Cross-certificate method and device for electric vehicle charging
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.
1 . A method of validating an electric vehicle supply equipment (EVSE) trusting a first root certificate authority (CA) performed by an electric vehicle (EV) to be charged from the EVSE and trusting a second root CA, the method comprising:
initiating communications with the EVSE;
receiving, from the EVSE, a certificate chain of the EVSE including a leaf certificate for the EVSE and a cross certificate issued by the second root CA for a subordinate certificate authority under the first root CA; and
verifying the cross certificate and the leaf certificate for the EVSE based on a root CA certificate issued by the second root CA,
wherein verifying the cross certificate and the leaf certificate for the EVSE comprises:
verifying the cross certificate and the leaf certificate for the EVSE based on the root CA certificate issued by the second root CA without a first root CA certificate issued by the first root CA.
2 . The method of claim 1 , wherein the certificate chain is maintained by the EVSE.
3 . The method of claim 1 , wherein verifying the cross certificate and the leaf certificate for the EVSE comprises:
verifying that a certificate in a highest level in the certificate chain has been signed by the second root CA.
4 . The method of claim 3 , wherein the certificate in the highest level in the certificate chain is the cross certificate.
5 . The method of claim 4 , wherein a public key included in the cross certificate coincides with a public key corresponding to a private key used to issue a certificate in a second highest level in the certificate chain.
6 . The method of claim 5 , wherein the certificate in the second highest level in the certificate chain has been issued by a charge point operator (CPO) associated with the EVSE.
7 . The method of claim 4 , wherein the cross certificate is issued by the second root CA via a cross certification intermediating device.
8 . The method of claim 4 , wherein an expiration date of the cross certificate is set before expiration dates of a first root certificate and a second root certificate whichever is earlier.
9 . The method of claim 4 , wherein the cross certificate comprises a public key of the subordinate certificate authority and a signature generated by signing an identification (ID) of the subordinate certificate authority by the second root CA.
10 . A power transfer method performed by an electric vehicle supply equipment (EVSE) trusting a first root certificate authority (CA), the power transfer method comprising:
receiving a certificate-related request from an electric vehicle (EV) trusting a second root CA;
providing the EV with a certificate chain of the EVSE including a leaf certificate for the EVSE and a cross certificate issued by the second root CA for a subordinate certificate authority under the first root CA;
receiving a verification result for the certificate chain from the EV; and
supplying electric power to the EV based on the verification result,
wherein providing the EV with the certificate chain of the EVSE comprises:
providing the certificate chain ends with an intermediate certificate issued based on a first root CA certificate issued by the first root CA and the certificate chain does not include the first root CA certificate, and
the verification result is determined by the EV without the first root CA certificate.
11 . The power transfer method of claim 10 , wherein a certificate in a highest level in the certificate chain is the cross certificate.
12 . The power transfer method of claim 11 , wherein the certificate in the highest level in the certificate chain has been signed by the second root CA.
13 . The power transfer method of claim 11 , wherein a public key included in the cross certificate coincides with a public key corresponding to a private key used to issue a certificate in a second highest level in the certificate chain.
14 . The power transfer method of claim 13 , wherein the certificate in the second highest level in the certificate chain has been issued by a charge point operator (CPO) associated with the EVSE.
15 . The power transfer method of claim 11 , wherein the cross certificate is issued by the second root CA via a cross certification intermediating device.
16 . The power transfer method of claim 11 , wherein the cross certificate comprises a public key of the subordinate certificate authority and a signature generated by signing an identification (ID) of the subordinate certificate authority by the second root CA.
17 . The power transfer method of claim 10 , wherein the certificate chain is sent to the EV in a ServerHello message during a transport layer security (TLS) handshake operation.