IPEK: Event-Criticality-Aware Evidential Trust Management against Strategic Insider Attacks in Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks (VANETs) are vulnerable to intelligent attackers who exploit the homogeneous treatment of traffic events in existing trust models. These attackers accumulate reputation by reporting correctly on low-priority events and then inject false data during safety-critical situations---a strategy that current approaches cannot detect because they ignore event severity and location criticality in trust calculations. This paper addresses this gap with IPEK. The proposed system rests on three mechanisms: an asymmetric local trust mechanism in which penalties scale with event and location severity while rewards follow an asymptotic model, making trust difficult to regain after misuse; a DST-based global trust fusion that adopts Yager's combination rule---assigning conflicting evidence to uncertainty rather than forcing premature decisions---together with sequential source-reliability ordering and an asymmetric risk accentuation mechanism; and a strategic attack model, defined for evaluation, that behaves selectively according to event severity and exhibits colluding feedback. Simulations using OMNeT++, Veins, and SUMO compare IPEK against two centralized, threshold-based schemes (MDT and TCEMD) via a detection-threshold sweep. IPEK is the only method able to reduce its false positive rate to as low as 0.44%, whereas the baselines cannot go below roughly 22%. At matched false positive rates, IPEK attains the highest recall at every point (e.g., 0.781 at 5% FPR) and the highest F1-score (0.803) over a broad operating range. Ablation studies confirm that both the Yager rule and event-severity awareness contribute to performance independently. The results demonstrate that integrating context-awareness into both attack modeling and trust evaluation yields a substantially more resilient defense against strategic adversaries than symmetric approaches.