Low-risk Privacy-preserving Electric Vehicle Charging with Payments

and ordering requests and offers.Furthermore, some protocols propose blockchain technology for handling the payment.However, the proposed protocols often (i) do not cover customer privacy to a full extent; (ii) do not allow for combined bidding and payment transfer with limited risk for both, the EV and the charging station; and (iii) do not cover both, gridto-vehicle and vehicle-to-vehicle charging.Due to limited trust and anonymity in privacy-preserving systems, there is also a substantial financial risk for both, the EV (or the consumer in general) and the charging station (or the producer in general).While the EV runs the risk of paying without receiving a sufficient amount of energy (or any energy at all), the charging station runs the risk of providing energy and not receiving sufficient compensation.This is largely unaddressed in prior work.Following a privacy-preserving protocol for grid-to-vehicle charging presented in [11], in this paper, we present a comprehensive protocol for EV charging with payments.The protocol preserves the privacy of all participants and the location privacy of the EVs during the exploration and bidding phase.Furthermore, pseudonymity is preserved during the charging phase and the payment phase, and a parameter is proposed which allows for controlling risk.Two different implementations for transferring installments in exchange for energy are described and evaluated.These implementations are compared in terms of risk, scalability, performance and privacy.The rest of this paper is structured as follows: Section II describes EV charging, blockchain technology, hash timelocked contracts and state channels.Section III describes the proposed privacy-preserving protocol.Section IV evaluates the protocol with respect to risk, privacy and scalability.Section V provides an overview of related work.Section VI summarizes this paper. II. BACKGROUNDThis section summarizes the relevant background for EV charging and blockchain technology. A. Electric Vehicle ChargingOne of the most common types of EVs relies on batteries which need to be recharged from an electric power source [15].Depending on their capacity and usage, these batteries may retain significant portions of their initial charge over longer periods of time.Three different types of charging can be distinguished [15], [20]: (i) G2V (Grid-to-Vehicle) Charging:The EV is charged by the power grid.This is the most common case and is usually done via a charging station, see e.g., [15]