface plane, it highlights various communication types, such as V2V, V2Pedestrian, and Vehicle-to-Grid connections. Next, the data plane comprises intra-vehicle networks, pedestrian networks, EV grid networks, and vehicle-to-UAV networks. Lastly, the routing plane showcases technologies like edge computing, SDN, cloud computing, and intelligent network management. All of these elements are vital for enabling seamless V2X communication and facilitating the development of an intelligent transportation system that is prepared for the demands of 6G technologies.
B. V2X Standards
The establishment of C-V2X technology and advancements thereof involve multiple organizations, with the primary contributions coming from the 3rd Generation Partnership Project (3GPP), the European Telecommunications Standards Institute (ETSI), the Institute of Electrical and Electronics Engineers (IEEE), and the 5G Automotive Association (5GAA). IEEE is a well-known organization that is responsible for developing a wide range of technical standards, including those related to communication technologies. In the context of V2X communication, the IEEE 802.11 Working Group is particularly relevant; this working group has developed the IEEE 802.11p standard, which is designed for short-range communication in vehicular environments. IEEE 802.11p operates in the 5.9 GHz frequency band and is commonly used for V2X communication. ETSI is another organization that plays a major role in formulating V2X communication standards, particularly in the context of ITS. ETSI’s Technical Committee for ITS has developed standards for cooperative ITS communications, including ITS-G5, which is based on IEEE 802.11p technology. ITS-G5 standards are focus on enhancing road safety, traffic efficiency, and environmental sustainability through V2X communication [32].
The 3GPP is a collaborative organization that develops standards for cellular communication technologies, including 2G, 3G, 4G (LTE), and 5G. While 3GPP has not been directly involved in the development of V2X communication standards, it has considered the integration of V2X concepts into cellular networks to enhance communication between vehicles and other road users. The initial V2X standard established by 3GPP was based on LTE (Long Term Evolution) and 5G NR (New Radio) air interfaces. The initial work on LTE V2X was done under Release 14 (Rel. 14), and it was further improved in Release 15 (Rel. 15). The 3GPP then approved a Study Item (SI) under Rel. 15 to evaluate and compare proposals for LTE and NR V2X. The standardization and development of Rel. 16 NR V2X served as the precursor to this SI. The assessment procedure and conventions for LTE and NR V2X were developed under this SI. The 3GPP introduced a new SI along with a work item (WI) to formulate the initial set of 5G NR V2X standards in Rel. 16 [27]. Therefore, this approach by 3GPP produced the primary set of 5G NR V2X details. These details were made part of the 3GPP technical specifications (TS) [33].
The 5G NR standard was originally developed under Release 15; however, it did not include sidelink (SL) communication capabilities. Sidelink refers to direct communication between User Equipments (UEs) or terminal nodes without the data passing through the network. The requirements of such use cases could not be covered by the LTE V2X standard. Therefore, NR V2X SL was developed to complement LTE V2X SL communications. Overall, the introduction of NR V2X SL has expanded the capabilities of 5G technology to support new applications in the V2X domain. In the context of NR V2X, UEs can include vehicles, RSUs, or mobile devices carried by pedestrians. The 5G NR standard initially introduced V2X communications through Release 16 as the first version, including SL communications, based on the 5G NR air interface [34].
The 18th release and beyond refer to the next phases of development for the 3rd Generation Partnership Project (3GPP), which is an organization responsible for creating the technical standards for mobile telecommunications. These phases will focus on defining new use cases, SI, and WI with a focus on the 6th Generation (6G) of mobile networks by 2030. The development of 6G will involve significant advancements in wireless communication technologies to enable faster data speeds, reduced latency, and improved reliability compared to those of the existing 5G networks. The intricacies involved in V2X communication, which refers to communication between vehicles and other entities such as infrastructure, pedestrians, and other vehicles, will represent a crucial area of focus for 6G development [35].
The 3GPP will work on defining new use cases for 6G, which will include applications that require ultra-reliable, low-latency communication such as autonomous driving, telemedicine, and industrial automation. The SI will focus on research and analysis of various technical aspects of 6G networks, including new radio access technologies, spectrum usage, and network architecture. WI will involve the development of technical specifications and standards for 6G networks. This is expected to include the design of new hardware and software components, protocols for V2X communication, and the incorporation of unconventional technologies such as AI and ML into the network [36]. Systems that use high-frequency radio waves in the 20–100 GHz range are typically referred to as millimeter wave systems. These frequencies are currently being explored for their potential utility in 5G wireless communication systems, with future releases of 3GPP expected to utilize even higher frequency bands reaching up to 100 GHz. Terahertz wireless communication, which involves frequencies in the range from 100–300 GHz, is also an area of active research for potential use in 6G wireless [37]. One significant challenge involved in using THz level higher frequency bands for mobile communication is the typical requirement of directional transmissions. The energy of mm-Wave must be focused in a narrow beam to reach the intended receiver. Therefore, the need for precise alignment between the transmit and receive apertures makes it difficult to achieve beamforming in heterogeneously dense networks [38].
Moreover, one of the key objectives of 6G evolution is to increase the data rate of sidelink communication by adding the carrier aggregation (CA) feature. Carrier aggregation allows for the combination of multiple carriers to increase data throughput. Introducing CA in sidelink communication is expected to significantly improve the data rate, thereby enabling faster and more reliable communication between V2X devices [39]. Similarly, another objective is to extend sidelink operation to the unlicensed spectrum.
The unlicensed spectrum refers to the radio frequency spectrum that is not owned or licensed by any specific entity. It can enable V2X devices to communicate using frequencies that are not allocated to any particular organization, which can lead to increased efficiency along with reduced congestion in licensed bands [40]. The frequency range 2 (FR2) refers to the millimeter-wave spectrum, which provides high-frequency bands with wide bandwidths that are particularly suitable for high-speed communication. Enhancing sidelink support in FR2 can provide improved performance and reliability for V2X devices, especially in high-speed scenarios [41].
Moreover, the 3GPP is expected to develop a procedure to allow LTE V2X and NR V2X devices to co-exist in the same frequency channels. LTE and NR are two different cellular technologies that are used for wireless communication. Supporting both technologies in the same frequency channel can provide greater flexibility and interoperability for V2X devices, thus allowing them to communicate with each other regardless of the specific cellular technology they use [42]. 3GPP allows for the elective use of security implementation based on their ability to meet the required services. This means that the implementation of security measures is not mandatory in all cases [43]. However, 6G may require mandatory end-to-end encryption, which will pose a challenge in maintaining QoS in all services and applications. Moreover, it may be more costly to upgrade all current security protocols to support quantum-safe standards. Therefore, it may not be feasible to upgrade all existing security protocols to support quantum-safe standards in a short amount of time. Increased encryption operations through expanded key space are also likely to have a substantial effect on power consumption and storage requirements. This effect will lead to several concerns that are relevant for resource-constrained devices such as smartphones and IoT devices [44].
The 3GPP is responsible for developing standards for mobile communications technologies, and it should work more closely with researchers who use formal methods to investigate and verify the security of software and networks. Doing so could allow for potential security vulnerabilities to be identified and addressed before the standard is released. In this context, formal methods can be defined as mathematical techniques that are used to rigorously analyze and prove the correctness of software and systems. By using formal methods, researchers can identify potential security vulnerabilities and design more secure systems. This can help ensure that mobile communication technologies are more secure and less vulnerable to cyber-attacks [45]. Figure 4 shows a timeline of standards in V2X communication architecture.
C. V2X Transition From 5G to 6G Technologies
In the realm of telecommunications, the transition from 4G to 5G networks marked a significant leap in terms of speed, connectivity, and the ability to support a wide range of applications. However, as technology never ceases to advance, the next frontier in wireless communication is already on the horizon: 6G networks. Building upon the foundations established by their predecessors, 6G networks are poised to redefine the boundaries of connectivity and introduce novel concepts to address emerging challenges and opportunities. 6G is expected to continue the trend established in the evolution from 4G to 5G by providing even higher data rates and capacity, thus enabling unprecedented real-time data transfer and communication capabilities [46]. 5G significantly reduced latency, thereby enabling near-instantaneous communication and responsiveness. 6G aims to reduce latency even further, to the point of enabling applications that require URLLC for scenarios such as remote surgery, autonomous vehicles, and critical industrial processes. While 4G and 5G networks are primarily focused on utilizing the sub-6 GHz spectrum, 6G is expected to expand into higher frequency bands, such as the terahertz range. This will facilitate higher data rates and capacity, albeit with shorter propagation distances.
In the context of vehicular networks in particular, 6G technology presents both exciting opportunities and unique challenges compared to the established 5G vehicular scenarios. The key opportunities lie in ultra-low latency and ultra-high data rates, which can enable real-time, high-definition communication between vehicles and infrastructure, thus leading to safer and more efficient transportation. 6G’s improved positioning accuracy and sensing capabilities can also enhance autonomous driving and traffic management. However, there are also anticipated to be substantial challenges in this transition. Ensuring the reliability and security of vehicular communication is paramount, as even small disruptions can have life-threatening consequences. The massive scale of connected vehicles and the need for continuous, uninterrupted connectivity demand a highly robust infrastructure. There are also certain regulatory and standardization hurdles that must be addressed to achieve seamless global compatibility.
D. 6G Technologies
The 6G ecosystem includes revolutionizing the concepts of enhanced Mobile Broad-Band (eMBB), Secure Ultra-Reliable Low-Latency Communications (SURLLC), Un-Conventional Data Communications (UCDC), Big Communications (BigCom), and Three-Dimensional Communications (3DCom) [47]. Figure 5 shows an illustration of the ecosystem of 6G-enabled V2X communication.
eMBB refers to an advanced mobile network technology that offers higher data rates, improved spectral efficiency, and enhanced coverage to support data-intensive applications such as video streaming, virtual reality, and gaming. With the enhanced capabilities provided by eMBB, such as higher data rates, greater capacity, and improved coverage, 6G networks will ensure that even the most data-intensive applications remain seamlessly connected. Likewise, UCDC includes non-traditional communication methods that can transmit data over networks, such as wireless sensor communication, ad-hoc networks, and machine-to-machine communication. UCDC introduces unconventional methods of data transmission, such as using wireless signals for sensing and imaging, which opens doors to innovative applications in healthcare, agriculture, and security. SURLLC refers to a type of communication that ensures extremely high reliability, low latency, and secure communication links. SURLLC enables real-time communication for applications that require ultra-reliable low-latency connections, thus allowing for the control of remote surgeries, autonomous vehicles, and industrial automation. By contrast, 3DCom refers to a type of communication technology that enables the transmission of information in three dimensions. 3DCom enables communication in three-dimensional space, thus enhancing location-based services, augmented reality experiences, and the level of immersion involved in various interactions; this can include the use of technologies such as holographic displays. Moreover, BigCom includes the use of big data analytics techniques to analyze and optimize communication networks such as network optimization, traffic prediction, and anomaly detection. BigCom tackles the challenges posed by the exponential growth of data, thereby enabling the efficient processing and transmission of vast amounts of information. 6G networks promise a multitude of benefits that would transform industries and society as a whole [48]. As 6G networks continue to evolve, they hold the potential to revolutionize various industries and transform the way we connect, communicate, and interact with the world [49].
E. 6G Technologies in V2X
The current 5G NR-based V2X networks may not be able to meet the requirements of emerging intelligent communication and quantum computing technologies. Moreover, as traditional V2X communication networks can only provide partial integration with intelligent networks, a significant paradigm shift is required to keep pace with the extra versatile and diversified network approaches that are on the horizon, compared to traditional communication networks. This shift is expected to start with the emerging 6G wireless communication network attempt to unify terrestrial and non-terrestrial networks such as satellite and airborne communication networks [50].
6G is expected to bring together various technologies like millimeter-wave communications, terahertz frequencies, and integrated satellite systems. Integrating these technologies into V2X communication systems can also introduce complexities that make network deployment and management more challenging. As 6G technology is established and continues to advance, there will still be existing vehicles and infrastructure using older communication systems. Ensuring smooth interoperability between 6G-enabled V2X systems and legacy technologies is a crucial challenge that needs to be addressed [51]. Another relevant consideration is that the adoption of new technologies often comes with regulatory and standardization hurdles. The development of regulations and standards for 6G-enabled V2X communication systems must strive to balance innovation with safety and security considerations. Despite 6G’s focus on low latency, the stringent real-time requirements of V2X communication systems (especially for autonomous vehicles) may still pose challenges regarding their ability to consistently deliver the ultra-low latency needed for split-second decision-making [52].
A major potential benefit of 6G-enabled V2X is the development of an intelligent wireless communication system that aims to achieve the revolutionized concept of Intelligent Transportation Systems (ITS). The key features of 6G-enabled V2X include the integration of complex technologies such as Reconfigurable Intelligent Surfaces (RIS) enabled air interfaces, resource allocation, decision-making, cloud computing, Software Defined Networking (SDN), quantum computing, and various vehicular communication technologies. 6G aims to enhance the Quality of Service (QoS) of vehicular communication systems by using airborne networks and satellites in low Earth orbit to augment V2X systems with significantly enlarged and seamless coverage. This will help significantly improve the QoS parameters, specifically in certain low-coverage areas that are not covered by traditional terrestrial communication systems. Edge or fog computing and caching are lso game-changing technologies for the swift adoption of V2X communication in resource-constrained devices, as these can help achieve high-speed computation, highly accurate decisions, and longer battery life. The adoption of Visible Light Communication (VLC) in V2X networks will augment the traditional RF-based communications to help contribute to ultra-wide bandwidth, reduced setup cost, less power consumption, and improved security [53]. The use of VLC in 6G will enable user-driven connectivity through an intelligent and autonomous service platform for ITS by delivering an unprecedented travel experience to both passengers and drivers [54].
Moreover, 6G communications could potentially enable ultrahigh data rates exceeding those that we can currently imagine, such as reaching several gigabits per second, by utilizing mm-wave technology, VLC, and THz communications. Further, emerging state-of-the-art multicarrier frameworks, along with the latest resource allocation schemes, will support ultralow latency and reliable data transmission through multiple radio access technologies. For ubiquitous vehicular access and massive connectivity, two promising wireless paradigms are Non-Orthogonal Multiple Access (NOMA) [55] and satellite- or UAV-based V2X. Moreover, the integration of sensing and localization in communication networks is expected to contribute to more precise positioning and velocity estimation up to the cm-level and cm/s-level, respectively. Similarly, vehicle interfacing with intelligent infrastructures will be augmented with the ability to handle the complex physical and electromagnetic conditions in heterogenous networks [56].
Electric vehicles (EVs) are considered to potentially be major beneficiaries of 6G-enabled V2X. EVs have emerged as a recent focus of the automotive industry worldwide to counter the diminution of fossil fuels as well as the acceleration of global warming and environmental pollution. With 6G V2X, power optimization through the inclusion of various driving modes for EVs can significantly enhance both battery life and travel range [57]. Similarly, EV battery integration with cloud-based computation or machine learning (ML) can improve monitoring and allow for remote configuration of required changes [58]. Intelligent Reflecting Surfaces (IRS) can be used to improve V2X communication in coverage-limited scenarios, such as when operating at high-frequency bands like millimeter-wave or THz, or in unfavorable propagation conditions where communication links are obstructed. An example use case scenario is an out-of-coverage traffic intersection, where buildings and other obstructions can block V2V communication links, thus leading to degraded communication performance. In such a scenario, IRS can be used on the walls of buildings and at the intersection in the infrastructure [59]. The reflecting elements of the IRS can be fine-tuned to enhance the communication coverage of transmitting vehicles in perpendicular streets. By introducing enhanced multipath propagation, IRS can improve vehicular channel conditions and increase transmission coverage, ultimately resulting in better V2V communication performance. The signal-to-noise ratio in V2V links is sensitive to distance and quickly reduces away from the intersection due to blockages; the use of IRS can mitigate this issue [60]. The authors in [61] conducted a case study to evaluate the effectiveness of the IRS in improving vehicular communication in a scenario with a high traffic density of 60 vehicles/km. The results of that study showed that the utilization of IRSs can improve the signal of vehicles with line-of-sight (LOS) links by 25% compared to a scenario without IRS. Figure 6 shows the 6G network architecture integrated with V2X communication.
Proposed Architecture for FL enabled V2X communication with security dominance clusters.
V2X Communication Security
Ensuring the security of V2X communication is extremely critical for the safety and privacy of individuals as well as vehicles. Data transmitted between vehicles and infrastructure must be encrypted to prevent unauthorized access and data interception. Vehicles and infrastructure without a secure authentication process can leverage illegitimate entities to interfere recklessly. Therefore, access to the V2X network must be restricted to authorized entities only. Similarly, it is mandatory to maintain data integrity to ensure that data has not been modified during the transmission process [62]. V2X communication can reveal sensitive information, such as the location and behavior of vehicles. Therefore, various anonymity techniques are being explored to protect the privacy of individuals. Likewise, it is necessary for the firmware and software in vehicles and infrastructure to be securely updated regularly to address vulnerabilities and cyber threats. V2X communication architecture requires there to be redundant systems in place to ensure that no individual subsystem becomes a single point of failure for the whole system [63]. The encryption techniques used in 6G networks must be designed to provide stronger security and resist attacks from quantum computers, which are expected to become increasingly common in the future.
Similarly, applications involved in V2X communications depend on the transmission of information with other vehicles or roadside infrastructure to provision important services such as collision avoidance, traffic management, and improved navigation. However, this exchange of information also presents a potential security risk, as attackers can intercept, modify, or insert fake information in such communications. These vulnerabilities can lead to serious consequences such as accidents or traffic congestion [64]. Further, V2X communication involving the sharing of location information with other vehicles and traffic infrastructure. Any ill manipulation of location information is expected to cause devastating results. Moreover, the transmission of unencrypted location information can lead to serious privacy issues for users. Therefore, it is crucial to secure V2X communication to ensure the safe and reliable operation of V2X-based applications [65].
The CIA3 model is a framework that is extensively used to evaluate the security of systems. In the model name, CIA3 is an acronym for Confidentiality, Integrity, Availability, Authentication, and Access Control. The model provides a comprehensive approach for evaluating the security of a system, and it is used by security professionals to ensure that a system is secure against all possible threats [66]. Achieving security and protection of V2X communication necessarily involves dealing with sensitive information. Therefore, the CIA3 security model can be employed as an inclusive outline for evaluating the security of V2X communication in 6G networks. In the following sub-sections, we provide a detailed analysis of different attack scenarios and a CIA3 model-based security analysis of V2X communication in 6G.
A. Attack Scenarios in V2X
The V2X communication domains—such as V2V, V2I, V2P, and V2C—provide numerous benefits, such as improving road safety, traffic efficiency, and overall transportation experience. However, they also introduce security vulnerabilities that can be exploited by malicious actors. Some of the pertinent attack scenarios in V2X communication are as follows:
Denial of Service (DoS) Attacks: Attackers may transmit radio frequency interference to disrupt V2X communication, thereby causing jamming. This can lead to accidents and chaos on the road if vehicles and infrastructure are not able to communicate with each other effectively. Similarly, attackers can flood the V2X network with excessive messages, thus overwhelming the communication channels and causing legitimate messages to be lost or delayed, which is known as flooding [62].
Eavesdropping: Attackers may intercept V2X messages to gather sensitive information, such as location data or emergency signals. This information can be used for various malicious purposes, including tracking individuals or planning physical attacks [67].
Message Tampering: Malicious actors can alter or inject false messages into the V2X network. For example, they might send fake traffic signals or manipulate information related to a vehicle’s speed or direction. These actions could lead to accidents or traffic congestion [68].
Replay Attacks: Attackers capture legitimate V2X messages and replay them at a later time. For instance, an attacker can capture a legitimate emergency braking message and replay it to confuse or slow down nearby vehicles, which can potentially cause accidents [69].
Spoofing and Impersonation: In spoofing attacks, attackers mimic legitimate entities (e.g., other vehicles or infrastructure) to deceive V2X participants. They can send false messages that mislead vehicles or infrastructure elements into taking unsafe actions [70].
Sybil Attacks: An attacker creates multiple fake identities within the V2X network, potentially overwhelming it with bogus messages or undermining trust within the system [71].
Malware and Software Exploits: Infected vehicles or infrastructure components can spread malware or become victims of software exploits, which can compromise the safety and security of the entire V2X ecosystem [72].
Physical Attacks on Infrastructure: Physical attacks on V2X infrastructure, such as tampering with roadside units or traffic lights, can disrupt communication and cause traffic chaos or accidents [73].
Privacy Violations: Attackers may exploit V2X communication to track the movements and behavior of individuals, thus violating their privacy. This information can be used for stalking or other malicious purposes [74].
Data Manipulation: Attackers can manipulate V2X data to create fake traffic congestion or accidents, leading to inefficient routing decisions being made and potential gridlock [75].
B. Confidentiality in V2X
In next-generation V2X communication, the privacy and confidentiality of user data are of paramount importance. Primary public safety messages, such as traffic lights and speed limits, do not require data confidentiality. However, other V2X messages, such as private vehicle-to-vehicle messages, require data confidentiality to ensure user privacy, including user identity and positional information [76]. In 6G networks, V2X communication is expected to continue serving a critical role in enabling connected and autonomous vehicles to communicate with each other and with infrastructure elements. However, wireless communication in vehicular environments is also prone to various security threats to the confidentiality of transmitted messages. To prevent passive attacks, primary encryption and authentication mechanisms must be used in V2X communication.
However, ensuring confidentiality in V2X has become extremely complex due to the heterogeneous nature of the 6G network, which exists alongside the deployment of unconventional technologies such as AI, quantum computing, fog computing, etc. [77]. Anonymization is a technique used to protect the identity of users by removing any personally identifiable information (PII) from the data before transmitting it over the network [78]. However, the security and privacy requirements of V2X communication involve lawful identity resolution or de-anonymization, which refers to the ability to identify the real-world identity of a user or entity behind a pseudonym or anonymous identifier. This requirement is necessary for law enforcement purposes, such as investigating traffic violations or accidents. The authors in [79] have defined a broader set of technical details for lawful identity resolution in V2X communication. Pseudonymization is another technique wherein PII can be replaced with a pseudonym or unique identifier before transmitting the data over the network, thus allowing the data to be used for the analysis and optimization of the V2X communication system while still protecting the privacy of users [80]. Another study [81] proposed a framework based on blockchain and Name Data Network (NDN) technologies to provide verifiable secure V2X communication without using confidential user information. Instead, the framework uses non-confidential information, such as the number plate of the vehicle, for accountability of the communications. However, as personal credentials can still be extracted from the number plates of vehicles, there has been widespread research aiming to shift to intelligent number plates based on QR codes or barcodes for all CAVs to preserve user privacy [82].
Similarly, the authors in [83] proposed an authentication system that guarantees privacy and security through the joint usage of several techniques such as attribute signature, multi-receiver encryption (MRE), and message authentication code.
However, MRE requires more computation and communication resources than traditional encryption techniques, which can increase the processing time and network bandwidth requirements.
It is also possible to employ physical security measures to ensure data confidentiality in the network and protect against physical attacks on the network. One study [84] presented a phased-array physical layer security (PLS) scheme for millimeter-wave (mmWave) communications in cybertwin-driven V2X applications. The scheme in that work aims to reduce computational complexity by randomly swapping the pre-calculated initial weight vector elements, rather than directly calculating a new weight vector. However, randomly swapping the weight vector can result in degraded system performance, as the new weight vector may not be optimized for the specific system requirements. Similarly, the authors in [85] proposed an analytical framework for assessing the security performance of two association schemes in vehicular networks, including the smallest-distance association (SDA) scheme and the largest-power association (LPA) scheme. The SDA scheme associates the vehicle with the closest RSU, while the LPA scheme associates the vehicle with the RSU with the strongest received signal power. The analytical results show that the LPA scheme outperforms the SDA scheme in terms of confidentiality. However, the suggested beamforming scheme requires significant processing power, and it can be difficult to implement. Therefore, it is challenging to integrate into certain resource constraint systems or optimize it for specific applications. Table 3 provides a summarized view of the research works discussed above.
C. Integrity in V2X
In V2X communication, it is critical to guarantee data integrity to ensure that the information transmitted between vehicles and infrastructure is accurate, reliable, and consistent. Without data integrity, the safety and effectiveness of V2X communication systems can be compromised, which can in turn lead to potential accidents and system failures [86]. The authors in [87] proposed a technique for verifying the integrity of real-time sensor data as well asl detecting and localizing any tampering. That technique is based on semi-fragile data hiding, which involves inserting a binary watermark into the sensor data using a 3-dimensional quantization index modulation (QIM) technique. The decision-making unit can then use that watermark signature to detect and localize any tampering. The technique is specifically designed for LiDAR data, which is used in various applications such as autonomous driving.
The challenges of ensuring data integrity and reliability in V2X communication will continue to be important in 6G networks. Digital signatures used in 6G networks must also be designed to resist attacks from quantum computers, which can potentially break traditional cryptographic techniques used for signature verification [88]. The authors in [89] proposed a framework based on multi-layered edge-enabled V2X system models. To ensure the integrity of the data, that framework also includes a blockchain-based data integrity management scheme. This scheme ensures that the data remains secure and tamper-proof by storing it in a decentralized and immutable ledger. However, a multi-layered edge architecture with blockchain can be computationally expensive and require significant resources, which limit its scalability. A multi-layered edge architecture requires multiple technologies and protocols to be integrated and work together seamlessly. It can be difficult to achieve interoperability, and doing so requires significant collaborative efforts.
Similarly, another study [90] suggested a blockchain-based design that could be used to evaluate the integrity of the received data by considering the reputation score of the data sender. However, the accuracy of the reputation score depends on the quality and reliability of the data being used to calculate it. If the data is incomplete, inaccurate, or biased, then the reputation score may not be an accurate reflection of the data sender’s trustworthiness. The authors in [91] examined the use of blockchain technology to enhance the security and efficiency of a remote data integrity checking (RDIC) scheme for big data. By using an RSA digital signature and blockchain, a lightweight blockchain-based RDIC scheme was achieved. The RSA digital signature is susceptible to security vulnerabilities such as quantum computing-based brute-force attacks, side-channel attacks, and attacks on the underlying cryptographic algorithms. Similarly, blockchain technology face regulatory and computational energy challenges in some jurisdictions, which can limit its adoption and potential use cases.
In the context of data integrity in 6G networks, it is also crucial to standardize communication protocols and data formats. With the increasing diversity of devices and applications that may be involved in V2X communication, it is important to have standardized protocols and formats that can ensure interoperability and data integrity across different systems [92]. The authors in [93] described a protocol, named Outlier Detection, Prioritization, and Verification (ODPV), to address data integrity attacks in ITS applications using the isolation forest algorithm for the detection of outliers, fuzzy logic to prioritize the outliers, and C-V2X communications to validate the outliers. However, the performance of the isolation forest algorithm can degrade in high-dimensional data due to the increased computational complexity and sparsity of the data. Moreover, fuzzy logic can struggle with complex data relationships that may require the development of more sophisticated models to accurately capture the underlying patterns. One study [94] proposed the use of a Karatsuba-based ECC (Elliptic Curve Cryptography) processor as a security architecture to ensure a high level of data integrity and privacy in various forms of V2X communication. Karatsuba-based ECC requires more memory than traditional ECC techniques, as it involves precomputing some values and storing them in memory for later use. This can constitute a limitation for resource-constrained systems, such as embedded devices with limited memory.
The development of new communication standards, such as 6G NR-V2X, will play a crucial role in enabling V2X communication in 6G networks. It is also important for these standards to be designed to address the specific challenges and requirements of V2X communication, such as real-time data transmission, reliability, and security. Therefore, ensuring data integrity and reliability will continue to be a critical challenge in V2X communication in 6G networks, and the development of new techniques and standards will be needed to meet data integrity challenges [95]. Table 4 provides a summarized view of the above discussed research works.
D. Availability in V2X
Data availability is the ability of a communication system to ensure that data is accessible and usable when needed. In 6G networks, it will continue to be critical to ensure real-time data transmission and high network availability in V2X communication systems [96]. However, 6G networks are expected to introduce new capabilities and unconventional features that can help achieve the forecasted next-generation QoS through technologies such as IRS, intelligent beamforming, and NOMA [97]. These techniques can help ensure that data is transmitted reliably and with low latency, even in the presence of interference. One study [98] suggested that, in order to ensure that the system can provide a consistent level of performance across different channel qualities, the count of reflecting elements used to serve users near or far can be derived based on the specific channel conditions in IRS-enabled V2X communication. That study showed that the system can improve availability through optimized power allocation to maximize the sum-rate of data transmission to all users. However, the performance of IRS is heavily dependent on the availability and accuracy of channel state information (CSI). Any errors or uncertainties in CSI can affect the performance of IRS, particularly in dynamic V2X environments where the channel conditions are constantly changing. Likewise, the authors in [99] proposed an optimization framework that could be used to reduce the total transmit power of Backscatter (BC)-NOMA cooperative V2X networks while ensuring a high quality of service. This framework involves jointly optimizing the transmit power of both the base station and the roadside units, along with the reflection coefficient, to minimize the overall transmit power. Optimization is performed using an iterative sub-gradient method by iteratively updating the optimization variables until achieving minimum transmission power under conditions of both perfect and imperfect channel state information.
Similarly, among several key features of 6G communication will be its ability to support ultra-low latency and high-bandwidth communication in real-time data transmission in V2X communication systems. Therefore, V2X in 6G networks must be designed to leverage low-latency and handle high-bandwidth connectivity to support time-critical applications such as emergency services and collision avoidance [100]. 6G networks will also be designed to provision services to massive numbers of connected devices, which presents scalability challenges for ensuring high network availability in V2X communication. Therefore, integrated and heterogeneous scenarios of a large number of devices and users in 6G will require maintaining high availability to minimize the impact of downtime on V2X communication systems [101]. The authors in [102] proposed a framework called FL and edge Cache-assisted Cybertwin (FLCC) to provide individual user-specific services in 6G-V2X. The FLCC framework utilizes both edge cooperation and optimizations by employing a Federated Multi-agent Deep Reinforcement Learning-based (FM-DRL) algorithm. That framework augments the network availability using a caching mechanism based on the Federated Reinforcement Learning-based Edge Caching (FREC) algorithm to acquire the required training datasets with minimum bandwidth and computational load on resource-constrained systems in vehicles. FL involves training models on distributed data, which leads to concerns regarding data privacy and security. However, the proposed FLCC framework requires the incorporation of appropriate privacy-preserving measures such as Differential Privacy (DP), Secure Multi-Party Computation (SMPC), and Homomorphic Encryption (HE) to protect user privacy from inference attacks.
In 6G networks, it will be even more crucial to ensure data availability in V2X communication due to the growing demand for high-speed, reliable communication services. Therefore, to support time-critical applications, V2X communication systems must be designed with redundancy and fault tolerance mechanisms to handle the event of hardware or software failures and minimize downtime among critical services [103]. One study [104] suggested a Byzantine-Fault-Tolerant Consensus via Reinforcement Learning (RL) for permissioned Blockchain implementation to optimize mobility during blockchain transactions in V2X communication. The proposed scheme can have vehicles perform optimum channel selection and switching as a fault-tolerant measure for maximum availability in the network. Byzantine fault tolerance algorithms typically require large amounts of computational resources to achieve consensus. This can be a limiting factor for systems with limited resources or high-performance requirements. Byzantine fault tolerance also assumes that nodes in the system can detect and isolate malicious behavior. This can make it difficult to detect and respond to malicious behavior, particularly when that behavior is sophisticated or disguised.
Similarly, to ensure network availability, V2X communication systems in 6G networks should consider using continuous real-time monitoring techniques to identify issues [105]. Moreover, load balancing techniques are potential solutions that can help distribute traffic across multiple nodes to ensure that no single node becomes overwhelmed, thereby helping ensure that data services remain available even under heavy load. V2X communication systems must be designed with intelligent load-balancing schemes so that they can handle the increasing volumes of data that will be coming from multiple devices and support a growing number of users without compromising data availability [106]. QoS mechanisms are also essential for ensuring data availability in V2X communication to prioritize time-critical applications, such as emergency services and collision avoidance. To withstand interference from other wireless networks and environmental factors, V2X communication systems in 6G networks must be designed to be resilient to interference. To achieve this, the authors in [107] proposed an algorithm for scheduling multiple users in 6G ultra-massive MIMO systems in V2X communication using block diagonalization (BD) precoding techniques, which are sensitive to the correlations between channels. The algorithm uses a mathematical technique called the Pearson coefficient to calculate the channel matrix into a vector form to measure the channel quality based on the noise enhancement factor. The algorithm jointly considers the correlation between the channels of different users and their channel quality to select the users with the highest quality channels while minimizing the correlation between channels. This approach ensures the selection of high-quality channels while reducing interference between channels due to correlation. However, the Pearson coefficient measures the linear association between variables but does not capture the strength or direction of the relationship. This can limit its usefulness in complex heterogenous networks in which the strength or direction of the correlation is important. Moreover, the coding scheme BD requires a significant amount of computation, particularly for large MIMO systems. This can be a limiting factor for real-time applications or systems having limited computational resources, such as IoVs.
Moreover, the associated technologies in 6G communication, such as cloud computing, SDN, network virtualization, AI, and fog computing, can provision backup and recovery procedures in V2X to quickly restore data services in the event of a failure and minimize downtime [108]. Table 5 provides a summarized view of the above discussed research works.
E. Authentication in V2X
Data authentication involves verifying the identity of the sender and confirming that the data is not tampered with in the process of transmission. V2X communication requires fast and reliable authentication mechanisms to support time-critical applications such as emergency services and collision avoidance. Authentication mechanisms must be designed to work quickly and efficiently to minimize delays and ensure that data is transmitted in real-time [109]. The authors in [110] proposed a multicast service model for vehicles to securely connect them to a content provider using distributed keys in an RAN-enabled mobile network. The proposed scheme ensures the authentication and protection of multicast service data and key distribution while maintaining anonymity and protocol attack resistance. However, as the number of group members increases, the complexity involved in managing group keys and member authentication also increases, which eventually leads to scalability issues. Moreover, the compatibility of the multicast authentication scheme with different network architectures and technologies can also pose a challenge, particularly in heterogeneous network environments.
In the context of 6G networks, the challenges involved in and requirements of data authentication in V2X communication are complex when compared to those in previous generations of wireless networks. 6G networks are expected to introduce new capabilities and features that can impact the design and implementation of authentication mechanisms such as AI, quantum computing, fog computing, etc. [111]. One study [112] proposed a blockchain-based scheme for cellular vehicle-to-everything (C-V2X) ecosystems in 6G networks. That proposed scheme utilizes network function virtualization (NFV) to optimize edge-resource allocation. Further, data aggregation through the 6G sensors is securely performed at the data plane, and the aggregated data is transmitted to the NFV control plane. The aggregated data is then used to allocate resources to connected autonomous smart vehicles (CASVs) through edge nodes.
The proposed scheme provides an efficient and secure method for data aggregation and resource allocation, which is essential for the reliable operation of CASVs in C-V2X ecosystems. However, it can be difficult to allocate resources to different NVFs efficiently and effectively, particularly in large-scale networks. It can also be difficult to ensure compatibility between different VNFs from different vendors, especially in heterogeneous network environments.
One of the key features of 6G networks is their ability to support ultra-low latency and high-bandwidth communication, which is essential for time-critical applications such as V2X communication. Therefore, authentication mechanisms must be designed to incur minimum delay to ensure that data is transmitted in real-time [113]. The authors in [114] proposed a secure authentication scheme for vehicle-to-everything (V2X) communication, which aims to provide a high degree of security in various different types of vehicular communication (V2V, V2I, V2N). That proposed approach uses lightweight cryptographic algorithms to safely receive all keys and messages from RSUs, vehicles, and the network. That scheme provides an efficient and secure method for authenticating V2X communication while ensuring lower computation and operational costs. However, although such lightweight cryptographic algorithms are designed to be computationally efficient, they may not provide the same level of security in emerging quantum computing paradigms in 6G networks.
6G networks are also expected to introduce new security threats, such as quantum-based attacks, that may require the development of new authentication mechanisms [115]. Privacy concerns are also expected to be a key consideration in 6G networks, given the sensitive nature of the data that is exchanged during authentication in V2X communication. Therefore, authentication mechanisms must be designed to protect user privacy and prevent unauthorized access to sensitive data [116].
The authors in [117] proposed a group-based handover authentication strategy for 6G heterogeneous networks to improve efficiency and security. That system includes the user equipment (UE), access points such as gNB and eNB, authentication servers, and blockchain. To access network services, the UE must first perform initial authentication and key negotiation with the local server. The proposed scheme then performs handover authentication and batch authentication for individual or group users, depending on the number of users. The scheme uses blockchain and aggregated signature technologies to achieve global switching authentication and D–H key exchange to enhance security and decrease the one-by-one authentication time. However, it can be difficult to implement and manage aggregated signatures, particularly in terms of key management and secure communication. Similarly, aggregated signatures can introduce performance overhead due to the additional computation and communication required for signature aggregation, which can in turn affect the overall performance of the system.
Moreover, the limited computational resources of vehicles and devices participating in V2X communication may pose challenges to the design and implementation of authentication mechanisms in 6G networks [118]. Therefore, only resource-efficient authentication mechanisms are expected to effectively minimize the impact on device performance. Similarly, secure key management mechanisms are the most complex part of authentication in V2X communication systems for ensuring that only authorized entities can access and use encryption keys [119]. Likewise, digital signatures are suitable to authenticate data and ensure tampered-free transmission in V2X communication [120]. V2X communication systems are generally expected to be compatible with digital certificates to ensure compatibility with legacy security architecture. Digital certificates provide a way to verify the identity of the sender and ensure that the data is transmitted securely through trust in a Certification Authority (CA). V2X communication systems can use certificates for secure communication protocols such as TLS (Transport Layer Security) [121]. Table 6 provides a summary of the above discussed research works.
F. Access Control in V2X
Access control refers to the process of controlling the actions a user can take after they have been authenticated in a network or system. Access control systems typically use a set of allowed or prohibited rules or policies to restrict the actions of a given user or group of users. The purpose of access control is to limit the scope of an authenticated user in a system or resource. Access control in V2X communication in 6G networks faces several challenges due to the unique characteristics of the communication environment [122]. V2X communication in 6G networks may involve a wide range of devices having different communication capabilities and security requirements. It is crucial that any access control mechanisms used in V2X communication work seamlessly across these heterogeneous devices, and that only authorized entities can access sensitive data [123]. The authors in [124] proposed a blockchain-based access control ecosystem that could be used to manage large data sets and protect against data breaches. That ecosystem gives asset owners sovereign control over access control, and it uses the Linux Foundation’s Hyperledger Fabric blockchain to implement smart contracts or transaction processing functions. By using a blockchain-based access control ecosystem, the proposed system offers enhanced security, transparency, and immutability compared to traditional access control systems. However, although Hyperledger Fabric supports private channels and transactions, the level of privacy is not as strong as that provided by some other blockchain platforms. Moreover, Hyperledger Fabric may not scale well for extremely high transaction volumes in dense and massive 6G V2X connectivity.
Massive connectivity is the hallmark of 6G communication, which presents scalability challenges for access control mechanisms. Access control mechanisms in V2X communication must be designed to be able to easily scale up so that they can support large numbers of devices and users while maintaining efficient and reliable operation [125].
The authors in [126] proposed a protocol called the Network Coding-based Medium Access Control protocol (NC-MAC) for supporting V2V beacon broadcasting using distributed network coding. The protocol combines feedback mechanisms, such as the process of retransmission and coding in the network to improve broadcasting reliability. The NC-MAC protocol improves communication reliability and scalability in various situations, including roads with clusters of urban vehicles. However, the use of network coding introduces additional overhead due to the need for encoding and decoding packets, which can increase latency and reduce throughput. Network coding also introduces new security challenges, such as the potential for attacks on the coding coefficients used for packet encoding and decoding.
Likewise, V2X communication in 6G networks must support real-time applications such as autonomous driving and traffic management. Access control mechanisms must operate quickly and efficiently to minimize delays and ensure that they can support real-time applications [127]. Moreover, 6G communication may face several unconventional security threats, including hacking, data breaches, and denial-of-service attacks. Therefore, the critical safety requirements of V2X communication necessitate the implementation of robust access control mechanisms to detect and prevent these threats [128]. The authors in [129] proposed a multi-dimensional Discrete-Time Markov Chain (DTMC)-based model for analyzing the efficiency of IEEE 802.11p and C-V2X Mode 4 protocols at MAC layer. The models consider periodic cooperative awareness messages (CAMs) and event-driven (decentralized environmental notification messages) DENMs to obtain closed-form solutions for the steady-state probabilities. The solution includes expressions for key performance metrics for the performance enhancements for both standards IEEE 802.11p and C-V2X Mode 4 in terms of delay, collision probability, and channel utilization. However, DTMC models assume that the system has no memory, meaning that the future state of the system depends only on the current state and not on the past. This assumption may not hold in all cases, which can limit the accuracy of the model predictions. Moreover, multi-dimensional DTMC models are highly complex and require significant computational resources for analysis, which can be a challenge for resource-constraint IoVs.
Similarly, V2X communication involves the exchange of sensitive data, which inherently raises privacy concerns. Therefore, access control mechanisms must be designed to protect user privacy and prevent unauthorized access to such sensitive data [131]. The authors in [130] proposed a solution for the incorporation of an authentication mechanism for addressing the security issues in VANETs. That approach uses identity-based encryption for access control and deep learning-based techniques to filter malicious packets. The identity-based encryption technique INDistinguishability under selective-ID Chosen-Ciphertext Attacks (IND-sID-CCA) secure, when used along with the deep learning algorithm, provides accuracy of 99.72% to detect malicious packets. However, IND-sID-CCA secure IBE systems can be computationally intensive, particularly for large-scale deployments with many users. This can impact the system’s performance and scalability. Moreover, IND-sID-CCA secure IBE systems may not be compatible with other security mechanisms or protocols, which can limit their interoperability with other systems. V2X communication in 6G networks must comply with various regulations such as data protection laws, which may present additional challenges for access control mechanisms. Access control mechanisms must be designed to comply with these regulations while ensuring that data is transmitted securely [132]. Table 7 provides a summarized view of the research works discussed above.
V2X Security in Emerging Technologies
As we approach the 6G era, there are several emerging technologies that are poised to transform the way devices communicate and interact with each other. The most prominent of these technologies, blockchain and FL, are the most impactful. The subsequent subsection will elaborate upon the impact of these technologies on 6G-enabled V2X communication.
A. Blockchain in 6G-Enabled V2X
Blockchain is a distributed ledger technology that enables secure and transparent transactions without the need for intermediaries. It is often associated with cryptocurrencies like Bitcoin, but its potential extends beyond finance. For example, in a 6G context, blockchain could be used to securely and efficiently manage the vast amounts of data that are generated by the network devices that are anticipated to become ubiquitous in the 6G era. One of the key benefits of blockchain is its ability to establish trust in a decentralized network. Each block in the chain contains a cryptographic hash of the previous block, thus making it impossible to modify or tamper with the data stored in the chain. This immutability makes blockchain an ideal platform for securing sensitive data and ensuring that it is not tampered with [133]. The authors in [134] proposed a blockchain-based solution that involves developing a formal mathematical model for a system that considers the interconnectedness of objects and V2X information channels. Their proposed solution also includes an algorithm that is designed to efficiently offload traffic to a mobile edge computing (MEC) server. The focus of the work is on energy efficiency, which is an important consideration in V2X communication. This solution aims to improve the efficiency and effectiveness of V2X communication in terms of data transfer and processing. Their proposed solution has the potential to contribute to the continued advancement of V2X technology, and it could have practical applications in areas such as smart transportation systems.
Blockchain is an emerging technology that could play a significant role in enabling secure and efficient V2X communication. One of the primary challenges involved in V2X communication is ensuring the security and privacy of the data transmitted between vehicles and infrastructure elements. Blockchain is a distributed ledger technology that offers a secure and transparent way to manage data. Blockchain can be used to make V2X communication more secure, transparent, and tamper-proof. In a blockchain-based V2X system, each vehicle and infrastructure node would have a unique digital identity that would be recorded on the blockchain. The blockchain would then be used to manage the communication between nodes, thereby ensuring that data is only shared with authorized parties [20].
Another benefit of blockchain-based V2X communication is that it enables the creation of decentralized applications that can run on a blockchain network, thus enabling secure and transparent transactions without the need for intermediaries. In the context of V2X communication, decentralized applications could facilitate secure and efficient micropayments between vehicles and infrastructure, such as tolls or parking fees. Blockchain could also enable the creation of new business models and revenue streams in the V2X ecosystem.
As one example, a blockchain-based V2X system could allow vehicle owners to monetize their data by sharing it with authorized third parties in exchange for compensation [135]. The authors in [136] proposed a method for integrating blockchain technology into vehicular networks to improve cybersecurity. That proposed method uses a decentralized, collaborative system to dynamically create communities that can revoke malicious vehicles in real-time, which helps address challenges such as Sybil and faking position attacks. The article presents analytical models of the system of real-time revoking of certificates while also examining the solution’s impact on these types of attacks. The proposed method was tested using real V2X hardware, and the experiments demonstrated the feasibility and benefits of real-time revocation via vehicle communities.
However, there are several remaining challenges that need to be addressed before blockchain can be effectively implemented in V2X communication, including issues related to scalability, privacy, interoperability, standardization, and the integration of blockchain with existing V2X systems. Overcoming these challenges will require collaboration between industry stakeholders, along with further research and development in the field of blockchain technology for V2X communication.
B. Federated Learning in 6G-Enabled V2X
6G networks are considered to be intelligent networks, because they are expected to be designed using advanced technologies such as artificial intelligence (AI), machine learning, and edge computing. These technologies enable the network to adapt to changing user needs while dynamically allocating network resources as needed to support various applications and services. Intelligent networks are designed to be more flexible, resilient, and efficient than traditional networks. They can automatically adjust to changing traffic patterns and optimize the use of network resources, ultimately providing faster and more reliable connectivity to users. Intelligent networks can also provide new services and applications that could not be possible using earlier generations of wireless networks [137].
FL is a machine learning technique that allows multiple devices to collaboratively learn from a shared model while keeping their data private [164]. In the context of V2X communication, FL could be used to train machine learning models on the massive amounts of data generated by vehicles and infrastructure, thereby leading to more accurate predictions and better decision-making [138]. The authors in [139] proposed a new approach called consensus-driven FL (C-FL) for PointNet-compliant deep ML architectures and Lidar point cloud processing for road actor classification. The approach is modular and decentralized, and it is evaluated by simulating a V2X network based on the Collective Perception Service (CPS) for mutual sharing of the PointNet model parameters. The performance evaluation considers the impact of the vehicular network’s degree of connectivity, the benefits of continual learning, the convergence time, and the loss/accuracy tradeoffs with heterogeneous training data. The proposed method has the potential to improve the accuracy and efficiency of road actor classification in V2X networks by leveraging a decentralized approach to FL.
One of the primary challenges involved in V2X communication is ensuring the privacy of the data transmitted between vehicles and infrastructure. Federated learning allows for machine learning models to be trained without requiring data to be shared, thus ensuring data privacy. Instead, the machine learning models are sent to the devices themselves, which then contribute their learnings back to the central model. This approach ensures that sensitive data is not exposed while still allowing for the creation of accurate machine learning models [140].
FL also enables distributed machine learning, thus allowing for the more efficient usage of computational resources. Instead of relying on a central server to train machine learning models, FL distributes the workload across multiple devices, which results in faster and more efficient training. This distributed approach is particularly useful in the context of V2X communication, where the amount of data generated is both massive and constantly growing [141]. The authors in [142] proposed a novel privacy-preserving computing model called AFLPC, which is designed for asynchronous FL in 5G-V2X scenarios. That model utilizes an adaptive differential privacy mechanism to protect data privacy while also minimizing noise. In the present work, we also proposed a weight-based asynchronous FL aggregation update method that controls the proportion of parameters submitted by users with different training speeds and updates the aggregation parameters of lagging users to reduce the negative impact on the model caused by varying speeds. The experimental results demonstrate that the proposed approach effectively ensures the credibility and privacy of asynchronous FL in 5G-V2X scenarios while simultaneously improving the model’s utility.
Similarly, FL could be used in the creation of predictive maintenance models for vehicles. By using machine learning models trained on data from multiple vehicles, it could be possible to develop predictive maintenance models that identify and predict issues before they occur. This approach could help reduce maintenance costs, improve vehicle safety, and prolong the service lives of vehicles [143]. However, FL in V2X communication faces several challenges, including the heterogeneity of data as well as the varying computational capabilities of different vehicles and roadside units. It is also extremely difficult to ensure data privacy while facilitating effective collaboration among the participants. Communication problems such as high latency and intermittent connectivity can also impact the learning process. Likewise, maintaining the consistency and accuracy of the learned model across all participants while managing the efficient aggregation of model updates from different sources constitutes another challenge. It is also crucial to avoid overfitting and data imbalance to ensure that the learned model generalizes well to new data.
C. Blockchain-Enabled FL Based Security in 6G-Enabled V2X
The incorporation of blockchain technology and FL can significantly enhance their roles within 6G scenarios when compared to their utilization in 5G contexts. In 6G, blockchain can play a crucial role in securing and managing the vast amount of data that is generated by an even more extensive network of connected devices. Its decentralized, immutable ledger can provide a trust layer for transactions and data exchange, thus ensuring data integrity and privacy, which is particularly vital in the context of critical applications like autonomous vehicles and remote healthcare. By contrast, FL is expected to become more relevant in 6G due to its ability to train machine learning models across a multitude of edge devices while preserving data privacy. This is expected to become essential as 6G supports an increasingly massive number of IoT and edge devices, thus making it inefficient and potentially insecure to centralize data for training. Federated learning allows devices to collaboratively train models while keeping data on the device, which mitigates privacy concerns.
Blockchain-enabled FL is a potential approach that might be useful for improving the security architecture of 6G-enabled V2X communication networks. The FL framework uses a distributed learning approach whereby multiple devices collaborate to train a shared model without sharing any sensitive data. The blockchain component is used to ensure the integrity of the learning process while also managing access to the shared model. This architecture can enhance the privacy and security of V2X networks by ensuring that sensitive data remains secure while still allowing for the efficient sharing of knowledge. By implementing blockchain-enabled FL, V2X networks can achieve a higher level of security, which is crucial for the safe and reliable operation of autonomous vehicles and other connected devices [144].
Intelligent connected vehicles (ICVs) generate vast amounts of data within the V2X environment, and this data can be harnessed securely and efficiently through decentralized techniques such as FL. However, traditional FL systems are susceptible to attacks, and they fail to meet the security requirements for practical use. If a compromised or malicious ICV uploads incorrect or low-quality local model updates to the central aggregator, it could lead to a decrease in the accuracy of the global model, which would reduce drivers’ safety and efficiency. It is therefore critical to ensure the security of FL in V2X environments to protect the privacy of drivers and enhance the reliability and safety of the overall system.
The increasing use of software and wireless interfaces in the vehicular networks built by interconnected vehicles and transportation infrastructure has made them more susceptible to cyber-attacks. To mitigate this risk, intrusion detection systems (IDSs) can be customized to efficiently detect such attacks. Machine learning approaches have made significant progress in detecting malicious attack traffic in vehicular networks [165]. One prior study [145] proposed a cooperative intrusion detection mechanism that involves distributing the training model to edge devices such as connected vehicles and RSUs. This usage of a federated-based approach reduces the resource utilization of the central server while maintaining security and privacy. The proposed mechanism also utilizes blockchain for the storage and sharing of the training models to ensure the security of the aggregation model. Through this approach, the training process becomes more efficient and secure, which makes it suitable for use in distributed environments with limited computing resources.
It should be noted that none of the existing blockchain-enabled FL solutions have fully addressed and examined the security architecture requirements in the CIA3 domain. This means that current solutions may not provide a robust and comprehensive security mechanism to protect the integrity and privacy of the data during the FL process. There is therefore a need for an integrated security architecture that covers all aspects of the CIA3 domain to ensure a secure and reliable FL system that can be applied to various use cases, including in ICVs. Therefore, the next section presents the Blockchain-enabled FL based generic security architecture proposed in this study for V2X communication.
D. Proposed Generic Security Architecture
Blockchain and FL technologies are emerging as joint manifestations of secure intelligent networks in 6G communication. FL can improve the privacy of blockchain networks by allowing multiple entities to collaborate on training machine learning models while keeping their data decentralized and secure. This means that sensitive data remains on local nodes and is not shared across the entire blockchain network, which reduces the exposure of data to potential security breaches. This proposed architecture considers the security requirements of CIA3 domains as a highly dynamic phenomenon due to heterogeneous network and vehicular domains including IoV, V2V communication, infrastructure, Vehicle to UAV links, etc. Security measures that are as strong and foolproof as possible result in various compromises to legitimate uses as well as increased complexity, network overload, and computational costs. Therefore, the proposed architecture suggests the foundational implementation of blockchain through CIA3; however, the dynamic requirements are to be controlled, monitored, and adjusted using FL techniques for minimal compromise to legitimate users and network services. The proposed architecture suggests real-time modification in security settings and security protocol through FL. The proposed architecture stands to provide a broader prospect in the context of 6G communication networks. It suggests the use of a unique approach to addressing security concerns by combining blockchain and FL technologies. While both blockchain and FL have been used in various domains, their joint application in the context of secure intelligent networks for 6G communication is relatively new and represents a novel approach to enhancing security and privacy.
E. Design of Proposed Architecture
The proposed architecture suggests a hierarchical implementation of FL, starting from IoV (e.g., connected vehicles) and extending to core networks (e.g., cloud servers). The goal of FL models in this architecture is to learn from available data and real-time scenarios to generate an efficient hierarchy. This includes the selection of optimal RSUs, vehicles, and other infrastructure as part of the FL process. These local models are then hierarchically aggregated and updated in a cluster-level global model, and they are ultimately input into an overall global model. The proposed architecture also considers the selection of optimum miners for the Blockchain, which is a decentralized ledger technology that can be used for secure data sharing and verification in FL. The security settings for the FL process, such as confidentiality, integrity, authentication, and access control, are adjusted based on the specific requirements of the different services and applications that may exist in the IoV ecosystem. Moreover, the security domain in CIA3 does not need to be simultaneously covered for all aspects of FL in the proposed architecture. For example, in the case of safety and hazard-related information broadcast, confidentiality may not be a primary requirement, but integrity and authentication are necessary. The access control requirements are also continuously changing based on the type of vehicles and corresponding services, such as law enforcement, health services, disaster management, schools, etc.
The primary use of blockchain technology is authentication and integrity based on the technology’s immutability and distributed ledger. This means that blockchain is commonly used to ensure that data is secure, unalterable, and stored across a network of computers, thus making it tamper-proof. However, conventional schemes can be used to increase the availability, confidentiality, and access control of blockchain. This implies that traditional security measures can be used in conjunction with blockchain to enhance its functionality and security. The relationship between these conventional security schemes and blockchain, as well as any necessary adjustments, will be governed through FL. The implementation of blockchain in a holistic manner can result in challenges related to resource utilization. This means that the effective utilization of resources such as computing power, storage, and network bandwidth may be difficult in a comprehensive blockchain implementation.
Similarly, the major aim of FL in the context of blockchain implementation is to optimize the adjustment of the blockchain based on several features that have been extracted from V2X communication systems. V2X communication systems allow vehicles to communicate with each other—as well as with infrastructure elements and other entities—for various purposes such as improving road safety and traffic efficiency. Some of the features that can be used to optimize blockchain implementation include considerations of the number of vehicles, vehicle concentration, perceived threat, available resources, interference, vehicle speeds, and load balancing. These features can provide valuable insights and data points for adjusting the blockchain implementation to better meet the specific needs and requirements of the V2X communication systems. The number of vehicles and vehicle concentration can indicate the scale of the V2X communication system, and adjusting the blockchain accordingly can help ensure efficient data processing and storage. Perceived threat refers to the potential risks and vulnerabilities in the V2X communication system, and the blockchain implementation can be optimized to include enhanced security measures to mitigate these threats. Similarly, available resources, interference, and vehicle speeds can impact the performance and efficiency of the V2X communication system, while optimizing the blockchain can help ensure optimal resource allocation and data transmission.
However, the integration of blockchain technology and FL holds significant promise in addressing compatibility challenges within the dynamic V2X environment and the complex 6G heterogeneous networks. The data integrity and security of V2X communications can be ensured by making use of the decentralized and tamper-resistant nature of blockchain, thus fostering trust among vehicles, infrastructure, and users [146]. FL complements this by enabling collaborative model training across various network nodes without centralized data sharing, which preserves individual privacy and reducing communication overhead. This combination allows for real-time updates and model refinements to adapt to the rapidly changing conditions of V2X and 6G networks, thereby enhancing overall system efficiency and responsiveness [147].
FL is expected to enable adjustments in the blockchain implementation based on the features that have been extracted from the local data of the collaborating entities. This means that each entity will adjust the blockchain implementation based on its specific needs, requirements, and local conditions, ultimately leading to a more customized and optimized blockchain network. Moreover, FL will facilitate interoperability between different blockchain networks by allowing entities to collaborate on machine learning models without having to share their data with each other. This can enable cross-chain collaborations and data sharing, in turn leading to enhanced interoperability between different blockchain networks. Similarly, blockchain’s decentralized and tamper-resistant nature could enhance data integrity and authentication within VLC networks, thus safeguarding any sensitive information exchanged between vehicles and infrastructure. Moreover, the privacy-preserving capabilities of FL might enable collaborative model training while preserving individual data privacy. However, various challenges, such as the high computational demands of blockchain and FL, as well as the latency-sensitive nature of V2V and V2I communication, should be carefully addressed for practical implementation. Thus, while the concept holds promise, it must be investigated in a thorough analysis of its performance, efficiency, and real-time constraints before this security architecture can be adopted in VLC systems [139]. Moreover, a systematic approach needs to be used to implement a smart transportation system with unique digital identities using VLC and blockchain. Each vehicle and infrastructure node would be equipped with a unique digital identity, possibly through RFID tags or QR codes, which would be associated with their VLC transmitters. These digital identities ensure that each entity is distinguishable and can be tracked. VLC technology utilizes light signals for communication. Each entity’s VLC transmitter would encode data into light signals, such as LED light pulses. These signals can carry information such as location, status, and identity, thereby enabling communication between vehicles and infrastructure nodes. The generated data from VLC communication, including digital identities and relevant information, would be securely stored on a blockchain. As VLC communication can be affected by environmental factors, it is crucial to use a consensus mechanism to validate the accuracy of any transmitted data [148].
Digital identities can be associated with corresponding VLC devices through a process known as device registration. During registration, each VLC device is assigned a unique identifier that serves as its digital identity. When a VLC device is powered on and initiates communication, it broadcasts its digital identity along with its operational parameters, which allows receiving devices to recognize and establish an association with the first device. This association enables secure and accurate communication between VLC devices within the network [149].
The proposed architecture aims to intelligently identify the security implementation requirements and ensure security, as per the dominating domain out of all the CIA3 domains. In particular, it is observed that authentication is a holistic requirement. However, other domains switch their dominance according to the infrastructure and the participating entities. The design of the proposed architecture is pictorially depicted in Figure 6. The effectiveness of the proposed architecture must be evaluated using a combination of technical testing, evaluation against established metrics, user feedback, and validation through the academic and research community. In this review, the architecture has been proposed as a novel approach that demonstrates the potential to provide a secure, privacy-preserving, and efficient solution for 6G networks in the context of dynamic security requirements of FL and blockchain-enabled V2X communication.
F. Key Advantages of Proposed Architecture
The proposed architecture, which combines blockchain and FL technologies for secure intelligent networks in 6G communication, offers several key advantages over traditional architectural models:
1) Improved Privacy
One of the primary advantages of this architecture is enhanced privacy. Traditional architectural models may involve centralized data storage and processing, which can pose risks to data privacy. In the proposed architecture, FL allows multiple entities to collaborate on training machine learning models without sharing their sensitive data across the entire network. This decentralized approach minimizes the exposure of data to potential security breaches and enhances privacy.
2) Customization and Adaptability
This architecture allows for the real-time modification of security settings and protocols through FL. Each entity can adjust the blockchain implementation based on its specific needs and requirements, ultimately resulting in a more customized and optimized network. This adaptability is crucial in addressing the dynamic security requirements of 6G communication.
3) Efficient Resource Utilization
Traditional blockchain implementations can pose challenges related to resource utilization, including computing power, storage, and network bandwidth. The proposed architecture aims to optimize the blockchain based on features extracted from V2X communication systems, such as the number of vehicles, perceived threats, available resources, and more. This optimization helps ensure that both resource allocation and data processing are carried out efficiently.
4) Enhanced Data Integrity and Security
This architecture leverages blockchain’s decentralized and tamper-resistant nature to ensure data integrity and security in V2X communications. The combination of blockchain and FL enables real-time updates and model refinements to adapt to changing conditions, thus enhancing the overall system efficiency and responsiveness.
5) Interoperability
This architecture facilitates interoperability between different blockchain networks by allowing entities to collaborate on machine learning models without sharing their data. This enables cross-chain collaborations and data sharing, which can enhance interoperability between different blockchain networks.
6) Unique Digital Identities
The fact that the architecture uses unique digital identities for vehicles and infrastructure nodes, which are associated with VLC transmitters and securely stored on the blockchain, helps it distinguish between and track entities. This can improve the accuracy and security of VLC communication.
7) Flexibility Based on Domains
The proposed architecture intelligently identifies the security implementation requirements and adapts based on the dominating domain within the CIA3 (Confidentiality, Integrity, Authentication, Availability, Access Control) framework. This flexibility ensures that the security measures will be tailored to the specific needs and conditions of different domains.
Future Research Directions
After conducting the detailed overview of the existing research landscape as described in the above sections under the scope of secure V2X in 6G networks, the subsequent paragraphs identify potential challenges and future research directions that require the efforts of both academia and industry to overcome these challenges.
A. V2X-Enabled 6G Network Privacy in 3D Fog Computing
The implementation of 6G-enabled 3D fog computing will require the deployment of unconventional heterogeneous infrastructure to support the massive amounts of data and extremely low latency connectivity involved in such applications [150]. The 6G-enabled 3D fog computing for V2X communication would require a highly complex network infrastructure with multiple layers of communication nodes to enable seamless connectivity. This would require significant investments in infrastructure and maintenance to ensure that the network can handle the high volume of data transmission. This infrastructure will require a scalable, reliable, and secure design [151]. Similarly, with the massive amounts of data that will be generated by 6G-enabled 3D fog computing, it will be essential to develop effective security measures and data management to avoid vulnerabilities and cyber threats [152]. With the huge expansion in the use of connected devices, security is expected to become a major challenge for 6G-enabled 3D fog computing for V2X communication. Hackers will likely seek to exploit vulnerabilities in the system, which can result in data breaches or network failures. Ensuring data privacy and security in this scenario requires robust security measures at all levels of the network. Therefore, there is a need for future research to develop algorithms and tools to process and analyze the security strength of V2X 3D fog computing in 6G.
B. V2X 6G Network Privacy in Augmented Reality
Augmented reality (AR) is a technology that can potentially enhance V2X communication and provide drivers with real-time conceivable data of the road infrastructure and vehicles around them, such as road conditions, traffic signs, and hazards, displayed directly in their field of view, without obstructing their view of the road. AR overlays real-time digital information on top of the physical environment, which may involve sensitive or personal information [22]. To ensure privacy, 6G-enabled V2X communication with AR should provide secure and privacy-protected data transmission, processing, and storage. 6G-enabled V2X communication with AR requires a robust security mechanism to protect the data transmitted between vehicles and infrastructure elements, as well as the AR devices. This includes securing the communication channel, authentication, encryption, and intrusion detection and prevention. As augmented reality becomes more prevalent in V2X communication, it will become increasingly essential to develop privacy-enhancing technologies to protect sensitive information [153]. Future research could focus on developing new technologies, such as secure multi-party computation, homomorphic encryption, and differential privacy, to ensure data privacy. Future research could also focus on developing new trust models and mechanisms that can effectively manage trust in the complex and dynamic AR enabled V2X environment.
C. Secure SDN Architecture in V2X 6G Network
SDN-enabled architecture relies on a centralized controller to manage the network and enforce security policies. This creates a single point of failure and may increase the vulnerability of the network to various types of attacks [154]. Moreover, SDN-enabled secure architecture may face scalability issues when deployed in large-scale V2X networks. As the network grows, it becomes increasingly complex to manage security policies and ensure secure communication, which may limit the scalability of SDN-based security solutions [155]. Similarly, SDN is a relatively new technology, and security measures for SDN are still being developed. Conventional security measures that are available for traditional networks do not apply to the SDN-based architecture in a V2X 6G network, resulting in a gap in security measures that needs to be addressed [156]. Moreover, the lack of standards can lead to inconsistencies in security measures and complicate compatibility between different systems. V2X communication involves the exchange of sensitive information, such as location data and personal identification. With a growing number of devices and entities in the V2X network, it becomes increasingly challenging to ensure secure authentication and access control. Therefore, it is important to develop secure and scalable mechanisms for security frameworks to fulfill the requirements of CIA3 model in SDN-enabled V2X networks.
D. V2X Physical Layer Security in THz Spectrum
The accurate estimation of channel parameters is essential for achieving secure V2X communication. However, the presence of obstacles, reflections, and multipath fading can lead to channel estimation errors, which attackers can use to exploit the security of the communication network [157]. Similarly, V2X communication relies on wireless signals, which can easily be jammed or interfered with, thus leading to disruption or complete breakdown of the communication [158]. Attackers can use jamming or interference to prevent legitimate communication or force the communication to take a less secure route [159]. V2X communication relies on several physical layer techniques such as beamforming, MIMO, and OFDM, which can be vulnerable to attacks such as spoofing, frequency jamming, and injection attacks. These attacks can lead to data manipulation, interception, or destruction [160]. Future research is needed to explore new MIMO beamforming algorithms that can optimize the transmission of secure V2X signals while minimizing the impact of interference. Similarly, the development of new methods for channel modeling and estimation could improve the efficiency and security of MIMO-based V2X communication.
E. V2X and SUMO (Simulation of Urban Mobility)
It is feasible to integrate a security architecture based on both blockchain and FL into the SUMO (Simulation of Urban MObility) simulator, though it demands careful attention to several critical aspects. First, incorporating FL mechanisms within SUMO enables decentralized model training using data from various sources, thus enhancing privacy and efficiency. Secondly, integrating blockchain protocols ensures secure and tamper-proof data sharing among connected vehicles and infrastructure. This decentralized trust model enhances data integrity and prevents unauthorized modifications [161]. Lastly, it is essential to design a simulated V2X communication infrastructure within SUMO to accurately emulate real-world interactions, as this would allow for the testing and refinement of the security architecture in a controlled environment. This endeavor necessitates a comprehensive approach that seamlessly integrates FL, blockchain, and V2X components to effectively address the complexities of urban mobility security [162].
F. Intrusion Detection in V2X Using AI
In the context of V2X communications, leveraging machine learning techniques for anomaly detection, intrusion detection, and security analytics holds great promise. To effectively detect and mitigate emerging threats and attacks, a combination of supervised and unsupervised models should be employed. Supervised models, such as convolutional neural networks (CNNs) and recurrent neural networks (RNNs), can learn from labeled data to recognize known attack patterns. Unsupervised models like autoencoders and generative adversarial networks (GANs) can capture anomalies by learning the normal behavior of V2X communications as well as identifying deviations from them [163]. A hybrid approach integrating both types of models would enable the system to detect and respond to both known and unknown threats, which would ultimately enhance the robustness of the security framework. However, the primary challenge involved in developing such an approach would be the availability of real-life datasets for optimally training the AI models.
Key Lessons Learned
The main lessons learned from this study involve the recognition of the potential of 6G communication for vehicular networks, understanding the security challenges, and analyzing innovative solutions like blockchain and FL through discussions on a generic architecture. The following subsections provide discussions on the several key lessons that have been learned in this study related to 6G communication for vehicular networks and its associated challenges.
A. Transformative Potential of 6G
The study highlights the importance of recognizing the transformative potential of 6G communication for vehicular networks. This implies that it is essential to understand the significant advancements and capabilities that 6G can bring to V2X communication, as these are expected to have a profound impact on the transportation and automotive industry. 6G, which is the next generation of wireless technology, can revolutionize vehicular communication in several ways: First, it underscores the importance of keeping pace with technological advancements, as 6G is poised to bring unprecedented capabilities in specific communication domains including, eMBB, SURLLC, UCDC, BigCom, and 3DCom.
Secondly, recognizing 6G’s potential emphasizes the need to invest in research and development. To harness the full benefits of 6G, it is crucial to conduct research into its applications and security challenges. This lesson highlights the importance of continual innovation and exploration in the field of telecommunications and vehicular networks. Further, understanding the transformative potential of 6G for vehicular networks also highlights the need for cross-disciplinary collaboration. Engineers, computer scientists, and transportation experts must work together to fully leverage 6G’s capabilities. In other words, multidisciplinary approaches are expected to play a crucial role in addressing the complex challenges posed by 6G in V2X communication.
B. Understanding Security Challenges
This study emphasizes the importance of understanding the security challenges posed by the expansion of V2X communication in the 6G era. As technology advances, it also introduces new vulnerabilities and risks that must be thoroughly comprehended to develop effective security solutions. One of the primary lessons of the current work is that the security challenges in 6G vehicular networks are multifaceted and constantly evolving. As technology advances, so do the tactics of malicious actors. It is therefore crucial to accordingly remain adaptive in security measures. The lessons learned by scrutinizing 6G security challenges include the need for continuous monitoring, enhanced threat intelligence, and the ability to adjust security protocols in real-time. Security Information and Event Management (SIEM) systems, anomaly detection algorithms, and real-time monitoring tools are expected to play particularly vital roles in identifying and mitigating security breaches.
C. Need for Innovative Approaches
The rapid advancements in 6G technology will demand innovative solutions to fully harness its transformative potential. Vehicular networks stand to benefit immensely from the low-latency, high-bandwidth capabilities of 6G. Secondly, the conventional methods used to ensure the confidentiality, integrity, and availability of data may no longer suffice in the 6G era. This is where innovative technologies like FL and blockchain will come into play. In particular, FL will enable collaborative machine learning without compromising sensitive data, while blockchain will provide a secure and decentralized ledger for managing transactional data.
Through the integration of these technologies, it is possible to create an unconventional security architecture that not only safeguards V2X communication but also minimizes compromises regarding legitimate users and network services. To effectively address the security challenges involved in 6G V2X communication, it is deemed necessary to use an unconventional security architecture. This architecture should incorporate blockchain and FL to mitigate risks while ensuring the continuity of legitimate users and network services. This study suggests an innovative architecture that can be used to emphasize the possibility for the joint utilization of blockchain and Federated Learning. Blockchain is proposed to be implemented as a technology that can help create a secure and decentralized ledger to manage transactional data, while FL is recommended for collaborative machine learning tasks that keep sensitive data localized. These solutions aim to enhance the security of V2X communication in 6G networks.
D. Proactive Security Measures
This study underscores the significance of proactively implementing security measures to ensure the safety and integrity of V2X communication. It is not ideal to simply wait for security breaches to occur; instead, it is essential to take a proactive approach to security in the 6G era. The integration of advanced technologies such as Federated Learning, which allows collaborative machine learning while preserving data privacy, and blockchain, which provides a secure and decentralized ledger, can significantly enhance the security of vehicular networks in the 6G era. These technologies enable not only data protection but also the creation of trust and transparency in transactions. It is also critical to maintain a deep understanding of the complex security challenges and unconventional risks that come with 6G V2X communication.
E. Addressing Challenges Related to CIA3
This study has mentioned that the security challenges encompass issues related to CIA3, which stands for Confidentiality, Integrity, Availability, Authenticity, and Accountability. These are crucial aspects for ensuring the overall security of vehicular networks in the 6G era. It is paramount to protect sensitive data and ensure that it remains confidential. The lessons learned include the need to encrypt and securely store V2X communication data, thereby ensuring that only authorized entities have access to it. The data exchanged in V2X communication must remain unchanged and trustworthy. The lessons here highlight the importance of data validation mechanisms, specifically in terms of ensuring data has not been tampered with during transmission or storage. For Vehicular Networks to function effectively, data and services must be readily available. The lesson here is to design systems that are resilient to disruptions as well as capable of providing continuous service, even in the face of attacks or failures. It is essential to verify the authenticity of communication participants and data sources. The key lessons involve implementing robust authentication mechanisms to ensure that only legitimate entities can participate in the network. Incorporating FL and Blockchain into 6G Vehicular Networks presents innovative solutions to address these CIA3 challenges. FL allows machine learning to occur on decentralized and localized data sources, thereby preserving data confidentiality and integrity. Blockchain technology provides a secure and immutable ledger for transactional and authentication data, which ultimately enhances data authenticity and accountability.
Conclusion
In conclusion, as 6G communication emerges and expands, it brings with it the potential for massive connectivity between almost everything, including vehicles. To keep up with the radical changes of the 6G era, vehicles and their specific concepts, such as CAVs, IoV, intra-vehicular communication, and V2V communication, will require technological advancements and modernization. However, this expansion of V2X communication will also introduce security risks and vulnerabilities that will need to be addressed. As technology continues to evolve and expand, new security risks and vulnerabilities may arise, and it will be essential to develop new and improved security solutions to mitigate these risks. Altogether, this paper has provided an overview of the security challenges and solutions for V2X communication in the upcoming 6G era. It has discussed the architecture and standards utilized in V2X communication and analyzed V2X security in the CIA3 domains, which include confidentiality, integrity, availability, authentication, and access control. Finally, this paper has highlighted the challenges involved in and future research directions for the domain of the security of V2X communications in the 6G era.