Networked electric-vehicle (EV) charging increasingly depends on advanced metering infrastructure (AMI) for charging authorization, metered-energy reporting, and demand-response control, making authenticated key establishment a safety-relevant communication requirement. This study reconstructs the security-relevant equations of a recently developed elliptic-curve multi-phase authentication protocol and evaluates whether its claimed properties follow from the specified algebra. Six structural weaknesses are identified: reversible exposure of the infrastructure private-key term, long-term key disclosure through the proposed signature equation, replay susceptibility inside the timestamp window, lack of binding between authentication and ephemeral Diffie-Hellman values, dual session-key definitions, and static-identity linkability. Advanced Metering Infrastructure–Secure Multi-Phase Authentication (AMI-SMPA) is designed with signed credentials, transcript-bound ephemeral elliptic-curve Diffie-Hellman, Hash-based Message Authentication Code (HMAC)-based Extract-and-Expand Key Derivation Function (HKDF), role-separated HMAC key confirmation, Advanced Encryption Standard in Galois/Counter Mode (AES-GCM), rotating aliases, and replay-aware state. The protocol is mapped to the EV, EV supply equipment, charging-station controller, smart meter (SM), data concentrator, and utility control center (UCC); it protects station-meter-to-utility metering and charging-control messages without replacing ISO 15118. In an isolated emulator, all four reconstructed attack conditions succeeded in 1,000/1,000 trials, whereas all corresponding AMI-SMPA checks succeeded in 1,000/1,000 trials. A controlled 1,000-run profile estimated 16.92 ms computation time, 19.35 ms end-to-end latency, 612 bytes/session, 4.35 mJ/session, 99.14% packet-delivery ratio, 98.77% replay detection, 98.76% unauthorized message-modification rejection (UMR), and 97.63% key-compromise containment. A fixed-seed, all-at-once EV charging burst model for 50, 200, and 1,000 charging points yielded 60.36–60.46 completed sessions/s, with queue-inclusive mean completion time rising from 423.69 to 8,279.05 ms. These controlled results support protocol-level feasibility and expose capacity-planning requirements; they do not establish operational-network performance or power-grid stability.

Reliable and timely vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication is essential for safety-critical applications in intelligent transportation systems (ITS). Distributed time-division multiple access (TDMA) supports deterministic channel access in vehicular ad hoc networks (VANETs), but contention during slot reservation and mobility-induced merging collisions remain major obstacles to reliable communication under dense and rapidly changing traffic conditions. This study investigates these limitations and proposes a backoff-based partitioned-reservation medium access control protocol (BPR-MAC), a distributed TDMA protocol that integrates reservation-phase contention control with mobility-aware slot allocation. A mini-slot carrier-sensing backoff mechanism was introduced to resolve competing reservation attempts within individual slots, while an adaptive slot-partitioning mechanism was developed to allocate transmission resources according to driving direction and vehicle speed relative to the surrounding traffic stream. The protocol was evaluated using MATLAB-based discrete-event simulations of a 3 km two-way highway, with vehicle speeds ranging from 40 to 120 km/h. Performance was assessed in terms of slot-reservation delay and merging-collision rate under different traffic densities, slot-occupancy conditions, and protocol parameter settings. At 90% two-hop-neighborhood slot occupancy, BPR-MAC reduced the merging-collision rate from 0.778 for a Vehicular Media Access Control (VeMAC)-like baseline to 0.017, a reduction of 97.8%. For 100 vehicles, the reservation delay decreased from approximately 31 to 2 frames. Ablation results showed that mobility-aware slot partitioning accounted for most of the reduction in merging collisions, while reservation-phase backoff provided complementary collision suppression and faster slot acquisition. Sensitivity analysis further showed that the principal performance trends remained stable under moderate variations in the relative-speed threshold and contention-window size. These findings indicate that combining localized contention control with relative-motion-based slot allocation can improve the predictability of distributed channel access in dense vehicular networks. BPR-MAC provides a communication-layer approach to supporting time-sensitive safety messaging and cooperative V2V/V2I communication in ITS.