# Towards Security Joint Trust and Game Theory for Maximizing Utility: Challenges and Countermeasures
## 5 Analysis and Comparison Based on Application Scenarios
### Application Scenarios  
A centralized network facilitates data management. In a centralized network, data are processed centrally and all information is managed by a database. The terminal is only used for input and output. In our research literature, researchers combine game theory and trust to optimize networks or systems, including wireless network, cyber-physical systems, multi-agent system, and other application scenarios. In a centralized network, utility is typically evaluated by using the following metrics: Secure caching ratio and average saved time [42; 49; 51]; service cost, service quality, or transmission overhead [54; 70; 74];  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Trust Model** & **Trust Mechanism** & **Trust Framework** \\ \hline [PERSON] et al. [52] & & \\ [PERSON] et al. [53] & & \\ [PERSON] et al. [34] & & \\ [PERSON] et al. [75] & [PERSON] et al. [82] & \\ [PERSON] et al. [69] & [PERSON] [32] & \\ [PERSON] et al. [49] & [PERSON] et al. [78] & [PERSON] et al. [57] \\ [PERSON] et al. [79] & [PERSON] et al. [42] & [PERSON] et al. [15] \\ [PERSON] et al. [40] & [PERSON] et al. [43] & \\ [PERSON] et al. [58] & & \\ [PERSON] and [PERSON] [64] & & \\ [PERSON] et al. [59] & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Classification of trust applications.  
social welfare [68; 83]; network throughput or total amount of data transferred [32; 78]; energy efficiency or operation efficiency [46; 50]; or detecting the network's against attack ability and defense costs through simulation experiments [37; 43; 81].  
Distributed networks have high reliability. All nodes are randomly distributed in the network and there is no management of the central node. There are many path selections during information transmission, and resource sharing is easy, but it is vulnerable to malicious nodes. In a distributed network, network performance is often evaluated through security and efficiency [52; 55; 82; 84], or metrics based on energy efficiency, trustworthiness of data transmission, and cost-efficiency [38; 39; 47; 58; 59].  
In social networks, each member of the society has formed a relatively stable relationship system due to interaction. Social networks often represent a variety of social relationships. The social network can be either an individual or an organization. In social networks, network throughput and data storage rate are often used as evaluation metrics [15; 57; 79; 85]; or energy efficiency, information transmission rate, and social welfare are used as metrics [48; 53; 69]. There are also some social networks that protect players' privacy through trust evaluation [16].  
In summary, different networks have different metrics. Centralized networks are prone to network congestion, so their metrics are often related to transmission efficiency or time overhead. Distributed networks are vulnerable to various attacks, so their metrics are often related to security and accuracy. Social networks are most concerned with social efficiency, therefore often assessed on the basis of throughput and social welfare. The introduction of game theory and trust provides a good solution for improving these metrics in the network.  
Figure 2: Some performance metrics related to utility.