## 7 Scientific Issues and Deployment Implementation Routes
### The Technical Route  
According to the general research idea, the CPS model of networked ATM system is established at first. The next step should be to determine the security risks and vulnerabilities of the networked ATM system on the basis of the model, identify the security threats faced by the networked ATM system, and study the threat model of the ATM-CPS. The Bayesian Nash equilibrium strategy is used to design the ATM-CPS game model, and the blockchain technology is used to realize the trusted model so as to build the architecture of the ATM-CPS information security assurance. The specific research technical route and measures are shown in Figure 13. According to the decomposition of the research content in this paper, the design of the technical route is based on the research of the content in each stage. The specific steps are as follows.  
1. ATM-CPS model. The establishment of the networked ATM-CPS model is based on the study of the business information data flow of the ATM and the composition of the ATM, including three steps: * Determine the dynamic weighting network of the ATM system; * Establish fine granularity network model of the ATM system; * Establish the refined CPS model of the ATM system.
2. ATM-CPS threat model. Aimed at the complex composition and heterogeneous structure of the networked ATM system, the network traffic super fusion probe technology is used to conduct deep packet analysis and flow analysis for the traffic of different communication protocols and interfaces so as to realize the comprehensive and effective detection of various security threats faced by the networked ATM system. Then, it is found that the purpose of discovering system security risks and mining system vulnerabilities is achieved, the identification method of information security risks of ATM system is studied, and the information security threat model of ATM is established. The specific implementation steps are as follows:  
Figure 13: Technical route and measures of the research.  
* Carry out quantitative analysis on the impact of security threats on the core performance of the ATM system;
* Design the quantitative expression method and reference frame of the ATM system security characteristics;
* Establish the influencing factors and system model of the ATM system security measurement.
* ATM-CPS game model.  
The four aspects of ATM-CPS security situational awareness capability construction, security indicator extraction, situational prediction, and situational visualization are used to strengthen the situational awareness capability of ATM, thus laying the foundation for the establishment of ATM-CPS game model based on Bayesian Nash equilibrium strategy. The specific steps include:  
* Study the information security situation assessment method of the ATM system;
* Study the information security situation prediction method of the ATM system;
* Establish Bayesian Nash equilibrium strategy.  
Information security assurance architecture of the networked ATM system.  
On the basis of the security hidden danger and system vulnerability mining of the networked ATM, the security threats are clarified, and the information security model of the ATM-CPS is established. In addition, from the perspective of the relationship among the elements of ATM infrastructure from the top level, we design the architecture of ATM information security assurance system on the basis of blockchain trust model. The specific steps include:  
* Study the point-to-point network design of the business application of the networked ATM system;
* Establish the blockchain-based trust model of networked ATM system;
* Design the information security assurance architecture on the basis of the trusted model;
* Complete the design of information security assurance framework of the networked ATM system, including core functions, constituent elements, and logical associations.