Secure Cooperative Data Downloading in Vehicular Ad Hoc Networks

In this paper, we propose a secure cooperative data downloading framework for paid services in vehicular ad hoc networks (VANETs). In our framework, vehicles download data when they pass by a road side unit (RSU) and then share the data after they travel out of the RSU's coverage. A fundamental issue of cooperative data downloading is how vehicles effectively share data with each other. We develop an application layer data sharing protocol which coordinates the vehicles to relay data for sharing according to their positions. Such coordinated sharing can avoid collisions in the medium access control (MAC) layer and the hidden terminal issue in multi-hop transmissions. A salient feature of the proposed sharing protocol is that it can guarantee the receipt of the requested data file for each applicant vehicle passing a road side unit. Moreover, we also address security and privacy issues in the process of data downloading and sharing, ensuring applicants' exclusive access to the applied data and privacy of the vehicles involved in the application. We carry out NS2 simulations to thoroughly examine the performance of the proposed cooperative downloading protocol implemented over an 802.11p based VANETs.