Design and Implementation of Secret Key Agreement for Platoon-based Vehicular Cyber-Physical Systems

TL;DR

This paper presents CoopKey, a cooperative secret key agreement scheme for vehicular platoons that uses channel randomness to generate shared encryption keys, enhancing communication security in dynamic environments.

Contribution

It introduces a novel cooperative key agreement method based on channel quantization, optimized via dynamic programming, and validated through real-world experiments with autonomous vehicles.

Findings

CoopKey achieves low secret key mismatch rates in various settings.

Generated keys pass all NIST randomness tests.

System scalability impacts performance, as shown in simulations.

Abstract

In platoon-based vehicular cyber-physical system (PVCPS), a lead vehicle that is responsible for managing the platoon's moving directions and velocity periodically disseminates control messages to the vehicles that follow. Securing wireless transmissions of the messages between the vehicles is critical for privacy and confidentiality of platoon's driving pattern. However, due to the broadcast nature of radio channels, the transmissions are vulnerable to eavesdropping. In this paper, we propose a cooperative secret key agreement (CoopKey) scheme for encrypting/decrypting the control messages, where the vehicles in PVCPS generate a unified secret key based on the quantized fading channel randomness. Channel quantization intervals are optimized by dynamic programming to minimize the mismatch of keys. A platooning testbed is built with autonomous robotic vehicles, where a TelosB wireless node is used for onboard data processing and multi-hop dissemination. Extensive real-world experiments demonstrate that CoopKey achieves significantly low secret bit mismatch rate in a variety of settings. Moreover, the standard NIST test suite is employed to verify randomness of the generated keys, where the p-values of our CoopKey pass all the randomness tests. We also evaluate CoopKey with an extended platoon size via simulations to investigate the effect of system scalability on performance.