# Towards Security Joint Trust and Game Theory for Maximizing Utility: Challenges and Countermeasures
## 2 Relate Summarized Works  
In this section, we briefly describe our research work from three aspects: The application of game theory, the application of trust, and the application of joint game theory and trust; and give some examples in the literature. Through the investigation of literature, we have concluded that most researchers use the following types of games: Dynamic game [32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45], static game [46], non-cooperative game [47; 48; 49; 50; 51], cooperative game [52; 53; 54; 55; 56; 57; 58; 59], security game [60; 61; 62; 63; 64], and trust game [65; 66; 67; 68; 69]. Researchers using the dynamic game have established some mechanisms or solutions for application scenarios, solving the issues of maximizing utility in the networks/systems. The dynamic game also has some applications in solving problems related to network security [35], gaining a higher network lifetime in wireless sensor network, and obtaining higher secure caching ratio of heterogeneous networks [38; 42], such as improving the bandwidth utilization, network throughput, and other performance [32; 34; 36]. In some application scenarios, the main purpose of the game is to make an optimal pricing strategy to achieve higher utility of the system [39; 40]. In some application scenarios, players choose to cooperate and ultimately achieve a win-win situation. In device-to-device (D2D) communication, cooperative game theory can promote effective cooperation between devices and improve overall performance [53; 56]. Players in non-cooperative games are in a competitive relationship and are very common in many applications. In mobile cloud computing, a non-cooperative game model is established based on the competition behavior of multiple clients to maximize mobile terminal energy efficiency [50]. The key factor in the security game and the trust game is trust [66]. In some cases, only when the players trust each other can they get the best results. The purpose of the security game is to improve the security of the system and promote information sharing [60; 61; 62; 63; 64]. In addition to the explicit type of game model, researchers have established some game models based on different application scenarios [70; 71; 72; 73; 74]. Most of these game models are established with the following objectives as the ultimate goal: To establish trust relationships and increase the credibility of data, to defend against malicious attacks in the network, to help the system by choosing a better strategy, and to maximize network utility by achieving these goals [75; 76; 77; 78; 79; 80; 81]. From the perspective of game theory, we can get the above types. We can also analyze and summarize the research literature from the perspective of trust and application scenarios. In this literature, researchers use trust relationships, trustworthiness, and other factors for decision-making. Based on trust, the researchers proposed some trust models [34; 40; 49; 52; 53; 58; 59; 64; 69; 75; 79], trust mechanisms [32; 42; 78; 82], and trust frameworks [57]. They provide a better selection scheme for players in the network/system through trust evaluation. In mobile social networks, researchers have used trust evaluation to propose a reliable secure caching scheme, which saves cache time and improves secure caching ratio [49; 51]. In terms of network security, researchers have established intrusion detection systems through games and trust management to improve the security network [47]. The concept of trust and game has been introduced into various fields. By introducing a dynamic game model, some researchers use trust relationships to build a game model, improving the security of the networks. They establish a strategic trust mechanism in the internet of things and cyber-physical systems and use game theory to capture the adversarial and strategic nature of cyber-physical systems security [37; 43].