## 4 Proposed Protocol Procedure
### Authentication and Key-Exchange Phase  
The authentication and key-exchange phase comprises three steps, wherein the communicating parties authenticate each other using various parameters within the proposed protocol. During this phase, specifically in the three-stage process of authentication and key agreement, a mechanism is employed. In this mechanism, the node and the server use a dynamic symmetric encryption key to secure the exchanged data. Additionally, throughout this phase, mutual authentication takes place with distinct parameters. Finally, in the last step, the communicating parties generate a secure session key based on private and verified parameters. The node acts as the starting point for communication with the server. Step 1. To initiate the protocol process, the node starts by selecting random numbers, ai and bi. In the protocol process, private parameters are used to generate different values. The reason for using private parameters is to make it impossible to calculate the values generated by network attackers and to maintain the security of the protocol. There are various attacks, such as reply, impersonation, and other network attacks, that can be prevented by using the features of private parameters. The utilization of private parameters requires security issues to be considered in the protocol process. In the process of the presented protocol,  
Figure 2: Registration phase. we have taken advantage of the features of the server and node's private key, which we have prevented from being used directly to maintain the security of this sensitive private parameter. To protect the private keys of each entity in the provided protocol process, we have combined the keys with random numbers and used a root generated from the private keys. This operation prevents private keys from being used directly. Implementing the private key combination mechanism with random numbers in the protocol process enables us to furnish the security features mentioned for the presented protocol. Subsequently, the values S1, K, and Ni are produced. 1. \(\mathrm{S_{1}}=(\mathrm{PV}_{\mathrm{NODE}}\ ^{*}\mathrm{a_{i}})+\mathrm{b_{i}}\)
2. \(\mathrm{K}=\mathrm{b_{i}}.\mathrm{P}\)
3. \(\mathrm{N_{i}}=\mathrm{b_{i}}.\mathrm{PU}_{\mathrm{SERVER}}\)  
The generation of \(\mathrm{S_{1}}\), \(\mathrm{K}\), and \(\mathrm{N_{i}}\) involves scalar multiplication of the base point (P) and the server public key with the random number \(\mathrm{b_{i}}\). With a two-fold purpose, these parameters handle dynamic symmetric key selection and authenticate the node to the server. The security of the dynamic symmetric session-key generation mechanism is implemented by taking advantage of the features of the ECDH. Upon generating the \(\mathrm{N_{i}}\) value, the node picks the x-dimensional value of the \(\mathrm{N_{i}}\) point as the symmetric encryption key. According to the process of calculating the value of Ni, it is completely understandable that the existence of random numbers (bi) in this process means that every time this parameter is produced, the value produced is completely different from before. The distinctiveness and uniqueness of the symmetric key eliminates the potential vulnerabilities that arise from using static keys in the realm of symmetric cryptography. Upon the selection of the symmetric encryption key, the node creates parameters \(\mathrm{A}\), \(\mathrm{S_{2}}\), and \(\mathrm{S_{3}}\). During this phase of the protocol procedure, the aim of generating these parameters is to enforce the authentication of both the node and the server. The server evaluates the node's identity by re-calculating the parameters. 1. \(\mathrm{A}=\mathrm{H}(\mathrm{S1}\ |\ \mathrm{Ni}\ |\ \mathrm{ACi})\)
2. \(\mathrm{S2}=\mathrm{H}(\mathrm{S1}\ |\ \mathrm{Ni}(\mathrm{x})\ |\ \mathrm{K}\ |\ \mathrm{A})\)
3.