# Towards Security Joint Trust and Game Theory for Maximizing Utility: Challenges and Countermeasures
## 3 Game Theory in Networks  
Decision-making is a behavior that is prevalent in politics, economy, technology, and daily life. It can achieve specific objectives and make decisions on future behaviors by analyzing, calculating, and judging the achievement of the target. In the literature that we have researched, researchers have introduced game theory into the network to improve network utility in various aspects. In this section, we analyze and summarize the types of game cited in this literature. We divide the types of game into seven categories, as shown in Table 1.  
By introducing a dynamic game, the researchers proposed solutions for several aspects of the network/system. In terms of strategy selection, they proposed introducing the game theory into the peer-to-peer (P2P) energy trading problem in industrial Internet of things (IIoT), proposing an optimal pricing strategy using Stackelberg game for credit-based loans in [39]. In the vehicular networks, the optimal strategies of energy entities are analyzed by using the game theory [40]. In the process of strategy selection, in order to jointly improve the network utility from multiple angles, we are often looking for equilibrium. To improve the network utility, it is necessary to introduce dynamic game into the key factors in the network and calculate the equilibrium between them. In a military tactical network, in resource-restricted tactical environment, the equilibrium between group trust and system lifetime is achieved, and mission effectiveness is improved [34]. Based on game theory, a dynamic behavior monitoring scheme for evidences collection in wireless sensor networks is proposed. Equilibrium between network security and energy conservation can be achieved [38]. Game theory as a strategy selection scheme has also been introduced into the intrusion response systems [29]. The game theory is used to investigate the interactions among edge computing-enabled small cell base stations (ECSBSs) and mobile users, and the Nash equilibrium is calculated to jointly maximize the utilities of ECSBSs and mobile users [42]. To improve network performance, we need to use game theory to capture the interaction between devices and the cloud and calculate Nash equilibrium [43]. In the context of big data, game theory is used to analyze the profits between doctors and patients, and thus improve the total benefit of the medical system [44]. In some networks/systems, the introduction of dynamic game promotes network security and resource sharing efficiency. In cognitive multi-hop cellular networks, a new cognitive radio bandwidth-sharing scheme is proposed based on game theory, and the bandwidth utilization is improved [32]. In the spectrum sharing scheme, using game theory to quantitatively analyze the interaction between the primary users and secondary users, it can promote spectrum sharing in a tiered manner [36]. Game theory is introduced into the network to perform modeling analysis to prevent malicious node attacks or leaky deception in the network and improve the secrecy rate in the network, thereby improving the security of the network [33; 35; 37; 45]. In device-to-device communication, the introduction of game theory has increased the utility of operators [31]. In the smart grid in a large population regime, the introduction of game theory has maximized the profit of providers and users [18]. Contrary to dynamic game, static game is less used. In the literature [46], static game is introduced into cloud radio access network (C-RAN). Researchers analyzed whether the operators would like to collaborate with each other by applying game theory and improve the utility between operators. In [19], the problem of efficiently coordinating price-responsive appliances operating in the electricity market is tackled within a game theoretical framework. According to whether the players cooperate, the game is divided into cooperative game and non-cooperative game. The common goal of both games can maximize network utility and improve network security.