Copra: Conditional pseudonym resolution algorithm in VANETs

Wireless communication between vehicles is protected by digital certificates but these certificates and related identifiers must not be usable to track vehicles. Therefore, short-term pseudonymous certificates are applied and regularly changed in order to protect the driver's privacy. But in well defined situations, e.g. network attacks or traffic accidents, it should be possible to retrieve the appropriate long-term identifier from the certificate issuer. Hence, the resolution of pseudonym identifiers is a balancing act between full privacy and uncontrolled access to long-term identifiers. We propose a generic pseudonym resolution protocol that can be applied by network infrastructure entities to request pseudonym resolution information only under defined conditions. It is shown that the protocol is balanced and flexible to be applied for different use cases (e.g. lawful interception or misbehavior detection). In contrast to related protocols our solution does not increase pseudonym certificate size and avoids additional overhead and delay in the certificate acquisition phase. Further, a new feature is proposed that enables the infrastructure entities to validate the stated reason for the desired pseudonym resolution before respective information is provided. Measurements from field operational test implementations show the feasibility and practicability of the protocol when applying misbehavior detection in wireless vehicular communication networks.