BECSI: Bandwidth efficient certificate status information distribution mechanism for VANETs

Abstract

Certificate revocation is a challenging task, especially in mobile network environments such as vehicular ad Hoc networks (VANETs). According to the IEEE 1609.2 security standard for VANETs, public key infrastructure (PKI) will provide this functionality by means of certificate revocation lists (CRLs). When a certificate authority (CA) needs to revoke a certificate, it globally distributes CRLs. Transmitting these lists pose a problem as they require high update frequencies and a lot of bandwidth. In this article, we propose BECSI, a Bandwidth Efficient Certificate Status Information mechanism to efficiently distribute certificate status information (CSI) in VANETs. By means of Merkle hash trees (MHT), BECSI allows to retrieve authenticated CSI not only from the infrastructure but also from vehicles acting as mobile repositories. Since these MHTs are significantly smaller than the CRLs, BECSI reduces the load on the CSI repositories and improves the response time for the vehicles. Additionally, BECSI improves the freshness of the CSI by combining the use of delta-CRLs with MHTs. Thus, vehicles that have cached the most current CRL can download delta-CRLs to have a complete list of revoked certificates. Once a vehicle has the whole list of revoked certificates, it can act as mobile repository. © 2013 - IOS Press and the authors. All rights reserved.