An on-board vehicle communication system and method employ a storage device, a communication device and a controller. The storage device is configured to store a plurality of security certificates. The communication device is configured to receive external information that is external to a host vehicle equipped with the on-board vehicle communication system. The controller is configured to determine whether to begin a security certificate replenishment process to attempt to receive additional security certificates from at least one source that is external of the host vehicle based on the received external information, upon an amount of security certificates stored in the storage device decreasing below a first prescribed threshold.