Eichrecht – Signed Meter Values

Eichrecht – Signed Meter Values

This resource is for e-mobility service providers (EMSPs) and EV drivers who wish to see how much electricity was supplied in a particular charge session. 
In accordance with the German calibration law (Mess-und Eichrecht), charge point operators may be required to provide signed meter data to EMSPs and drivers, so they can verify these values against the information displayed on the invoice for that charge session.   

GreenFlux offer software for  Charge Point Operators (CPO) to manage a network of charge stations. In this capacity, we facilitate the exchange of Signed Meter Values through networks and provide instructions to support users in understanding and processing the information provided by CPOs. 

Short description 

A charge station with a calibrated meter will produce digitally signed (encrypted) meter values. These encrypted meter values cannot be manipulated by a third party. With the help of ‘ Transparency software’ , users can decrypt the meter values and compare them against the values that have been charged to them.  

To verify that the right amount of electricity has been charged, users need to know: 

  • The encrypted data (“signed_data”) 
  • The decryption key (“public_key”) 
  • The encryption method (“encoding_method”) 
  • Where to find and download the transparency software (“url”)

Signed Data file 

GreenFlux provides this data a JSON format via URL in the CDRs. Below is an example of a Signed Data for a charging session. 

Please note that different manufacturers may apply different formats and do not use all fields. 

EIchrecht Signed Data File
FieldData availableDescription
Session IDAvailableID of the charging session
EVSE_IDAvailableID of the EVSE (unique Connector of  charge station) 
Encoding MethodOptionalDepending on the manufacturer, the encoding method might differ. More information below 
Encoding method version OptionalVersion of the Encoding Method 
Public keyOptionalThe key required for decryption. May be part of the message or needs to be looked up elsewhere 
NatureAlwaysIndicates the metervalues for start and end of a charging session 
Plain dataOptionalThe unencrypted metervalues 
Signed dataAlwaysThe relevant encrypted/signed data 
URLOptionalThe URL where the decryption software can be downloaded 

How to decrypt 

Please follow the URL in the Signed Data File to go to the website of the Transparency Software. Follow the instructions provided by the provider of the software. 

Public Key 

I n most cases, the “public_key” is not provided through the Signed Data file. The public key then can be retrieved either: 

Manufacturers may have their own transparency software or use a software implemented by multiple companies. 

Below is a list of relevant Encoding Methods known to GreenFlux.  

Encoding methodSoftwareURL
Alfen Eichrecht Alfen Eichrecht encoding / implementation https://alfen.com/de/downloads
OCMF Proposed by S.A.F.E https://www.safe-ev.de/de/transparenzsoftware.php
EDL40 E-Mobility Extension Proposed by S.A.F.E https://www.safe-ev.de/de/transparenzsoftware.php
EDL40 Mennekes Mennekes implementation https://www.safe-ev.de/de/transparenzsoftware.php

Please note that GreenFlux is not responsible for the availability and usability of these transparency software suppliers.

For questions, please contact the manufacturer or Charge Point Operator directly. 

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