## 4 Proposed Protocol Procedure
### Authentication and Key-Exchange Phase
#### 4.2.1 Step 2  
In this step, The node's encrypted message is received by the server, which includes parameters \(\mathrm{S_{1}}\), \(\mathrm{S_{3}}\), and K. After receiving the message, the server must first calculate the \(\mathrm{\Delta T}\ (\mathrm{1T_{2}}-\mathrm{T_{1}}\ )\) time gap upon message arrival to assess message freshness and to avoid sending duplicate messages and to prevent replay attacks (T1 refers to the time of sending the message and T2 refers to the time of receiving the message). Upon satisfaction with the message's freshness, the server needs the symmetric key to decrypt the message. To obtain this key, the server calculates the N\({}_{\text{i}}\) parameter by multiplying the scalar of its private key with the received value K. Two significant considerations arise in this context. First, in line with the ECDH protocol, the attacker's capacity to calculate N\({}_{\text{i}}\), even with K, is restricted. Second, as dictated by the ECDLP problem, the value of N\({}_{\text{i}}\) is only accessible through the scalar multiplication of the Server's private key with K. Using the advantages of this theory helps the protocol to implement a better-quality authentication mechanism, and the presented protocol can provide significant efficiency against all kinds of network attacks. (1) \(\text{N}_{\text{i}}{}^{\prime}=\text{PV}_{\text{S}\text{E}\text{V}\text{E} \text{V}}\text{.K}\)  
Note: The server needs to have the value of K to generate the value of Ni and reach the X dimension of Ni. The value of K is sent by the node, based on the ECDH described in the introduction section; network attackers cannot calculate the value of Ni by having the value of K.  
After obtaining the encryption key through the accurate calculation of N\({}_{\text{i}}{}^{\prime}\), the process of authentication and validation of parameter accuracy initiates. In pursuit of this goal, the server computes the parameters A\({}^{\prime}\), S\({}_{2}\), and S\({}_{3}\) using the provided information. (2) \(\text{A}{}^{\prime}=\text{H}(\text{S}_{1}\mid\text{N}_{\text{i}}{}^{\prime} \mid\mid\text{AC}_{\text{i}})\)  
(3) \(\text{S}^{\prime}_{2}=\text{H}(\text{S}_{1}\mid\text{N}_{\text{i}}{}^{\prime} \mid\text{(x)}\mid\text{K}\mid\text{A}{}^{\prime})\)  
(4) \(\text{S}^{\prime}_{3}=\text{H}(\text{A}{}^{\prime}\mid\text{S}^{\prime}_{2} \mid\text{AC}_{\text{i}})\)  
The server, in order to produce the S\({}_{3}\) value, is required to initially compute A\({}^{\prime}\) and S\({}_{2}\). For the calculation of A\({}^{\prime}\), the server utilizes the encrypted form of the parameter S1 sent by the node, the previously generated AC\({}_{\text{i}}\) parameter for the node, and the N\({}_{\text{i}}\) parameter obtained in the server's prior calculations. As can be seen, if entities other than the server that owns the private key attempt to generate N\({}_{\text{i}}\), they will not be able to reach the symmetric encryption key because the Ni can be recalculated only with the server private key based on ECDLP. Also, parameter S1 is not accessible because it is encrypted by the dimension (x) of parameter N\({}_{\text{i}}\). In addition, in the process of calculating A\({}^{\prime}\), the server-generated certificate (AC\({}_{\text{i}}\)) is needed for the node, which is a private parameter between the server and the node. Therefore, the hostile or unauthorized person needs access to the private parameters used in the production of A, which prevents the creation of calculation conditions and the access of the hostiles to the value of A\({}^{\prime}\). Upon computing the parameters A\({}^{\prime}\) and S\({}^{\prime}_{2}\), the server generates the parameter S\({}^{\prime}_{3}\) to verify both the accuracy of the transmitted information and the authenticity of the message sender. The server verifies the accuracy of the value information by comparing the value of S\({}^{\prime}_{3}\) with its ownvalue, simultaneously ensuring the authenticity of the sender (node).