## 4 Proposed Lightweight Authentication Based on Multi-Factor Hash Chain with T-OTP in VMF
### Lightweight Authentication Processes Based on Hash Chain
#### 4.2.4 Testing of Exception Handling Flows in Specialized Military Scenarios in VMF-Based CNRs  
This phase involved testing to prove the reliability of the LSH-based multi-factor hash chain with T-OTP value schemes in CNRs, including specialized military scenarios. Certain example scenarios to test exception handling flows are as follows.  
Figure 4: Re-authentication and revocation phases.  
* **Scenario 1**: Masquerading hostile nodes for exfiltration of tactical information (Figure 5).
* **Scenario 2**: Internal friendly nodes deliberately or accidentally conspiring with malicious outsiders based on deceptive collusion attacks (Figure 6).
* **Scenario 3**: Selfish friendly nodes monopolizing limited network resources with an enemy node that has been compromised (Figure 7).  
Scenario 1 checked the maintenance power of tactical confidentiality and fraud detection of an occupied hostile node or an enemy node disguised as a friendly node (that is, when abnormal behavior is detected and recognized as a critical failure session, the LSH-based hash chain including T-OTP was used to conduct an emergent authentication between the commander of the squad and the squad members in CNR networks). In addition, when a specific abnormal node was identified as an enemy, it was removed from the tactical squad status, and the change was reflected in the CNR. Scenario 2 checked the detection and prevention of internal nodes that might conspire with unspecified hostile nodes. While the inter-connection was maintained, re-authentication was performed according to the re-authentication scheduler (periodic). Depending on the resilience of the operation, the clock cycle for the re-authentication scheme was dynamically configured according to the purpose of the tactical operation (non-periodic). When a critical failure session was recognized during the re-authentication process, the corresponding enemy node was removed from the network, and the state of the belonging squad nodes was reflected in the VMF-based CNRs. Scenario 3 checked the robustness of the network structure when removing abnormal nodes that occupied limited resources, such as low transaction for lightweight authentication or nodes that were currently not required for additional allied operations. In the event that member nodes in the squad network were changed to conduct additional tactical operations, unwanted nodes were safely removed.  
In addition to the aforementioned three scenario-based exception handling flows, attack scenarios that can be considered in limited military ad hoc-based CNR networks should reflect the characteristics of military communication environments in small-scale combat situations, for example, hierarchical high-capacity transmitter radio-net (HCTR) communication for independent battalions above brigade levels, low capacity transmitter radio-net (LCTR) communication below battalion levels, tactical mobile communication system (TMCS), and master-slave-based swarm communication. These include malicious radiowave interference in wideband network waveforms (WNW), spoofing and meaconing-based GPS jamming, advanced DoS-based operation availability violations, deceptions, and other cyber threats that can significantly impact limited tactical networks.