Air quality in urban environments has become a central issue of our present society as it affects the health and lives of the population all over the world. The first step in mitigating negative effects is proper measurement of the pollution level. This work presents a portable air pollution measurement system, built from off-the-shelf devices, that is designed to assure user privacy and data authenticity. Data is collected from sensor modules that can be hand carried or installed on vehicles, possibly leading to a vehicular sensor network that may cover a larger area. The main challenge is to provide authenticity for the sensor data while also ensuring user privacy. The proposed system assures authenticity and non-repudiation for the collected data by using group signatures and a blockchain-like structure for secure storage. We use regular key-exchange protocols based on elliptic curve cryptography in order to securely bootstrap a session key, then we benefit from secure tunneling to export data from sensors to the remote server. Post-update tampering is prevented by the use of a blockchain-like structure on the data server. We carry experiments both to determine the computational requirements of the procedures, as well as to measure indicators of air quality on nearby areas.
Keywords: authentication; group signatures; pollution measurement; security; sensor networks.