# Authentication and Billing for Dynamic Wireless EV Charging in an Internet of Electric Vehicles
###### Abstract  
Dynamic wireless charging (DWC) is a promising technology to charge Electric Vehicles (EV) using on-road charging segments (CS), also known as DWC pads. In order to ensure effective utilization of this on-the-road charging service, communication and coordination need to be established between the EVs and the different network entities, thereby forming an Internet of Electric Vehicles (IoEV). In an IoEV, EVs can utilize different V2X communication modes to enable charging scheduling, load management, and reliable authentication and billing services. Yet, designing an authentication scheme for dynamic EV charging presents significant challenges given the mobility of the EVs and the short contact time between the EVs and the charging segments. Accordingly, this work proposes a fast, secure and lightweight authentication scheme that allows only authentic EVs with valid credentials to charge their batteries while ensuring secure and fair payments. The presented scheme starts with a key pre-distribution phase between the charging service company (CSC) and the charging pad owner (PO), followed by a hash chain and digital signature-based registration and authentication phase between the EV and the CSC, before the EV reaches the beginning of the charging lane. These preliminary authentication phases allow the authentication between the EVs and the charging segments to be performed using simple hash key verification operations prior to charging activation, which reduces the computational cost of the EVs and the CS. Symmetric and asymmetric key cryptography are utilized to secure the communication between the different network entities. Analysis of the computational and transmission time requirements of the proposed authentication scheme shows that, for an EV traveling at 60 km/h to start charging at the beginning of the charging lane, the authentication process must be initiated at least 1.35 m ahead of the starting point of the lane as it requires \(\simeq\)81 ms to be completed. Internet of Electric Vehicles (IoEV); dynamic wireless charging (DWC); authentication; billing; cryptography; signature; hashing +
Footnote †: journal: _Future Internet_  
between the EV and the charging socket. This requires effective yet costly electrical isolation solutions to mitigate risks of electrocution, particularly during harsh weather conditions [3]. Furthermore, the need for hardware compatibility and/or interoperability between the EV charging connector and the charging inlet point impacts the convenience of EV users and may contribute to their range anxiety for fear of running out of charge without reaching a compatible charging point [5]. Accordingly, to reduce the risks associated with wired (plug-in) charging and improve charging flexibility and convenience, wireless EV charging solutions are becoming increasingly popular, in which the charging power is wirelessly transferred, typically using inductive coupling, between a primary charging pad laid on the ground and a secondary receiver pad fitted at the bottom of the EVs [6; 7]. Nevertheless, range anxiety remains the key drawback for any stationary charging solution including static wireless charging systems, as EV drivers fear running out of charge before reaching the charging station and/or without completing their desired journeys on time. Dynamic wireless charging (DWC) systems offer an effective solution to the issue of range anxiety. This is because, by laying charging segments in dedicated lanes along extended roadways, EVs can be charged wirelessly during their motion [2; 6; 8]. This ensures charge ubiquity during extended journeys, thereby reducing range anxiety and eliminating driving delays due to the EV charging downtime [9; 10]. Furthermore, large-scale deployments of DWC lanes across different cities enable EV battery downsizing and reduces EV production costs by increasing the dependence on the energy received during the vehicle's motion [11; 12].