Abstract In recent years, privacy research has been gaining ground in vehicular communication technologies. Collecting data from connected vehicles presents a range of opportunities for industry and government to perform data analytics. Although many researchers have explored some privacy solutions for vehicular communications, the conditions to deploy them are still maturing, especially when it comes to privacy for sensitive data aggregation analysis. In this work, we propose a hybrid solution combining the original differential privacy framework with an instance-based additive noise technique. The results show that for typical instances we obtain a significant reduction in outliers. As far as we know, our paper is the first detailed experimental evaluation of differentially private techniques applied to traffic monitoring. The validation of the proposed solution was performed through extensive simulations in typical traffic scenarios using real data.

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.

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.

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.

The consumer electronics industry is witnessing a surge in Internet of Things (IoT) devices, ranging from mundane artifacts to complex biosensors connected across disparate networks. As the demand for IoT devices grows, the need for stronger authentication and access control mechanisms is greater than ever. Legacy authentication and access control mechanisms do not meet the growing needs of IoT. In particular, there is a dire need for a holistic authentication mechanism throughout the IoT device life-cycle, namely from the manufacturing to the retirement of the device. As a plausible solution, we present Authentication of Things (AoT), a suite of protocols that incorporate authentication and access control during the entire IoT device life span. Primarily, AoT relies on Identity- and Attribute-Based Cryptography to cryptographically enforce Attribute-Based Access Control (ABAC). Additionally, AoT facilitates secure (in terms of stronger authentication) wireless interoperability of new and guest devices in a seamless manner. To validate our solution, we have developed AoT for Android smartphones like the LG G4 and evaluated all the cryptographic primitives over more constrained devices like the Intel Edison and the Arduino Due. This included the implementation of an Attribute-Based Signature (ABS) scheme. Our results indicate AoT ranges from highly efficient on resource-rich devices to affordable on resource-constrained IoT-like devices. Typically, an ABS generation takes around 27 ms on the LG G4, 282 ms on the Intel Edison, and 1.5 s on the Arduino Due.