What is a contract certificate?
A contract certificate is a digital certificate used in ISO 15118 Plug & Charge to link an electric vehicle to a driver’s charging contract with an e-mobility service provider (eMSP). It contains the contract’s e-mobility account identifier (EMAID) and a public key. The vehicle proves that it holds the matching private key, and that is how it authenticates automatically at compatible charge points.
Contract certificates let drivers start charging without presenting an RFID card or opening an app. They are issued by the eMSP, or by a Plug & Charge service acting for it, and they form part of the public key infrastructure (PKI) behind ISO 15118 Plug & Charge authentication. Plug & Charge is the driver experience; the contract certificate is the credential behind it.
How does a contract certificate work?
- Establishing a contract. The driver activates Plug & Charge with an eMSP, usually in its app. The eMSP links the contract and its EMAID to the vehicle’s provisioning identity, the certificate the manufacturer installed at the factory.
- Issuing and installing the certificate. The eMSP, or a Plug & Charge service on its behalf (the certificate provisioning service, or CPS, in ISO 15118 terms), obtains a signed contract certificate and delivers it to the vehicle, through a compatible charge point or through the manufacturer’s backend. Charge points relay the installation over OCPP: natively in OCPP 2.0.1, and in OCPP 1.6 with the Open Charge Alliance’s ISO 15118 extension.
- Authenticating at the charge point. When the driver plugs in, the vehicle presents its contract certificate and proves possession of the matching private key. The charge point and its management platform validate the certificate (its chain, expiry and revocation status, the last usually checked by the platform over OCSP) and check that the eMSP contract is authorized. Once authorization succeeds, charging begins, and the session is billed according to the driver’s contract.
- Managing the certificate lifecycle. Contract certificates have defined validity periods. The eMSP manages their renewal and revocation. If a certificate expires or is revoked, the driver needs a valid replacement or another authorization method the charge point supports.
Under ISO 15118-20, a compatible vehicle can hold contract certificates from several eMSPs and present the one the charge point accepts.
The certificates in a Plug & Charge PKI
| Certificate | Who issues it | Where it lives | What it proves |
|---|---|---|---|
| Root certificate authority (CA) certificate | A root operator such as Hubject (V2G root), or an OEM or eMSP root | The trust stores of the participants that rely on it | The anchor that the other certificates chain to |
| OEM provisioning certificate | The vehicle manufacturer | The vehicle, from production | The vehicle’s identity (PCID, its provisioning certificate identifier), used to request a contract certificate |
| Contract certificate | The eMSP’s sub-CA | The vehicle | That the vehicle holds a contract (EMAID) with that eMSP |
| Charge point (SECC, the charger’s communication controller) certificate | A sub-CA under the V2G root, at the request of the CPO or its platform | The charge point | That the charge point is genuine, during the TLS handshake |
Not every participant trusts every root. Which chains apply depends on the Plug & Charge ecosystem the eMSP and the charge point operator (CPO) have joined.
Why it matters for CPOs and eMSPs
For eMSPs, the contract certificate is what identifies and bills a Plug & Charge customer automatically. They must arrange certificate issuance, provisioning and lifecycle management, either with their own infrastructure or through a specialized Plug & Charge service provider.
For CPOs, supporting Plug & Charge requires compatible charging hardware with its own charge point certificates, certificate validation in the management platform and a backend able to authorize the driver’s eMSP contract. In practice that means a way to authorize the contract: typically a Plug & Charge service such as Hubject’s, a roaming connection or a direct agreement with the eMSP. Open protocols such as Hubject’s OPCP and CharIN’s OPNC let Plug & Charge service providers exchange certificate data across PKI ecosystems.
How AMPECO supports Plug & Charge
AMPECO is a certified Hubject Plug&Charge backend provider. CPOs and eMSPs on AMPECO’s EV charging management platform can offer certificate-based authentication through Hubject’s Plug & Charge services, as described on AMPECO’s Hubject integration page. On the charger side, the platform implements the OCPP 2.0.1 ISO 15118 functions, which carry certificate installation and updates.
AMPECO’s guide to ISO 15118 for CPOs and eMSPs explains the PKI and how Plug & Charge certificates pass through OCPP.
Frequently asked questions
Is a contract certificate the same as an EMAID?
No. The EMAID is the identifier of the contract, a string the eMSP assigns and that appears in the session record. The contract certificate is the credential that proves the vehicle holds that contract: it contains the EMAID and a public key, and it is issued under the eMSP’s sub-CA, run by the eMSP or by a service provider.
How long is a contract certificate valid?
Contract certificates have defined validity periods set by the applicable PKI rules and the issuer; CharIN’s PKI guide recommends that one should not outlast the vehicle’s provisioning certificate. An expired or revoked certificate has to be replaced before Plug & Charge works again for that vehicle.
Will a contract certificate work at any Plug & Charge charger?
No. The charge point must support ISO 15118 Plug & Charge, recognize the certificate’s trust chain and be able to authorize the driver’s eMSP contract. That usually means a Plug & Charge service, a roaming connection or a direct agreement between the providers. A valid chain proves who issued the contract; it does not tell the CPO who will pay for the session.
Related terms
- Plug and Charge Technology
- ISO 15118
- ISO 15118-20
- OPCP (Open Plug & Charge Protocol)
- OCPP (Open Charge Point Protocol)
- e-Mobility Service Provider (eMSP)
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