Message Authentication and Secret Key Agreement in VANETs via Angle of Arrival
This addresses security challenges in vehicular ad-hoc networks (VANETs) for safety-critical applications, offering an incremental improvement by integrating physical layer techniques with existing protocols.
The paper tackles message authentication and secret key agreement in VANETs by using Angle of Arrival (AoA) estimation to verify message originator locations based on GPS claims, formulating it as a hypothesis testing problem with closed-form performance measures like correct decision and false alarm probabilities. It also extends this to a physical layer assisted secret key agreement protocol that mitigates Man in the Middle attacks by validating physical locations.
In the scope of VANETs, nature of exchanged safety/warning messages renders itself highly location dependent as it is usually for incident reporting. Thus, vehicles are required to periodically exchange beacon messages that include speed, time and GPS location information. In this paper paper, we present a physical layer assisted message authentication scheme that uses Angle of Arrival (AoA) estimation to verify the message originator location based on the claimed location information. Within the considered vehicular communication settings, fundamental limits of AoA estimation are developed in terms of its Cramer Rao Bound (CRB) and existence of efficient estimator. The problem of deciding whether the received signal is originated from the claimed GPS location is formulated as a two sided hypotheses testing problem whose solution is given by Wald test statics. Moreover, we use correct decision, $P_D$, and false alarm, $P_F$, probabilities as a quantitative performance measure. The observation posterior likelihood function is shown to satisfy regularity conditions necessary for asymptotic normality of the ML-AoA estimator. Thus, we give $P_D$ and $P_F$ in a closed form. We extend the potential of physical layer contribution in security to provide physical layer assisted secret key agreement (SKA) protocol. A public key (PK) based SKA in which communicating vehicles are required to validate their respective physical location. We show that the risk of the Man in the Middle attack, which is common in PK-SKA protocols without a trusted third party, is waived up to the literal meaning of the word "middle".