## 8 IoMT Security Model
### Authentication Model  
[PERSON] and [PERSON] [80] presented the smart service authentication (SSA) framework to cross-examine the communication entities' common secret session key and improve mutual authenticity. It provides an authentic signature for conducting encrypted transfers between communication nodes and ensuring enhanced data security between the patients and physicians. Formal and informal verifications were used to investigate the security attributes. The suggested SSA framework has been implemented utilizing a Field Programmable Gate Array (FPGA) and Moteiv TMote Sky-Mote to demonstrate the system's security and performance efficiency. The importance of the SSA framework model's ability to withstand security threats such as health-report forgery, health-report reveal, server-spoofing, and so on is demonstrated by formal and informal security analysis. As a result, it is shown to be a good fit for the telecare medical information system (TMIS).  
[PERSON] et al. [13] proposed a secure communication scheme for medical applications utilizing Attribute-Based Encryption (ABE) for authentication in a Heterogeneous Network (HetNet) at the network layer. Health-related information is protected using ABE. This not only reduces transmission costs, but also protects health data from intruders [21]. It incorporates a third-party server that assists in the authentication and storage of patient data. A high-level protocol-specification language (HLPSL) is used to implement the complete security method. The AVISPA automated tool is used to validate the system codes. However, in this scenario, the users communicate through a third-party trusted authority. If this third party is hacked, all the data become subject to hostile attacks.  
[PERSON] et al. [81] proposed a lightweight and robust authentication scheme based on the physical unclonable function (PUF) for IoMT. This technique does not save any data from IoMT devices in server memory. In this mechanism, the devices are completely authenticated within 1.2 to 1.5 s. A hybridized oscillator arbiter PUF is used to accomplish system validation. Based on the PUF used during system validation, the number of keys used for authentication was around 240. As the technique is lightweight, it may be used in a variety of designs to enable scalability and resilience. However, the system failed to verify that the client could authenticate the server's communications.  
[PERSON] et al. [82] proposed a multimodal biometric identification approach for IoMT. The system's effective matching technique was based on the Fishers vector's secondary calculation (FV). In addition, the system made use of three biometric techniques: finger vein, fingerprint, and face. These methods are combined at the feature level. Again, the system used a bogus feature in the feature fusion process, which often occurs in the real world. The liveness detection is added to the system, which uses DCT (Discrete Cosine Transform) to determine whether the image is genuine or false, and then removes the fake image to improve the system's robustness. The developed framework shows a relatively higher recognition rate. When compared to unimodal biometric systems, which are particularly important for an IoMT platform, it provides superior security. However, the system's accuracy ratings still remain low.