Abstract-Modern vehicles are no longer mere mechanical devices; they comprise dozens of digital computing platforms, coordinated by an in-vehicle network, and have the potential to significantly enhance the digital life of individuals on the road. While this transformation has driven major advancements in road safety and transportation efficiency, significant work remains to be done to support the security and privacy requirements of the envisioned ecosystem of commercial services and applications (i.e., Internet access, video streaming, etc.). In the era when "service is everything and everything is a service", Vehicular Communication (VC) systems cannot escape from this ongoing trend towards multi-service environments accessible from anywhere. To meet the diverse requirements of vehicle operators and Service Providers (SPs), we present SEROSA, a service-oriented security and privacy-preserving architecture for VC. By synthesizing existing VC standards and Web Services (WS), our architecture provides comprehensive identity and service management while ensuring interoperability with existing SPs. We fully implement our system and extensively assess its efficiency, practicality, and dependability. Overall, SEROSA significantly extends the state of the art and serves as a catalyst for the integration of vehicles into the vast domain of Internet-based services.

Energy efficiency has been the driving force behind the design of communication protocols for battery-constrained wireless sensor networks (WSNs). The energy efficiency and the performance of the proposed protocol stacks, however, degrade dramatically in case the low-powered WSNs are subject to interference from high-power wireless systems such as WLANs. In this paper we propose COG-MAC, a novel cognitive medium access control scheme (MAC) for IEEE 802.15.4-compliant WSNs that minimizes the energy cost for multihop communications, by deriving energy-optimal packet lengths and single-hop transmission distances based on the experienced interference from IEEE 802.11 WLANs. We evaluate COG-MAC by deriving a detailed analytic model for its performance and by comparing it with previous access control schemes. Numerical and simulation results show that a significant decrease in packet transmission energy cost, up to 66%, can be achieved in a wide range of scenarios, particularly under severe WLAN interference. COG-MAC is, also, lightweight and shows high robustness against WLAN model estimation errors and is, therefore, an effective, implementable solution to reduce the WSN performance impairment when coexisting with WLANs.

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Efficient communication in the crowded ISM band requires the communication networks to be aware of the networking environment and to control their communication protocols accordingly. In this paper we address the issue of efficient WSN communication under WLAN interference. We propose analytic models to describe the WLAN idle time distributions as observed by the WSN nodes, together with efficient methods for parameter estimation. We evaluate how the spectrum sensing capability of the sensors affects the performance of the idle period distribution estimation and conclude that the proposed solutions are accurate enough to support cognitive WSNs. © 2012 IEEE

Standardization and harmonization efforts have reached a consensus towards using a special-purpose Vehicular PublicKey Infrastructure (VPKI) in upcoming Vehicular Communication (VC) systems. However, there are still several technical challenges with no conclusive answers; one such an important yet open challenge is the acquisition of shortterm credentials, pseudonym: how should each vehicle interact with the VPKI, e.g., how frequently and for how long? Should each vehicle itself determine the pseudonym lifetime? Answering these questions is far from trivial. Each choice can affect both the user privacy and the system performance and possibly, as a result, its security. In this paper, we make a novel systematic effort to address this multifaceted question. We craft three generally applicable policies and experimentally evaluate the VPKI system performance, leveraging two large-scale mobility datasets. We consider the most promising, in terms of efficiency, pseudonym acquisition policies; we find that within this class of policies, the most promising policy in terms of privacy protection can be supported with moderate overhead. Moreover, in all cases, this work is the first to provide tangible evidence that the state-of-the-art VPKI can serve sizable areas or domain with modest computing resources.