Enabling Tree-Based Hierarchical Authentication and Dynamic Key Update in Intelligent Transportation Systems

Abstract

With the rapid development of vehicular ad hoc networks (VANETs), cross-domain authentication and session key negotiation have become indispensable to ensure communication security. This article proposes a tree-based hierarchical authentication and dynamic key update protocol in intelligent transportation systems (ITSs). In particular, each user locally logs into the on-board unit with a smart card, password, or biometric information. Each user authenticates with the roadside unit (RSU) and makes mutual key negotiation for subsequent secure communication. RSU could act as a proxy to execute secure access control for cross-domain cloud storage data query, avoiding direct interaction between users and clouds. By devising a binary tree group key mechanism, the protocol supports frequent entry and exit of vehicles. Upon member alteration, dynamic group key synchronization and update are executed in a lightweight manner, which significantly mitigates online maintenance costs while guaranteeing both forward and backward security. The protocol reduces online dependence on the trusted authority (TA), achieving identity-anonymous traceability and on-demand accountability. Theoretical security analysis and experimental evaluation demonstrate that the protocol has outstanding advantages in terms of dynamism, privacy protection, and system scalability, which are suitable for practical VANETs deployment with limited resources in ITSs.