Chargy is a transparency software for secure and transparent e-mobility charging processes, as defined by the German "Eichrecht". The software allows you to verify the cryptographic signatures of energy measurements within charge detail records and comes with a couple of useful extentions to simplify the entire process for endusers and operators.
As a driver of electric vehicles you have to tacle a couple of well-known challenges: Where and when do I charge my vehicle and will I receive a correct invoice for this process? To solve these issues the German Eichrecht defines a legal foundation how to measure time and energy in a trustworthy way, how to sign and store these measurments via digital signatures and how to send these data to the endusers. You can think of this as a digital receipt of the charging time, amount of consumed energy and the resulting costs. Later in time an enduser can use a so called "transparency software" to verify the correctness of these receipts and to prove possible mistakes.
Although the high demands of correctness and transparency in e-mobility charging seem to be obvious, surprisingly no Open Source transparency software was available until now. By this the goal of transparency was actually not achieved, as even experienced endusers can not distinguish between a wrong receipt and bugs within a closed source transparency software. In the same way the legal situation of consumers had not been improved significantly.
It is the legal duty of a charging station vendor and operator to provide all the required tools to verify a receipt. Chargy is a such a tool and helps endusers to understand the origin and composition of all expenses independend of their desktop computer and smart phones. For special regulatory tasks even a special Chargy Linux-Live-DVD exists.
| Roll | Description | Expectations |
|---|---|---|
| EV Drivers | A simple and vendor independent way to understand and verify their charging costs. | |
| Open Source Community | Initiative of GraphDefined, chargeIT mobility and Wiedergrün | Providing an open and standardized solution. |
| PTB (Working Group 8.51 Metrology Software) | National Metrology Institute of the Federal Republic of Germany | Regulatory verification of the software according to PTB-A 50.7, Abschnitt 3.1.1.3 Buchstabe B and published here. |
| Charging Station Vendors | Responsible for regulatory issues | Data models and protocols for the verification of charging processes. |
| Charging Station Operators | Responsible for technical and legal issues | Providing a common software for the verification of charging processes to e-mobility providers. Might act on behalf of multiple charging station owners. |
| E-Mobility Providers | The legal person selling energy to ev drivers | Providing a common software for the verification of charging processes to their customers. Might want to include the software into their own software stack. |
Chargy exists within a highly regulated environment. The following constraints exists.
| Constraint | Description, Background |
|---|---|
| Support of Linux-, Mac OS X and Windows-Desktop-Operating Systems | The software must run on Windows 10+ and Mac OS X. Aditionally it must run on Linux, in order to provide Live-DVD or USB-Stick. |
| Support on iOS- and Android Smart Phone-Operating Systems | The software muss run on current iOS and Android smart phones. |
| Limited cryptography | Most charging station vendors only support a single elliptic curve cryptography algorithm, e.g. secp192r1 and export only public keys instead of digital certificates of charging stations. |
| Constraint | Description, Background |
|---|---|
| Frozen Versions | The cryptographic hash value of a specific version of the software is part of a legal document. Automatic updates without user interaction is not possible. |
| Smart Meter Regulations | Some charging station vendors implement their requirements via smart meters. Therefore additional regulatory requirements occur. |
| Accessibility | Charging station owners might be public sector bodies which have to support EU directive 2016/2102 on the accessibility of websites and mobile applications. |
By using the well-known frameworks Apache Cordova and Electron we created a platform independent and Open Source transparency software. This software can process the (still) very different data formats of different charging station providers and verify their correctness by using cryptographic algorithms. Besides this, Chargy is the first transparency software in the market which does not only implement the minimal requirements of the German regulators like the Physikalisch-Technische Bundesanstalt (PTB), but tries to put the enduser into the center of any development. This means Chargy does not only show additional information about charging stations, their geo coordinates, addresses, tariffs and includes an issue tracker. This all is done to give the ev driver the best experience, to help him evaluate the correctness of the charging process and to support him when something seems to be wrong.
The following architecture describes the entities, actors and data flows.
| Entity | Description |
|---|---|
| Charging Station Operator | The operator of charging stations selling energy to EV drivers. |
| EV Driver | An enduser who wants to charge its electric vehicle at a charging station and understand the resulting costs. |
| Charging Station | A device to charge an electric vehicle. Will record and digitaly sign the energy consumption measurements. |
| Charge Transparency Record | A data record about the charging process including at least charging time, consumed energy and a digital signature. May include additional signed or unsigned metadata to support the ev driver. |
| Public Key(s)/Certificates | The charging station operator publishes its charging stations within a public register. |
| Public Charging Station Register | The charging station register acts as trusted source of charging station metadata, esp. public keys for the verification of charge transparency records. |
The following describes the data processing and verification steps within the transparency software.
