# Internet-of-Things and Information Fusion: Trust Perspective Survey
## 6 Internet-of-Things Architectures for Modeling Trust  
### Centralized Architectures  
Authors in [33] proposed a centralized architecture for trust evaluation in IoT. They utilized the publish-subscribe paradigm in which service providers (publishers) publish the sensor data to the broker and service consumers (subscribers) receive notifications related to their interests from the broker. In their approach, trust computing and prediction module is placed on the cloud. Authors in [61] proposed a centralized architecture for modelling their proposed trust model. In this architecture, IoT objects must register with a centralized service server and publish their services. A centralized trust management server receives feedback from these objects after every transaction. This server computes and stores the reputation and contextual trust values. The same authors enhanced their proposed work in [33] by using a clustered architecture [62] to reinforce security as well as minimize the number of stored trust values on each constrained object. It should be noted that [62] still utilized centralized servers to manage the trust.  
A centralized architecture was proposed in [63] where a centralized trust entity maintains trust levels of IoT objects and chooses the best capable object to serve a request. Authors in [64] proposed a centralized architecture for modeling trust where a central server calculates, stores, and updates trust values of the IoT objects. Service and path discovery are also achieved through a centralized database server.  
In [65], authors proposed a centralized architecture for trust management of SIoT that incorporates recommendation, reputation and knowledge trust metrics. Recommendation metric denotes the opinions of trustor-related entities to the trustee. Reputation metric is utilized to maintain the global opinions on the trustee. The knowledge metric represents the provided information by the trustee to assess its trustworthiness based on trust metrics such as cooperativeness, honesty, experience, and community of interest. To deal with the scalability issue, they have suggested to utilize  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & \multicolumn{2}{c}{**Trust Integration**} & \multicolumn{2}{c}{**Target Node**} & \multicolumn{4}{c}{**Fusion Operator/Method**} \\ \cline{2-9}  & **Selection** & **Fusion Process** & **Source** & **Aggregator** & \multicolumn{2}{c}{**Cumulative**} & **Averaging** & **Consensus** & **Others** \\ \hline
[57] & ✓ & & ✓ & & & ✓ & & & \\
[89] & ✓ & & ✓ & & ✓ & & & \\
[46] & ✓ & & ✓ & & ✓ & ✓ & & & ✓ \\
[53] & ✓ & ✓ & ✓ & & ✓ & ✓ & & & ✓ \\
[51] & ✓ & ✓ & ✓ & & ✓ & ✓ & & & ✓ \\
[49] & & ✓ & ✓ & & & & & ✓ \\
[52] & ✓ & ✓ & & & & & & ✓ \\
[60] & & ✓ & ✓ & ✓ & ✓ & & & ✓ \\
[99] & ✓ & & ✓ & ✓ & ✓ & ✓ & & ✓ \\
[21] & ✓ & & ✓ & & ✓ & & ✓ & \\
[45] & ✓ & & ✓ & & ✓ & & ✓ & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Classification of trust-based information fusion approaches.  
fog-based architecture. However, details of the architecture are not covered and many trust and social relationships metrics are overlooked in this study.  
An architecture to manage trust is proposed in [66]. The proposed system consists of distributed trust agents for producing and filtering trust parameters. These trust parameters are managed in a centralized manner. In [67], authors proposed a centralized trust management architecture that contains a supernode to serve as a centralized trust manager. The IoT system is divided into clusters, where the supernode stores the trust values of all IoT objects in a central repository.  
IoT trust (IoTrust) architecture is proposed in [20]. This architecture integrates _software defined network_ for IoT and proposes five layers namely reputation management layer, organization layer, _software defined network_ control layer, node layer, and object layer. The node and organization reputations are evaluated at a reputation management centralized repository.