On the RSU-based secure distinguishability among vehicular flows

In the smart cities of the future, people expect to gather data from moving vehicles. Due to the existence of malicious users who claim to be in a traffic flow but actually are in others, a location proof for vehicular trajectory-based data needs to be developed. RoadSide Units (RSUs) are commonly used in smart cities, and a vehicular trajectory's location proof can be generated based on messages collected from RSUs along the trajectory. This paper studies the optimal RSU placement problem: Given a set of traffic flows, the objective is to place a minimum number of RSUs to securely distinguish all flows. A traffic flow is securely distinguishable if the set of its passing RSUs is unique among all traffic flows and unforgeable. To solve this problem, an RSU placement algorithm with an approximation ratio O(ln n) is proposed. In order to further reduce the number of deployed RSUs, this paper explores the credential propagation mechanism via Car-to-Car (C2C) communications, which essentially extend the coverage of an RSU. Approximation algorithms are proposed to solve the problem, and extensive real data-driven experiments demonstrate the efficiency and effectiveness of the proposed algorithms.