Cross-Certificate Mechanism for EV Charging Interoperability

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Solution Overview

Problem

Existing electric vehicle charging systems face challenges in authenticating users and managing trust relationships between different vehicle-to-grid (V2G) root certificate authorities, leading to vulnerabilities and inconvenience in accessing charging infrastructure across different regions.

Innovation Solution

A cross certification method and apparatus that enables electric vehicles to verify certificate chains using cross certificates issued by trusted V2G root CAs, allowing interoperability and flexible trust management in the EV charging network.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single V2G root CA is used for certificate verification, then security and trust management is simplified, but interoperability between different charging operators and regions is limited

Engineering Contradiction:
ImproveinteroperabilityVSAvoidtrust management
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces a cross-certification mechanism where a first V2G root CA issues a cross certificate that is recognized by a second V2G root CA. This cross certificate acts as an intermediary that bridges trust between different V2G operators, allowing EVs trusting the second root CA to access charging infrastructure operated by the first root CA without requiring direct trust relationships between all parties.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The cross certificate issued by the first V2G root CA serves multiple functions: it enables the first root CA to issue certificates that are trusted by the second root CA, allows EVs to verify certificates from different operators, and facilitates seamless interoperability across regional boundaries while maintaining individual operator autonomy.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If EVs store multiple root CA certificates for different regions, then access to charging infrastructure across regions is enabled, but memory usage and verification complexity increase

Engineering Contradiction:
Improvecross-region accessVSAvoidstored certificates
Core Design Contradiction:
Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

Instead of requiring EVs to store multiple root CA certificates from different regions, the system uses a cross certificate as an intermediary. The EV only needs to trust its home region's root CA, and the cross certificate mechanism automatically enables access to other regions through the established trust relationship between root CAs.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If frequent certificate updates are implemented, then security is maintained, but system stability and operational convenience are reduced

Engineering Contradiction:
ImprovesecurityVSAvoidsystem stability
Core Design Contradiction:
ReliabilityVSStability of the object's composition

Solution Approach 1:

The cross certificate is issued in advance by the first V2G root CA and establishes a long-term trust relationship. This preliminary action eliminates the need for frequent updates, as the cross certificate remains valid until its expiration date, providing both security and system stability simultaneously.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP4712015A2Cross-certificate method and device for electric vehicle charging
Publication Date: 2026.03.18 HYUNDAI MOTOR CO LTD
  • EP4712015A2 patent drawingFigure 1~2
  • EP4712015A2 patent drawingFigure 3
  • EP4712015A2 patent drawingFigure 4A~5

AI summary

A cross-certificate method is performed by an electric vehicle (EV) for being supplied with power from electric vehicle supply equipment (EVSE) associated with a charging point operator (CPO) having established a trust relationship with a first vehicle to grid (V2G) root certificate authority (rootCA) and a second V2G root certificate authority. The cross-certificate method may include steps of: requesting charging from the electric vehicle supply equipment; receiving, from the electric vehicle supply equipment, a certificate chain held by the electric vehicle supply equipment; and verifying whether or not a last certificate of the certificate chain has been signed by the second V2G root certificate authority, wherein the last certificate of the certificate chain can be a cross-certificate issued by the second V2G root certificate authority.