CPPA-SKU: Towards efficient conditional privacy-preserving authentication protocol with secret key update in VANET

Abstract

The rapid development of intelligent transportation systems (ITS) has raised higher requirements for traffic data sharing and collaboration. As an effective solution, vehicular ad-hoc network (VANET) has emerged to support real-time data transfer between vehicles and infrastructure. However, VANET faces the challenges of data security and privacy. To alleviate these, many conditional privacy-preserving authentication (CPPA) schemes have been proposed. CPPA utilizes signature technology to ensure message authenticity while enabling the effective tracing of malicious vehicles. Unfortunately, traditional CPPA schemes fail to consider the security of secret keys stored in tamper-proof devices (TPDs). Additionally, most existing schemes still suffer from excessive computational and communication overhead. In this paper, we propose CPPA-SKU, an efficient CPPA scheme with message recovery for VANET. CPPA-SKU introduces a secret key update method using a secure pseudo-random function and Shamir’s secret sharing to prevent key leakage issues in TPDs. Additionally, CPPA-SKU enables the recovery of relevant messages, eliminating the need to embed messages in signatures, thereby reducing the communication overhead. Furthermore, CPPA-SKU is implemented based on the elliptic curve cryptosystem, which avoids expensive bilinear pairing operations while ensuring the security of signatures. We also formally prove the security of CPPA-SKU in the random oracle model. Comprehensive performance evaluations indicate that CPPA-SKU reduces computational overhead by approximately 1.3$\times$–2.8$\times$ and communication overhead by approximately 1.5$\times$-3.5$\times$.