## 6 Networked ATM-CPS Security Assurance Architecture
### The Method of ATM-CPS Information Security Assurance Based on Blockchain Trusted Model
However, by introducing the certificateless digital signature system, multiple KGCs can generate part of the user's private key in the form of ring signature, which not only solves the problem of key escrow but also reduces the pressure of a single KGC. (b) Blockchain edge layer. Blockchain edge layer is responsible for collecting data information of ATM system and submitting it to blockchain network layer. By using digital signature technology, the obtained information is written into a new block to complete the successful chaining of information. The specific access process is shown in Figure 10.  
According to the process shown in Figure 10, the specific steps are as follows. Step 1: ATM system node \(B\) reports information to edge node \(A\), uses its own private key to sign the collected information, and uses the public key of edge node \(A\) to encrypt the information;  
Step 2: After receiving the information, edge node \(A\) will decrypt and verify the signature. After the information is approved, edge node \(A\) will sign all the obtained information and submit it to the block node/\(KGC_{i}\);  
Step 3: Block node/\(KGC_{i}\) writes the information submitted by edge node \(A\) into the new block and broadcasts the information after it is signed with the ring private key \(ks\);  
On the basis of the trustable model established by the blockchain, this paper proposes a networked ATM-CPS information security assurance architecture based on the trustable model, as shown in Figure 11. The networked ATM-CPS has many cooperative subject resources, wide information sources, large data volume, and long business chain, realizing cross regional, multi-agent, and full process space-air-ground integration and multi-dimensional sharing and cooperation. Therefore, taking advantage of the characteristics of the distributed data records of the blockchain, such as certificate storage, traceability, sharing, trust, and cooperation and combining them with the basic theory and key technology of information security assurance oriented to the networked ATM system, a systematic space-air-ground integration and all-round networked ATM system information security assurance architecture is formed. This structure supports and accommodates the information security assurance technologies of ATM system, such as vulnerability mining, intrusion prevention, situation awareness, and attack defense. The example scenario. Suppose there is a flight Flight(X) from Beijing to Shanghai, which needs to pass through Tianjin, Xuzhou, Suzhou, and other places on the way. The following will consider flight plan management as an example to illustrate the application of the security architecture designed in this paper from the three stages of the flight. Before the flight: Pre-made flight plan. Flight(X) needs to formulate the flight plan and corresponding access strategies of this flight and then submit them to the information broadcasting layer. The broadcasting layer packages the information collected over a period and sends it to the blockchain terminal layer (here, the blockchain terminal layer acts as a flight plan approver). The terminal layer determines whether to approve the flight plan and provides feedback about the flight on the basis of the collection of external information (such as weather information, ground conditions, and traffic flow at the destination airport). Figure 11: Information security assurance architecture of networked ATM system based on trustworthy model. If the plan is approved, the blockchain terminal layer will record and store once to complete the generation of new blocks. During the flight: Modify the flight plan on the basis of external information. The blockchain terminal layer continues to collect updated external information. In the event of severe weather or changes in current airspace flow, the flight route needs to be changed for safety reasons, and the blockchain terminal layer will modify the flight plan and return it to the crew.