Token-based Vehicular Security System (TVSS): Scalable, Secure, Low-latency Public Key Infrastructure for Connected Vehicles

TL;DR

The paper tackles secure, scalable vehicular public key infrastructure (VPKI) for connected and autonomous vehicles, addressing the latency and revocation challenges of centralized schemes. It introduces Token-based Vehicular Security System (TVSS), an edge-based VPKI that shifts PC generation to roadside units (RSUs) and uses tokens issued by a certificate authority (CA) to obtain pseudonym certificates (PCs) locally, enabling rapid authentication even with brief RSU contact. TVSS features a formal security framework for anonymity, unlinkability, and unforgeability, introduces a clone-attack defense, and proposes region-based revocation with local CRLs and token backlogs to drastically reduce communication and revocation overhead. Real-world field tests on a TVSS-enabled network show substantial improvements in PC generation latency (up to $28.5\times$ faster than SECMACE and $38.5\times$ faster than SCMS), improved PC refresh reliability at highway speeds, and much smaller PCRLs, indicating meaningful impact for scalable, privacy-preserving VPKI in urban-to-highway deployments.

Abstract

Connected and Autonomous vehicles stand to drastically improve the safety and efficiency of the transportation system in the near future while also reducing pollution. These systems leverage communication to coordinate among vehicles and infrastructure in service of a number of safety and efficiency driver assist and even fully autonomous applications. Attackers can compromise these systems in a number of ways including by falsifying communication messages, making it critical to support security mechanisms that can operate and scale in dynamic scenarios. Towards this end, we present TVSS, a new VPKI system which improves drastically over prior work in the area (including over SCMS; the US department of transportation standard for VPKI). TVSS leverages the idea of unforgeable tokens to enable rapid verification at the road side units (RSUs), which are part of the road infrastructure at the edge of the network. This edge based solution enables agile authentication by avoiding the need for back-end servers during the potentially short contact time between a moving vehicle and the infrastructure. It also results in several security advantages: (1) Scalable Revocation: it greatly simplifies the revocation problem, a difficult problem in large scale certificate systems; and (2) Faster Refresh: Vehicles interact more frequently with the system to refresh their credentials, improving the privacy of the system. We provide a construction of the system and formally prove its security. Field experiments on a test-bed we develop consisting of on-board units (OBUs) and RSUs shows substantial reduction in the latency of refreshing credentials compared to SCMS, allowing the system to work even with smaller window of connectivity when vehicles are moving at higher speeds. Notably, we are able to execute the bottleneck operation of our scheme with a stationary RSU while traveling at highway speeds .

Figures (14)

• Figure 1: Simplified SCMS and TVSS architectures.
• Figure 2: Overview of all protocols of TVSS.
• Figure 3: Our new hash chain mechanism.
• Figure 4: VPKI Security Game
• Figure 5: Winning Conditions.

Theorems & Definitions (1)

• Definition 1