# Towards Security Joint Trust and Game Theory for Maximizing Utility: Challenges and Countermeasures
## 4 Trust Model, Trust Mechanism, and Trust Framework in Networks  
The concept of trust has been widely introduced into networks. When there are multiple players in the network, trust becomes a key evaluation metric for each player's decision-making [25]. Many scholars have introduced trust and reputation into the network, and improved network utility through trust management against various malicious attacks [65; 67], improving network security. In the literature that we researched, the introduction of the concept of trust provides better performance for the network. Some researchers have evaluated key factors in the network by using trustworthiness or trust value [83; 84]. Some researchers have introduced the trust model, trust mechanism, or trust framework in the network [85; 86]. Here, we only classify and elaborate the trust model, trust mechanism, and trust framework, as shown in Table 2.  
The trust model is introduced into the wireless sensor network, by using trust evaluation to improve the security of the network [52; 58; 64; 87]. There are fixed relationships in some networks, such as social trust or social reciprocity. Modeling trust models based on these social relationships improves the data rate in D2D communications [53; 79]. It can also improve social welfare in social networks [69]. For some networks with operators or mobile users, the introduction of the trust model provides good help for users' choice [40; 49]. In military tactical network and multi-agent systems, there are often multiple players. The introduction of the trust model promotes the trust relationship between players, thereby improving mission effectiveness [34; 75]. The introduction of the trust mechanism is often to solve the problem of security and efficiency in the network [42; 43]. For example, in a P2P network, the trust mechanism can help peers make interaction decisions and prevent malicious peers [82]. Trust mechanisms can also increase the efficiency of spectrum and bandwidth sharing in the network [32; 78]. The information sharing and interaction in the network are carried out normally, and the overall efficiency of the network is improved [17]. In the fight against collusion attacks in the cloud service community, the introduction of a trust framework minimizes the number of malicious services [57]. In [15], researchers have proposed a dynamic trust framework to detect selfish and malicious nodes, and the entire network utility has been improved. Not only for the network, but the routing protocols also improve their security due to the introduction of trust [21].  
The introduction of trust provides a solution to maximizing network utility from another perspective. Different from the introduction of game theory, the introduction of trust is more targeted. Trust is introduced in networks that have trust relationships. In these networks, trust is an important metric for information interaction [73]. The introduction of the trust model mainly solved the problems of social welfare and social efficiency. The introduction of trust mechanism and trust framework solved the problem of resource sharing and malicious attacks. Therefore, the use of trust to solve problems in the network has broad research prospects.