Private Metering in EV Charging Infrastructure: An OCPP Extension

The security of electrical vehicle (EV) charging systems has been improving over the past years. However, privacy concerns are yet to be addressed as profiling attacks can be accomplished on EV charging meter readings. This paper proposes a new communication protocol that preserves the privacy of users while retaining the aggregate metering values to be used by the EV charging management system. The proposed protocol extends the existing Open Charge Point Protocol (OCPP) specifications. OCPP is an open and widely used protocol for EV chargers but it provides no privacy-preserving mechanisms. Differential privacy concepts are applied in the proposed paper along with key masking to hide private data from different kinds of adversaries. A lightweight implementation of the proposed approach is implemented and tested on a hardware testbed to ensure the practicality of the implemented system. Experimental results and analysis show that this method is able to preserve the confidentiality of metering values with minimal computation.

I. Introduction

With the continuous growth of the global EV market, the need for EV chargers has been significantly increasing. By 2021, about 1.8 million charging points were reported to be available publicly where 500,000 of them were installed in 2021 [1]. Given such rapid growth, concerns related to security and privacy on those EV chargers started to rise. Different organizations and companies have been working to develop specifications to ensure reliable and secure communication of the EV charging infrastructure. When it comes to EV chargers management and communication, the Open Charge Point Protocol (OCPP) is a widely accepted specification followed by many companies around the globe [2]. OCPP is a publicly published specification by the Open Charge Alliance (OCA) [2]. The specification describes the protocol used to manage the communication between charging station network including the EV, the charging station, and the central management system. The first release of OCPP was published in 2015. Newer versions of the protocol then introduced many improvements over the years. The latest version of OCPP as of the time of writing this paper is OCPP 2.0.1. In this version, security aspects of the protocol were addressed like introducing security profiles, secure firmware updates, and security event notifications.