*3.1. System Model*

The system model is comprised of three things, namely the Trusted Authority (TA), RSU, and Vehicles. The depiction of the system model is shown in Figure 2. The Trusted

Authority (or certification authority or Government Authority) is assumed to be honest and will not take part in compromising vehicle location [62,63]. The vehicle must be registered with the TA before joining the ad hoc network. The TA provides a pseudonym pool to vehicles to be used for a number of days. The pseudonym is used for anonymous broadcast of beacon messages. On the expiry of its pseudonym pool, the vehicle can request another pseudonym pool from the TA. We assume that the vehicle has been registered with TA and is assigned a pseudonym pool. An RSU is a roadside infrastructure fixed on the road to increase the communication range of vehicles. It is a semi-honest entity in the system model, and it may or may not compromise the privacy of a vehicle. RSUs also play a role in the dissemination of data to other entities of the system model. We also assume that the authentication process is performed by each vehicle. The vehicle contains an OBU that is used for communication with other OBUs and infrastructure in the network. OBU records communication events of vehicles. The vehicle has a tamper-proof device that stores the key materials securely, such as anonymous identities and records of all communication events [64]. The vehicle is also equipped with GPS for precise location updates.

**Figure 2.** Basic system model.
