# A Framework for Constructing a Secure Domain of Sensor Nodes
## 5 Results and Discussion
### Security Evaluation  
A comprehensive security solution for the critical application of IoT should include three basic features: preventative, detective, and reactive measures [4]. Our framework for constructing a secure  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Packet** & **Packet** & **Direction** & **Required** & **Number of** & **Number of** & **Number of** \\
**Name** & **Length (B)** & & **Number of** & **Bytes in** & **Xbee** & **Bytes in** \\  & & & **Packages** & **Packets (B)** & **Frames** & **Xbee** \\ \hline status\_refresh\_req & 18 & M \(\rightarrow\) R & 1 & 18 & 1 & 34 \\ status\_refresh\_ans & 22 & R \(\rightarrow\) M & 1 & 22 & 1 & 38 \\ \hline  & \multicolumn{2}{c}{Total} & 2 & 40 & 2 & 72 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Transmission requirements for the procedure for refresh the status of one node.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Packet** & **Packet** & **Direction** & **Required** & **Number of** & **Number of** & **Number of** \\
**Name** & **Length (B)** & & **Packages** & **Packets (B)** & **Frames** & **Xbee** \\ \hline status\_confirm\_req & 38 & R \(\rightarrow\) M & 1 & 38 & 1 & 54 \\ status\_confirm\_ans & 34 & M \(\rightarrow\) R & 1 & 34 & 1 & 50 \\ \hline  & \multicolumn{2}{c}{Total} & 2 & 72 & 2 & 104 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Transmission requirements for the procedure confirming the status of one node.  
domain of sensor nodes mainly focused on the first type of measures. This indicates that it is aimed at prevention or at the very least, at making some common attacks much more difficult. However, this does not mean that the application of detective and reactive measures has not been foreseen in the proposed solution.  
We propose some diagnostic procedures built upon system level diagnosis where the sensor nodes of the domain are capable of performing assigned tests among themselves. After performing all mutual tests between nodes, based on the test results obtained, the nodes that do not work correctly can be identified (with certain restrictions). By using the appropriately designated structure of mutual node testing, the domain's ability to detect or locate faulty or (misbehaving) nodes can be obtained.  
After identifying the misbehaving nodes, a domain reconfiguration is carried out, which, in the case of failure/malfunction of the nodes that perform the Replica role (R nodes), excludes them from the domain. If a malfunctioning M or G node is identified, the procedure for selecting a new node to perform these roles is started. All diagnostic and reconfiguration procedures are protected cryptographically using the NDK (different symmetric keys for messages encryption ) and are limited to authenticated nodes only.  
The main difficulty in securing wireless IoT networks is the fact that sensor nodes could be unattended. This leads to the threads that are not viable in another type of network. Let us consider common real-life threads and attacks for wireless sensor networks, such as malicious sensor node injection (node replication attack), sensor impersonation (imitation), attacks on the information in transit, denial-of-service attacks (DOS attacks), and routing attacks [4].