Security and privacy of current Car-to-X systems heavily depends on the usage of pseudonym certificates. These carry the required information for authenticating messages received from other vehicles. However, only a limited amount of detailed studies about certificate distribution strategies in VANETs as well as attack surfaces of such systems has been proposed. Therefore, a general study about possible distribution mechanisms and their parametrization is provided in this work. Thereby, the management of entries in request lists is identified as a key issue for system performance. Additionally, a design flaw in the currently standardized ETSI ITS distribution scheme is outlined leading to the possibility of an attacker significantly increasing channel load on the safety critical control channel. A solution to this problem is suggested and an evaluation of its performance is provided. Furthermore, the evaluation shows the great influence of request list management on authentication delay and thus on security inducted packet loss.

Wireless intelligent transport systems based on Carto-X communication technology are about to enter the mass market in upcoming years. Thereby, efficient and reliable security systems are a core point of concern in system design. Currently regarded digital signature schemes using pseudonym certificates can introduce significant overhead into the highly bandwidth restricted system. Thus, mechanisms to optimize the efficiency of the security mechanisms in regard to authentication delay and channel load are required. Prior work has focused on scenarios with high node mobility, e.g., freeways. However, bandwidth conserving mechanisms are also required for urban low and medium mobility scenarios to enable foreseen extension of the wireless network for the many other volatile road users like pedestrians. Hence, an approach for efficient pseudonym certificate distribution in urban scenarios is provided in this work. The given simulation based environment shows that it can enhance cooperative awareness while limiting used bandwidth. Thus, it can be regarded as well suitable for future urban intelligent transport systems.

Car-to-X communication systems, often called vehicular ad-hoc networks (VANETs), are in the process of entering the mass market in upcoming years. Thereby, security is a corepoint of concern due to the intended use for safety critical driver assistance systems. However, currently suggested security mechanisms introduce significant overhead into Car-to-X systems in terms of channel load and delay. Especially, the usage of on the fly distributed pseudonym certificates leads to a trade off between channel load and authentication delay, which may lead to significant packet loss. Thus, this work studies a novel concept for pseudonym certificate distribution in VANETs using rate-adaptive certificate distribution based on monitoring a vehicle’s environment. Thereby, the cyclic certificate emission frequency is adapted on the fly based on cooperative awareness metrics for discrete parts of the vehicle’s surrounding. The obtained mechanism is evaluated in a highway as well as an urban simulation scenario to show its suitability for a broad range of traffic conditions. Thereby, we find that it is able to significantly outperform the currently standardized approach for pseudonym certificate distribution in VANETs based on ETSI ITS standards. Thus, it should be regarded for further development of future VANETs