# Trustworthiness of Situational Awareness: Significance and Quantification
## 4 Quantifying Trustworthiness of SA
### Model for Quantifying the Trustworthiness of COP
The trustworthiness of a source \(S_{i}\) can be given as  
\[\mathcal{T}_{S_{i}}=f\big{(}C_{S_{i}},I_{S_{i}},A_{S_{i}},\mathcal{A}_{S_{i}}, \mathcal{N}_{S_{i}},P_{S_{i}},Q_{S_{i}},U_{S_{i}}\big{)}, \tag{1}\]  
where \(\mathcal{T}_{S_{i}}\), \(C_{S_{i}}\), \(I_{S_{i}}\), \(A_{S_{i}}\), \(A_{S_{i}}\), \(\mathcal{N}_{S_{i}}\), \(P_{S_{i}}\), \(Q_{S_{i}}\), and \(U_{S_{i}}\) denote the trustworthiness, confidentiality, integrity, authenticity, availability, non-reputability, precision, quality, and usability, respectively, of a source \(S_{i}\). As discussed in Section 1, the source \(S_{i}\) could be any of the sources providing SA including HUMINT, MASINT, MINT, OSINT, SIGINT, and GEOINT. The function \(f(\cdot)\) in Equation (1) indicates that the trustworthiness \(\mathcal{T}_{S_{i}}\) is a function of the confidentiality, integrity, authenticity, availability, non-reputability, precision, quality, and usability of a source \(S_{i}\). This function \(f(\cdot)\) can be a simple addition or weighted addition or some other combination of the metrics of source \(S_{i}\) for confidentiality, integrity, authenticity, availability, non-reputability, precision, quality, and usability. Delay or latency of information obtained from a source also impacts its trustworthiness. A lower usability score can be assigned to a source with large delay/latency, as SA information is often time-sensitive. We note that Equation (1) captures the situation in case a HUMINT source is compromised or less trustworthy, where a lower integrity score can be assigned to that source. Nevertheless, the detection of a compromised and less trustworthy HUMINT source requires HUMINT, MASINT, OSINT, SIGINT and other intelligence gathering means. To communicate the SA information from a source to the COP builder, there can be many nodes (or devices), such as relay nodes, gateway nodes, and data fusion nodes, along the way. We can denote the set of these nodes as \(D=\{d_{1},d_{2},d_{3},\ldots,d_{K}\}\), where \(K\) denotes the total number of such nodes. Similarly, there are links that connect sources to different nodes/devices and ultimately the COP builder. We can denote the set of these links as \(L=\{l_{1},l_{2},l_{3},\ldots,l_{M}\}\), where \(M\) denotes the total number of such links. The trustworthiness of SA information at the COP builder provided by the source \(S_{i}\) can be determined as  
\[\mathcal{T}_{COP}^{S_{i}}=\mathcal{T}_{S_{i}}\cdot\prod_{j=1}^{K}\mathcal{T}_{ d_{j}}\prod_{m=1}^{M}\mathcal{T}_{l_{m}}, \tag{2}\]  
where \(\mathcal{T}_{d_{j}}\), \(j\in\{1,2,3,\ldots,K\}\) and \(\mathcal{T}_{l_{m}}\), \(m\in\{1,2,3,\ldots,M\}\) represent the trustworthiness of nodes/devices \(d_{j}\) and the links \(l_{m}\), respectively, along the way from information source \(S_{i}\) to the COP builder. The trustworthiness of a node \(d_{j}\) can be calculated as  
\[\mathcal{T}_{d_{j}}=f\Big{(}C_{d_{j}},I_{d_{j}},\mathbb{A}_{d_{j}},\mathcal{A} _{d_{j}}\Big{)}, \tag{3}\]  
where \(\mathcal{T}_{d_{j}}\), \(C_{d_{j}}\), \(I_{d_{j}}\), \(\mathbb{A}_{d_{j}}\), and \(\mathcal{A}_{d_{j}}\) denote the trustworthiness, confidentiality, integrity, authenticity, and availability of a node \(d_{j}\). The function \(f(\cdot)\) in Equation (3) is similar to the one in Equation (1). The trustworthiness of a link \(l_{m}\) can be calculated as  
\[\mathcal{T}_{l_{m}}=f(C_{l_{m}},I_{l_{m}},\mathcal{A}_{l_{m}},Q_{l_{m}}), \tag{4}\]  
where \(\mathcal{T}_{l_{m}}\), \(C_{l_{m}}\), \(I_{l_{m}}\), \(\mathcal{A}_{l_{m}}\), and \(Q_{l_{m}}\) denote the trustworthiness, confidentiality, integrity, availability, and quality of a link \(l_{m}\). The quality of a link refers to the error rate of the link. The function \(f(\cdot)\) in Equation (4) is similar to that in Equation (3). In Equation (3), the trustworthiness of a node can be calculated with confidentiality, integrity, and authenticity metrics, which are classical yet fundamental components for assessing the trustworthiness of a node.