An Efficient Secure Service Discovery Protocol for Intelligent Transportation Systems ∗ Kaouther Abrougui Azzedine Boukerche PARADISE Research Laboratory, DIVA Research Center, University of Ottawa, Canada Email:{abrougui, boukerch}@site.uottawa.ca Abstract—The number of applications in Intelligent Trans- portation Systems (ITS) is growing rapidly. Vehicular systems have been widely seen as a promising technique for ITS-based applications. Two main types of applications are considered in vehicular systems: safety and infotainment applications. While the first type of applications provides drivers with warning or alert messages to prevent them from an accident or a disaster, the second type of applications allows drivers and passengers to localize services, get information, and even perform transactions with the surrounding services. Thus, it is very important to have secure discovery and communication with these services, while not affecting drastically the communication delay and the network scalability. In this paper, we discuss the importance of secure service discovery and communication in vehicular systems. Then, we propose a secure service discovery protocol for vehicular systems dedicated mainly to the infotainment type of application. We discuss the security requirements achieved by the proposed protocol and we report on its performance evaluation. I. I NTRODUCTION The number of applications in Intelligent Transportation Systems (ITS) is growing rapidly. Vehicular systems have been widely seen as a promising technique for ITS-based applications. Two main types of applications are considered in vehicular systems: safety and infotainment applications. While the first type of applications provides drivers with warning or alert messages to prevent them from an accident or a disaster, the second type of applications allows drivers and passengers to localize services, get information, and even perform transactions with the surrounding services. Thus, it is very important to have secure discovery and communication with these services, while not affecting drastically the communication delay and the network scalability. Ensuring security during service discovery in vehicular systems is very important [11]. Drivers, passengers and roadside components would like to share their services in a safe and secure communication environment. As a result, service discovery in vehicular systems requires efficient models in order to guarantee the security and confidentiality of road users. In this paper, we discuss the importance of secure service discovery and communication in vehicular systems. Then, we propose a novel secure service discovery and communication protocol for vehicular systems dedicated to the convenience type of applications. We focus on the authentication aspect since this latter is very important for guaranteeing the security during service discovery. The remainder of this paper is organized as follows: Section 2 presents the related works. Section 3 presents the threat model. Section 4 presents our proposed secure service discovery proto- col. Section 5 discusses the security requirements achieved by our proposed protocol. Section 6 presents our simulation experiments. Finally, section 7 concludes the paper and presents our future work. *This work is partially supported by Canada Research Chair Program, NSERC, Ontario Distinguished Research Award Program, PREA/ Early Research Award, and OIT/MRI fund. II. RELATED WORKS In Vehicular Ad Hoc Networks (VANets), the security and mainly authentications schemes could be either relying on Road Side Units (RSUs), or not relying on RSUs. Therefore, we classify secure service discovery in VANets in two main categories: (i) infrastructure- based secure service discovery; and (ii) infrastructure-less secure service discovery. In the following, we describe the protocols in each category. The authentication of infrastructure-based secure service discovery protocols can be performed through a public key cryptography [7], [12], [13] or symmetric key [4], [6]. Tsang et a. presented in [12] a Peer-to-Peer Anonymous Authen- tication (PPAA) system that can be applied to VANets. Their system handles the privacy of clients and servers. They claim that in VANets, there is a need to protect driver’s location and privacy such that two drivers that are communicating to each other are anonymous among the neighboring cars. Moreover, authentication must be established in order to distinguish the malicious road components from the legitimate ones. The failure in guaranteeing security in VANets is very critical, because the traffic could be paralyzed and many accident could be incurred. The proposed PPAA system involves two main entities: (i) the group manager, and (ii) peers, where these latter could be clients or servers. Clients wants to access services in the VANet, and servers should provide the clients with their requested services in a private and secure environment. Calandriello et al. discussed in [7] the problem of pseudonym- based authentication. They design their schemes while guaranteeing the reduction in the security overhead. They use the group key concept for the generation of the public and private key pairs in a vehicle. Lin et al. presented in [13], a secure and privacy preserving mechanism based on Group Signature and Identity-based Signature techniques. They call their system GSIS. Their group-signature-based mechanism permits the reduction of the cost induced by the storage of the public and private key pairs and decreases the consumption of the bandwidth needed for the transmission of the certificate revocation list. The proposed protocol permits as well to retrace back a sender of a message by the authorized agencies. Zhang et al. presented in [6] a message authentication scheme called RAISE. Their scheme is based on roadside units. In their protocol, message authentication verification is performed trough the roadside units. They use the k-anonymity in order to guarantee the privacy of users. They proposed a variant that works with the absence of roadside units. Their proposed scheme has low computation and communication overhead. Wasef et al. presented in [4] a privacy preserving group com- munications protocol for vehicular ad hoc networks (PPGCV). The proposed protocol uses a probabilistic key distribution concept and relies on a security threshold mechanism. It is based on group communications and guarantees the confidentiality of users informa- tion. The proposed PPGCV has the property of being stateless in computing a new key and updating the compromised ones under the condition that the number of revoked nodes does not bypass a certain value. 2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications 978-1-4577-1348-4/11/$26.00 ©2011 IEEE 756