## 3 Comparative Analysis of the Existing Hash Chain-Based Authentication Approaches
### Definitions of Additional Tactical Security Requirements in VMF  
The following additional security requirements are predefined and analyzed based on general requirements in the existing VMF standards and various national defense documents [29; 30]:* **Configuration of keyless point (CKP) (Q)--**Because the hash chain-based authentication with a T-OTP value is used in a rapidly changing battlefield environment, authentication in a VMF-based CNR must be able to verify friendly tactical ad hoc networks in reliable cell planning areas and warfare networks, thereby necessitating robustness against authentication data loss. In addition, to reduce the regular authentication flow, related network overhead and the security cost of server storage after adjusting the initial tactical network, the system is configured to exclude the key ownership stage in one of the two terminals using the authentication algorithm and scheme side. Interference from a variety of environmental variables and wireless jitter must also be considered [31; 32];
* **Low latency (LL) (Q)--**To rapidly conduct tactical operations and insert this scheme in wireless static terminals, the entire initial authentication process of VMF must be quickly completed. Moreover, to secure the robustness of military-based adaptive strategies [33] in line with developing network technology trends, components of latency-related requirements, such as time-to-transmit, time-to-preprocessing, time-to-retransmission, and bias or noise in battlefield [34; 35], based on general parameters in VMF, are reflected and must be defined [36; 37; 38; 39];
* **Robustness to authentication attack (RA) (Q)--**Security against active and passive internal and external authentication attacks on random nodes in VMF-based CNRs is necessary, which can be achieved using various defensive mechanisms, such as preventing the reuse of keys in hash chain- and state-based exception handling. In particular, the hash chain-based authentication system including a T-OTP value must be configured to minimize the impact of various ad hoc network-based wireless authentication attacks, such as rushing attacks [40] wormhole, blackhole and sinkhole attacks, jellyfish, flooding and fragmentation attacks, man-in-the-middle (MITM), eavesdropping and sniffing [41; 42; 43; 44; 45]. Specifically, considering the military security requirements, the resistance capabilities should focus on replay, MITM, and Byzantine authentication attacks. * **Low authentication overhead in limited networks (LAO) (Q)--**To secure interoperability across hierarchical limited-resource CNRs and connected tactical terminals with low specifications, it is necessary to minimize the authentication overhead of the computation and network transactions based on the purpose of VMF standards. In addition, unnecessary transmission and energy consumption must be reduced through exception handling, punishment, and the monitoring of participating nodes in VMF-based closed CNRs, thereby achieving higher efficiency in limited battlefields. Furthermore, it is necessary to enable rapid decision-making and provide high-quality real-time combat environment features [46];
* **Re-authentication and revocation for operations (RR) (Q)--**Re-authentication and topology updation processes must be provided to ensure that new nodes continue to participate as legitimate nodes even after the initial authentication is completed, re-establish the reliability of internally authenticated nodes, and prevent authentication attacks in an environment where intrusions from enemy forces can lead to theft and damage. It is also necessary to develop immediate authentication rejection and routing-based removal processes for the detected hostile nodes in hash chain-based authentication, including a T-OTP value, and identify internal malfunctioning nodes through an online-based culprit recognition and detection mechanism.