Vehicular Public Key Infrastructure Research Articles

SECMACE+: Upscaling Pseudonymous Authentication for Large Mobile Systems

The central building block of secure and privacy-preserving Vehicular Communication (VC) systems is a Vehicular Public Key Infrastructure (VPKI), which provides vehicles with multiple anonymized credentials, termed pseudonyms. These pseudonyms are used to ensure VC message authenticity and integrity while preserving vehicle (thus passenger) privacy. In the light of emerging large-scale multi-domain VC environments, the efficiency of the VPKI and, more broadly, its scalability are paramount. By the same token, preventing misuse of the credentials, in particular, Sybil-based misbehavior, and managing “honest-but-curious” VPKI entities are other facets of a challenging problem. In this paper, we leverage the state-of-the-art VPKI system and enhance its functionality towards a highly-available, dynamically-scalable, and resilient design; this ensures that the system remains operational in the presence of benign failures or resource depletion attacks, and that it dynamically scales out, or possibly scales in, according to request arrival rates. Our full-blown implementation on the Google Cloud Platform shows that deploying large-scale and efficient VPKI can be cost-effective: the processing latency to issue 100 pseudonyms is approximately 56 ms. More so, our experiments show that our VPKI system dynamically scales out or scales in according to the rate of pseudonyms requests. We formally assess the achieved security and privacy properties for the credential acquisition process. Overall, our scheme is a comprehensive solution that complements standards and can catalyze the deployment of secure and privacy-protecting VC systems.

A Privacy-Preserving and Transparent Identity Management Scheme for Vehicular Social Networking

Vehicular social networking is expected to become a reality soon, where secure and privacy-preserving identity management is a prerequisite. Various organizations and studies have recommended using Vehicular Public-key Infrastructure (VPKI) to securely and privately manage vehicles' identities. However, the existing VPKI schemes still do not deal with identity management in vehicular social networking. In this work, we propose a Privacy-Preserving Identity Management (PPTIM) scheme for vehicular social networking to securely and privately manage vehicles' social identities. PPTIM builds on the transparency log (distributed ledger) proposals for web PKI, but it addresses challenges specific to vehicular social networking. All pseudo-social identities, pseudonym certificates issued against pseudo-social identities, revocation process, and revocation status validation are conducted on a transparency log. With an efficient data structure named the Accumulation Tree (AT), we extend the conventional transparency log to offer trustworthy pseudonym certificate validation without relying on the Certificate Revocation Lists (CRLs). In addition, PPTIM strengthens the security of vehicular social networking by protecting vehicles to a greater extent from being duped by malicious pseudonym certificates through logging and constant monitoring. Finally, performance and security analysis show the cost-effectiveness and security of PPTIM.

Survey on Issues and Recent Advances in Vehicular Public-Key Infrastructure (VPKI)

Public-key infrastructure (PKI) provides the essential foundation for public-key cryptography, and security is often bootstrapped from a PKI. Standardization bodies, organizations, researchers, and experts reached a consensus that deploying Vehicular PKI (VPKI) can ensure the security and privacy requirements of Cooperative Intelligent Transportation Systems (C-ITS). Given the importance of VPKI, researchers and experts have worked to ensure VPKI meets the high security and privacy requirements of C-ITS. This survey focuses on VPKI schemes designed to securely and privately manage and revoke public-key certificates in three parts. The first part presents evaluation metrics that help to compare the existing VPKI proposals systematically. The second part classifies VPKI schemes and provides an overview of each. The third part focuses on observations made using the evaluation metrics through a systematic comparison of VPKI schemes. Finally, suggestions for future VPKI research are presented.

Accountable credential management system for vehicular communication

Social Internet of Vehicles (SIoV) is becoming a reality where private and secure communication is a prerequisite. Various standardization organizations and studies have reached a consensus to use Vehicular Public-key Infrastructure (V-PKI) in order to secure SIoV systems. However, significant security- and trust-related problems remain unsolved. This study presents an Accountable Credential Management System (ACMS) for vehicular communication to solve these problems. ACMS builds on transparency log (Distributed ledger technology) schemes for web PKI but addresses the challenges specific to vehicular communication. ACMS transparently handles certificate-related use cases, namely, certificate provision, registration, validation, and revocation. It also enhances the security of vehicular communication through constant monitoring; hence, assuring that no pseudonym certificate is accepted by vehicles before being logged and witnessed. With an efficient data structure known as the Accumulation Tree (AT), we extend the conventional transparency log to provide a cost-effective and trustworthy authentication process without relying on certificate revocation lists. Time cost and performance analyses show that the proposed approach is feasible and scalable than existing V-PKI schemes. Moreover, using Tamarin Prover, it is verified that our proposed technique provides defense against an active adversary.

Schnorr-Based Implicit Certification: Improving the Security and Efficiency of Vehicular Communications

In the implicit certification model, the process of verifying the validity of the signer's public key is combined with the verification of the signature itself. When compared to traditional, explicit certificates, the main advantage of the implicit approach lies in the shorter public key validation data. This property is particularly important in resource-constrained scenarios where public key validation is performed very often, which is common in vehicular communications (V2X) that employ pseudonym certificates. In this article, we show an alternative Schnorr-based implicit certification procedure that can improve the efficiency of a popular V2X-oriented Vehicular Public Key Infrastructure (VPKI), the Security Credential Management System (SCMS). As an additional contribution, we show that SCMS's underlying certificate provisioning procedure, based on butterfly keys, is vulnerable to existential forgery attacks under certain conditions. We then discuss how this issue can be fixed in an effective and efficient manner.

Privacy-Preserving Certificate Linkage/Revocation in VANETs Without Linkage Authorities

Vehicular communication (V2X) technologies are expected to become common in the future, providing better efficiency and safety in transportation. This envisioned large-scale deployment, however, critically depends on addressing some issues. In special, to prevent abuse by drivers, messages exchanged among authorized vehicles must be authenticated. This implies the need of a Vehicular Public Key Infrastructure (VPKI). Unlike traditional PKIs, though, VPKIs are also expected to preserve the privacy of honest drivers, preventing their vehicles from being easily identified or tracked. One promising VPKI solution, which copes with such requirements and is among the main candidates for standardization in the United States, is the Security Credential Management System (SCMS). In this paper, aiming to enhance and address shortcomings identified in SCMS, we provide two main contributions. First, we describe and fix two birthday attacks against SCMS's certificate revocation process, thus improving the system's long-term privacy. Second, we propose a method that simplifies SCMS's architecture, removing the need for Linkage Authorities (LAs); this approach cuts down deployment costs while reducing the system's attack surface, in particular against some troublesome forms of replay attacks that are hereby unveiled.

ACPC: Efficient revocation of pseudonym certificates using activation codes

Vehicular communication (V2X) technologies allow vehicles to exchange information about the road conditions and their own status, and thereby enhance transportation safety and efficiency. For broader deployment, however, such technologies are expected to address security and privacy concerns, preventing abuse by users and by the system’s entities. In particular, the system is expected to enable the revocation of malicious vehicles, e.g., in case they send invalid information to their peers or to the roadside infrastructure; it should also prevent the system from being misused for tracking honest vehicles. Both features are enabled by Vehicular Public Key Infrastructure (VPKI) solutions such as Security Credential Management Systems (SCMS), one of the leading candidates for protecting V2X communication in the United States. Unfortunately, though, SCMS’s original revocation mechanism can lead to large Certification Revocation Lists (CRLs), which in turn impacts the bandwidth usage and processing overhead of the system. In this article, we propose a novel design called Activation Codes for Pseudonym Certificates (ACPC), which can be integrated into SCMS to address this issue. Our proposal is based on activation codes, short bit-strings without which certificates previously issued to a vehicle cannot be used by the latter, which are periodically distributed to non-revoked vehicles using an efficient broadcast mechanism. As a result, the identifiers of the corresponding certificates do no need to remain on the CRL for a long time, reducing the CRLs’ size and streamlining their distribution and verification of any vehicle’s revocation status. Besides describing ACPC in detail, we also compare it to similar-purpose solutions such as Issue First Activate Later (IFAL) and Binary Hash Tree based Certificate Access Management (BCAM). This analysis shows that our proposal not only improves privacy (e.g., in terms of resilience against colluding system authorities), but also leads to processing and bandwidth overheads that are orders of magnitude smaller than those observed in the state of the art.

Certificate revocation in vehicular ad hoc networks techniques and protocols: a survey

Vehicular Ad hoc Networks (VANETs) are special kind of Mobile Ad hoc Networks (MANETs), where vehiclescommunicate with each other in ad hoc formation. VANETs consist of Vehicles and Road Side Units (RSUs) that assist inthe network management. Vehicles communicate with each other and RSUs, with the aim to provide infotainment and safety services on road. Security is an important consideration in VANETs as safety of humans (passengers) is an important issue. Vehicular Public Key Infrastructure (VPKI) is an adapted form of Public Key Infrastructure (PKI) used to achieve the key management and security services in VANETs. Certificate generation and revocation is one of the primary functions of VPKI. Certificate revocation is used for revoking the malicious nodes and terminate their access rights to the network. In this paper we classify revocation schemes in a novel way into centralized and decentralized manners. This paper covers a survey of different certificate revocation schemes, and provides an overview of the research in the area of certificate revocation in VANETs.

VPKI Hits the Highway: Secure Communication for the Connected Vehicle Program

This article presents a condensed account of the 10-year effort to develop and deploy vehicular public-key infrastructure (VPKI) as a security infrastructure for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) intelligent transportations systems (ITS). The author discusses the ways in which government, industry, and academia have converged to bring the promise of vehicular networks as ITS into the reality of the 21st century.

SECMACE: Scalable and Robust Identity and Credential Management Infrastructure in Vehicular Communication Systems

Several years of academic and industrial research efforts have converged to a common understanding on fundamental security building blocks for the upcoming vehicular communication (VC) systems. There is a growing consensus toward deploying a special-purpose identity and credential management infrastructure, i.e., a vehicular public-key infrastructure (VPKI), enabling pseudonymous authentication, with standardization efforts toward that direction. In spite of the progress made by standardization bodies (IEEE 1609.2 and ETSI) and harmonization efforts [Car2Car Communication Consortium (C2C-CC)], significant questions remain unanswered toward deploying a VPKI. Deep understanding of the VPKI, a central building block of secure and privacy-preserving VC systems, is still lacking. This paper contributes to the closing of this gap. We present SECMACE, a VPKI system, which is compatible with the IEEE 1609.2 and ETSI standards specifications. We provide a detailed description of our state-of-the-art VPKI that improves upon existing proposals in terms of security and privacy protection, and efficiency. SECMACE facilitates multi-domain operations in the VC systems and enhances user privacy, notably preventing linking pseudonyms based on timing information and offering increased protection even against honest-but-curious VPKI entities. We propose multiple policies for the vehicle–VPKI interactions and two large-scale mobility trace data sets, based on which we evaluate the full-blown implementation of SECMACE. With very little attention on the VPKI performance thus far, our results reveal that modest computing resources can support a large area of vehicles with very few delays and the most promising policy in terms of privacy protection can be supported with moderate overhead.

The Key to Intelligent Transportation: Identity and Credential Management in Vehicular Communication Systems

Vehicular communication (VC) systems will greatly enhance intelligent transportation systems. But their security and the protection of their users' privacy are a prerequisite for deployment. Efforts in industry and academia brought forth a multitude of diverse proposals. These have now converged to a common view, notably on the design of a security infrastructure, a vehicular public-key infrastructure (VPKI) that shall enable secure conditionally anonymous VC. Standardization efforts and industry readiness to adopt this approach hint at its maturity. However, there are several open questions remaining, and it is paramount to have conclusive answers before deployment. In this article, we distill and critically survey the state of the art for identity and credential management in VC systems, and we sketch a road map for addressing a set of critical remaining security and privacy challenges.

Defense against Sybil attack in the initial deployment stage of vehicular ad hoc network based on roadside unit support

ABSTRACTIn this paper, we propose two certificate mechanisms for preventing the Sybil attack in a vehicular ad hoc network (VANET): the timestamp series approach and the temporary certificate approach. We focus on an early‐stage VANET when the number of smart vehicles is only a small fraction of the vehicles on the road and the only infrastructure components available are the roadside units (RSUs). Our approach does not require a dedicated vehicular public key infrastructure to certify individual vehicles but RSUs are the only components issuing certificates. The vehicles can obtain certificates by simply driving by RSUs, without the need to pre‐register at a certificate authority. The timestamp series approach exploits the fact that because of the variance of the movement patterns of the vehicles, it is extremely rare that the two vehicles pass by a series of RSUs at exactly the same time points. The vehicles obtain a series of certificates signed by the RSUs, which certify their passing by at the RSU at a certain time point. By exploiting the spatial and temporal correlation between vehicles and RSUs, we can detect the Sybil attack by checking the similarity of timestamp series. In the temporary certificate‐based approach, an RSU issues temporary certificates valid only in a particular area for a limited time. To guarantee that each vehicle is assigned only a single certificate, at the issuance of the first certificate, it is required that the RSU physically authenticate the vehicle. When driving by the subsequent RSUs, however, the certificate can be updated in a chained manner. By guaranteeing that each vehicle is issued a single certificate in a single area, the Sybil attack is prevented. We provide mathematical analysis and simulation for the timestamp series approach. The simulation shows that it works with a small false‐positive rate in simple roadway architecture. Copyright © 2013 John Wiley & Sons, Ltd.