# Trustworthiness of Situational Awareness: Significance and Quantification
## 5 Numerical Results
### Case 2: Low-Trust Information Source  
Let us consider a motion sensor (MS) that detects nearby motion (of people or objects). The MS can be a part of a wireless sensor network (WSN) and transmits its sensed information to a cluster head node (CHN) of the WSN as depicted in Figure 4. Since MS is a low-power and low-cost device, we assume that this information is transmitted in plaintext to the CHN. Further, we assume that no message hash is appended to the message. The CHN sends the plaintext information to a GN through a wired link. The gateway node is connected to RN through a wired link, which in turn is connected to a DFN through a wired link. The DFN node is connected to the CBN via a wired link (Figure 4). In the following, we first evaluate the trustworthiness of the SA information source, and each node and link along the route from the information source to the CBN, and afterwards, we evaluate the trustworthiness of MS information at the CBN. **Motion Sensor (SA Source):** Here, we calculate the trustworthiness of the MS based on Equation (1) of our proposed model (Section 4.1). We first need to obtain the scores of various metrics stipulated in Equation (1) that affect the trustworthiness of a source. In the following, we calculate the score of these metrics for this case. _Confidentiality:_ In this case, we assume that the information gathered is not encrypted but is stored in private memory, which is not accessible to unauthorized parties. Thus, the MS for this case can be assigned a confidentiality score of 0.3. For less trustworthy sources not employing standardized protocols, the score for the security metrics can be assigned based on the overall security assessment of the source. Encryption, for example, is a primary means for ensuring confidentiality, and constitutes about 70% of the confidentiality score. For our considered example, the assumption is that the information is not encrypted, which results in a 70% penalty on the confidentiality score, while the employment of private memory and storage control permits 30% of the confidentiality score, which results in an overall confidentiality score of 0.3 for the source. We note that this weightage assignment is not standard, but just a guideline, and COP designers can choose different weightage for different aspects of the confidentiality metric. _Integrity:_ In this case, the MS employs error correction code (ECC) memory to detect and correct \(n\)-bit errors in memory, but does not calculate the HMAC of the message to be transmitted to the CHN. Hence, the integrity score for MS for this case can be assigned equal to 0.2. _Authenticity:_ Since the MS in this case does not incorporate security primitives, the MS cannot be authenticated with an authentication protocol (such as the protocol in [18]), and can be assigned an authenticity score of 0. _Availability:_ Since the CBN receives data from the MS periodically, an availability score of 1 can be attributed to the MS.  
Figure 4: Quantification of trustworthiness of COP—case of low-trust information source. _Non-repudiability:_ Since the MS in this case does not sign the message with its private key nor does it encrypt the messages with its secret key, it can be ascribed a non-repudiability score of 0. _Precision:_ With the assumption that the MS can detect nearby motion with 100% precision [21], we assign it a precision score of 1. _Quality:_ The MS can obtain good quality signals regarding nearby motion, and thus its quality score can be assigned as 1. _Usability:_ The motion sensors can be installed at different places, in particular places with restricted entry, to detect nearby motion; hence, a usability score of 1 can be attributed to the MS. Since, in our model, there are eight metrics that influence the trustability of the source, we assign a weight of 0.125 (i.e., 1/8 = 0.125) to each metric, although different weights can be assigned to different metrics depending on the mission needs.