## 3 System Model
### Threat Model and Assumptions
#### 4.1.2 Authentication and Encrypted Transmission  
The previous section introduced the algorithm related to node identification, by which this identification and the implicit information contained can be used to achieve security and confidentiality when two nodes transmit information in an insecure channel. In order to simplify the process of node identification and encrypted communication, the following two types of network communication between nodes are classified according to the type of information transmitted between them, facilitating the selection of the appropriate type in the appropriate case. * Public message transmission: Transferring information that can be made public in the network between two nodes, verifying each other's nodes' identities, signing the authenticity of messages and preventing them from being tampered with, but not from being eavesdropped. Generally only one round of interaction takes place, so no transmission channel is established. * Confidential message transmission: Encrypted messages are delivered between two nodes, generally transmitting user data with large data volumes, so virtual encrypted channels are established to ensure the confidentiality of messages based on two-way identity authentication. As shown in Figure 7, the interaction process of public messaging is demonstrated. The initiator is Node A and the receiver is Node B. The first interaction completes the authentication process. The second interaction completes a two-way pass of the public message. The random number mechanism prevents replay attacks and the message signature ensures that the message is tamper-proof. The detailed flow of the interaction process is as follows. 1. Node A first initiates a connection to Node B, sending its public key and \(NodeID\). 2. Node B verifies that the \(NodeID\) and the public key sent by Node A satisfy the correspondence, as well as calculating whether \(Diff_{n}\) satisfies the requirements in the network. Generate the random number \(None1\). Sign the public key of node B and \(None1\) using the private key and send the data and signature to node A. 3. Node A verifies that the \(NodeID\) and the public key sent by Node B satisfy the correspondence. Verify that the signature is correct using the public key of node B. Generate a random number _Nonce2_. Sign _Nonce1_, _Nonce2_, the data to be passed using the private key, and send all data and the signature to node B. 4. Node B uses the public key of node A to verify that the signature of the message sent by node A is correct, compares the _Nonce1_ sent with the random number _Nonce1_ generated by node B. The data and _Nonce2_ to be sent are signed with the public key of node B, and the data and signature are sent to node A. 5. Node A uses the public key of node B to verify that the signature of the message sent by node B is correct, and compares whether the _Nonce2_ sent is whether the random number _Nonce1_ generated by Node A. As shown in Figure 8, the interaction process of confidential messaging is demonstrated. The initiator is Node A and the receiver is Node B. The first interaction process completes the authentication and the generation and interaction of a new pair of public and private keys, and the second interaction process completes the key transfer for the symmetric encryption needed to establish the message channel, and then the encrypted channel is established, and Node A and Node B can communicate securely at that time. The detailed flow of the interaction process is as follows. 1. Node A first initiates a connection to Node B, sending its public key and _NodeID_. 2. Node B verifies that the _NodeID_ and public key sent by node A satisfy the correspondence, as well as calculates whether \(Diff_{n}\) satisfies the requirements in the network. Generate a new elliptic curve private key \(dB\), calculate \(HB=dB*G\) based on the elliptic curve shared parameter base point \(G\), sign the public key of node B and \(HB\) using the private key, and send the data with the signature result to node A. 3.