## 3 Background
### Trust Management in IoV
#### 3.1.6 Trust Management Approaches  
Entity-based approaches, data-based approaches, and integrated approaches are the three types of trust management approaches. The trust concept is related with network nodes in an entity-based approach. These methods are used to assess how trustworthy the nodes in a network are that send and receive data. Malicious nodes can subsequently be excluded from the network or isolated based on the evaluation of their trust ratings. Social trust interactions are inherited by certain existing entity-based techniques in the literature. These methods primarily consider measures that are based on a person's reputation. As a result, the trust formula used to generate the trustee node's trust value is mostly dependent on previous knowledge-related metrics as well as traded recommendations among various entities. Other studies look at comprehensive trust, considering not only reputation-based indicators but also the similarity aspect. In data-based systems, the concept of trust is closely associated with the integrity of the generated message, hence necessitating the assurance of data authenticity in these solutions. Utility refers to a specific helpful act or the worth of the created event compared to other actions in the same context, and it is an essential factor in determining data content worthiness. The proximity time, the type of incident that occurred, and the role of the vehicular node are some of the major trust elements considered in data utility assessments. Information-oriented methods and event-oriented methods are two types of data-driven approaches. Similarity is a term that describes how the contents of shared data are similar in terms of time and proximity criteria, and it is used to determine the value of data trust. Similarity aids in reducing the amount of data disseminated, ensuring that only meaningful information is broadcast. The primary principle of the combined trust management technique relies on entity and data-sharing trustworthiness. This module is more efficient when it comes to trust computation. The assessment of data trust value is aided by entity trustworthiness.  
An example was provided to address the issue of injecting inaccurate information into safety-related events in VANETs, in which a similarity-based solution was proposed [35]. The calculation of a similarity rating is based on periodic beacons that contain position and speed information. An Echo procedure was also used to acquire a trust rating and to validate the reports by observing the vehicle's normal and expected behavior in relation to the reported occurrence. In a VANET presented in [36], a multidimensional trust system was created for the agents. In order to require further feedback from trustworthy nodes, the system's trust values must be maintained. When determining trustworthiness, authors take into account variables including experience, majority opinion, and priority criteria. These schemes classify nodes as having an authority role, an expert role, a seniority role, or an ordinary role. It is also worth noting that the experience factor is calculated as a result of the number of encounters. To deal with behavioral changes, the forgetting factor is introduced. Each node communicates its trustworthiness to other entities through trust messages sent to an authentic infrastructure, which later becomes a component of the reputation management center, where node trust is collected [37]. Authentic infrastructure filters trust communications based on statistical regularity, and each node then has access to updated trust data from the reputation center. Historical trust can be determined with the use of authentic center recommendations [38]. Platoon head vehicles are ranked using the reputation criteria. The system model includes servers that are used to assess the trust of vehicles, and reputation values are calculated using feedback from user vehicles. The use of iterative filtering eliminates any malicious user vehicle feedback. The server node then suggests a safe platoon leader vehicle.