Adaptive certificate distribution mechanism in vehicular networks using variable inter-certificate refresh period

A method for distributing digital certificates in a vehicle-to-vehicle network, said method comprising:

• establishing wireless communications between two vehicles in the vehicle-to-vehicle network, where a first vehicle is transmitting messages and a second vehicle is receiving messages;
• measuring performance of the vehicle-to-vehicle network as a function of network and configuration parameters, where the network and configuration parameters are allowed to vary throughout their permissible range;
• employing a digital certificate by the first vehicle, where the digital certificate contains information which can be used to verify the authenticity of messages sent by the first vehicle over the vehicle-to-vehicle network;
• creating a certificate digest by the first vehicle, where the certificate digest is a hash function of the digital certificate;
• measuring current network conditions by the first vehicle;
• defining a value of an variable inter-certificate refresh period to optimize the performance of the vehicle-to-vehicle network based on the measured current network conditions by the first vehicle, said variable inter-certificate refresh period being the number of message packets in a set, where the last message packet in the set includes the digital certificate and all previous message packets in the set include the certificate digest;
• transmitting message packets over the vehicle-to-vehicle network by the first vehicle, where the message packets contain message data and either the digital certificate or the certificate digest as dictated by the variable inter-certificate refresh period;
• receiving the message packet by the second vehicle, and determining if the message packet contains the digital certificate or the certificate digest;
• verifying the message packet by the second vehicle if the message packet contains the digital certificate, or if the message packet contains the certificate digest and a matching digital certificate for the certificate digest has previously been received;
• storing the message packet by the second vehicle if the message packet contains the certificate digest and the matching digital certificate for the certificate digest has not previously been received, and if storage space is available;
• dropping the message packet by the second vehicle if the message packet contains the certificate digest and the matching digital certificate for the certificate digest has not previously been received, and if storage space is not available;
• and
• using the message data in the message packet, if the message packet is verified, in an application by the second vehicle.

A distribution system for distributing digital certificates in a vehicle-to-vehicle network, said distribution system comprising:

• a first vehicle in the vehicle-to-vehicle network;
• a first application system in the first vehicle, where the first application system contains information about the first vehicle to be provided to other nearby vehicles in the form of message data;
• a first communication system in the first vehicle, where the first communication system includes a controller configured to select a value for a variable inter-certificate refresh period and determine whether to send a digital certificate or a certificate digest, and a transmitter for transmitting message packets containing the message data and either the digital certificate or the certificate digest;
• a second vehicle in the vehicle-to-vehicle network;
• a second communication system in the second vehicle, where the second communication system includes a receiver for receiving the message packets and separating the message packets into the message data and either the digital certificate or the certificate digest, and a processor configured to validate the certificate digests with the digital certificates which are received;
• and
• a second application system in the second vehicle, where the second application system processes the message data after validating the digital certificate or the certificate digest for each message packet.