A robust and efficient password-based conditional privacy preserving authentication and group-key agreement protocol for VANETs

With the rapid growth of information and communication technology (ICT) and Internet of things (IoT), the concept of smart-city is recently introduced by the government of many countries to improve the living environment of urban people. In city areas, the numbers of vehicles are increased exponentially day-by-day. Therefore, it is very difficult to control and manage the city traffic caused by tens of thousands vehicles. The Vehicular Ad-hoc Network (VANET) is used to communicate with the vehicles to give alert for weather conditions, road defects, traffic conditions, etc. and the conditions of the vehicle including location, speed, traffic status, etc. Therefore, the traffic efficiency and safety of the vehicles can be improved with the help of VANET. To serve this purpose, in the literature, many conditional privacy preserving authentication (CPPA) protocols based on CA-PKC (certificate authority-based public key cryptography), and ID-PKC (identity-based public key cryptography) have been put forwarded. In addition, some of these CPPA protocols use elliptic curve or bilinear-pairing for their implementation. The computation cost for bilinear-pairing and elliptic curve is very high compared to the cryptographic general hash function. Therefore, all the earlier protocols suffer from the heavy computational burden and some security weaknesses as well. Therefore, bilinear-pairing-free, robust and efficient CPPA with group-key agreement protocol for VANETs is essential. This paper presents a password-based conditional privacy preserving authentication and group-key generation (PW-CPPA-GKA) protocol for VANETs. Our protocol offers group-key generation, user leaving, user join, and password change facilities. Our protocol is lightweight in terms computation and communication since it can be designed without bilinear-pairing and elliptic curve.