# Towards Security Joint Trust and Game Theory for Maximizing Utility: Challenges and Countermeasures
## 1 Introduction
In this literature, the author introduces game models into network/system to achieve specific goals. These goals can be roughly divided into the following categories: (1) Improve the network security. The improvements of network security include data protection, prevention attacks, and eliminating of malicious nodes. Game theory is used to establish an attack defense system to prevent attacks [4]. Game and trust are applied to the network at the same time, and related mechanisms are established to eliminate malicious nodes to protect the security of data [5]. (2) Maximizing utility, such as improving social efficiency and maximizing the profits of players. In the power network, the profits of suppliers and customers are often improved through games. In some networks, players' profits are maximized through resource allocation [6]. It is also used to establish a routing mechanism or incentive to select strategies through games and improve the performance of the network [7; 8; 9]. Especially in the process of data transmission, the selection of sensors or nodes has a good application prospect [10; 11]. In the network, not all players to which game theory is applied are perfectly rational. Thus, evolutionary game theory has been proposed. In terms of methodology, it differs from game theory's emphasis on static equilibrium, which emphasizes a dynamic equilibrium [12]. In the application of games, in order to achieve equilibrium, players usually face the choice of competition or cooperation. Similarly, in systems with agents, competitiveness strongly increases cooperation [13]. Cooperation in the network is based on trust. As the application scenarios of games and trust, networks can be divided into various forms. Typical networks are distributed networks, centralized networks, and social networks. In a distributed network, the number of nodes is large, the structure is complex, and the connections are diverse. Centralized networks are prone to network congestion. The relationships of players in social networks are complex and dynamic. All three networks can be called complex networks. The study of complex network models has a certain guiding role in dealing with the problems existing in real networks. The structure of a system and the structure of a network are closely related to its functions. Each of the three networks covered in this paper has its own topology. The change of the topology structure affects the utility and security in the network. The relationship between trust, game theory, and networks is shown in Figure 1.  
Social network refers to a relatively stable relationship system formed by the interaction between individual members of society. Social networks represent a variety of social relationships. Trust and trustworthiness are very important in social and human systems, especially when considering human and economic decisions. Therefore, the design of the game model in these studies is based on the trust relationship of the players in application scenarios [14; 15; 16; 17; 18; 19]. Distributed networks are interconnected by nodes at multiple terminal distributed in different locations. Reliability is a key characteristic of distributed networks and a key factor in ensuring network availability [20]. In distributed networks, networks are often subject to malicious attacks. These attacks can disrupt the transmission link of the network, which in turn disrupts network availability. How to choose a reliable node for transmission, and how to isolate malicious nodes out from the network quickly and accurately, are crucial [21; 22; 23]. To find the optimal choice in distributed network, game theory is an effective solution [24; 25; 26]. Combining a trust relationship between nodes and games can solve problems such as path selection in distributed networks. A centralized network is a large central system. In a centralized network, all data are stored in a central system and the terminal is the client [27].