# Sensor Network Environments: A Review of the Attacks and Trust Management Models for Securing Them
## 8 Trust Model Design Case Study: Factory 4.0 vs. Agriculture 4.0
### Trust Model Topology  
With different environments come different network topologies. The network topologies should be optimized to suit the needs of the sensors/equipment. By analyzing the typical Factory and Agric 4.0 structures shown in Table 2, two network topologies were designed to suit each case's needs.  
The Factory 4.0 network, as stated, often has more access to infrastructure, such as power and communications. This eliminates concerns regarding these limiting factors in the network. Often, the sensor and network nodes are fixed (they do not enter and leave the network frequently). An ideal network type for this would be a single (non-clustered) static heterogenous sensor network, such as the ones used in many of the IoT and CPS systems reviewed [9; 10; 11].  
Agric 4.0 consists of a wider variety of networks and sensor types. There can be both large and small area networks in the same farm, and there can be unmanned ariel vehicles (drones), autonomous machinery and livestock. Agric 4.0 poses different challenges than most studies reviewed in this paper, and may thus need a unique network and trust model structure. A structure that could work for Agric 4.0 topologies would be a clustered hierarchical network structure with distributed trust calculations that can be combined and monitored at the base station. Clusters can be thought of as their own unique network, and trust can be calculated in a different manner for each cluster, e.g., one cluster could be a cluster for the long-range monitoring of crops and soil, while another could be the internal monitoring in a greenhouse or milking parlor. Each cluster can monitor its own network, ejecting malicious nodes, and the trust data can be reported back to the base station for monitoring of the trust within the entire network. This topology would be similar to the  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Attribute** & **Factory 4.0** & **Agriculture 4.0** \\ \hline \multirow{4}{*}{Area} & Generally, a smaller area physically than & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } \\  & Agric 4.0, which can consist of larger physical & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } \\  & areas but, due to access to more infrastructure, & \\  & such as highspeed reliable comm., it is not & \\  & affected as much by physical distance & \\ \hline \multirow{4}{*}{Communications} & Use of wired and wireless protocols, such as PoE, & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } \\  & WIFI, WIFI direct, Zigbee, etc. Generally, have & \\  & access to reliable communications & \\ \hline \multirow{2}{*}{Power} & Access to power sources due to nodes’ proximity & \multirow{2}{*}{\
\begin{tabular}{} \end{tabular} } \\  & to infrastructure & \\ \hline \multirow{2}{*}{Physical access to sensors} & Usually, nodes are at infrastructure that would & \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } \\  & be indoors or fenced off, with only authorized & \\ \end{tabular}
\end{table}
Table 2: Comparison on the Factory and Agriculture 4.0 environments.  
structure seen in [3], with the exception that each cluster potentially uses a slightly different trust model. Figure 2 shows an illustration of the two proposed network structures.