## 4 Proposed System and Architecture  
This paper proposes a novel secure and lightweight privacy-safeguarding IoMT system, known as Secure-by-Design Real-Time IoMT Architecture for e-Health Population Monitoring (RTPM). This kind of system is best fit for monitoring well-being in two-fold, i.e., local monitoring (care home, hospital, etc.) and remote monitoring, as shown in Figure 3. The proposed IoMT device can collect diverse sensory information (movement, temperature, humidity, light, pressure, air quality, picture, or video) and display messages with LCDs, buzzers, and LEDs. The proposed RTPM is a secure-by-design solution that protects the data source (IoMT device), securely authenticates every participating IoMT device,  
Figure 3: Proposed balanced system requirement over device limitation, security and performance.  
safeguards data transmission channel from unauthorised access, ensures non-repudiation, protects data from MAC spoofing, conducts secure key management and authorises every user participating in the system to support auditing and accounting. Thus, the proposed system addresses all the key security issues about data confidentiality, data integrity, and data availability. The proposed system has the following key security and network features:  
Data confidentiality: The communication and interaction between the IoMT client and the IoMT server (and the web server) are secured through a combination of RSA, AES, and SHA algorithms.  
Data Integrity: All data generated by the IoMT client are signed, and the integrity of the data is preserved using SHA 256.  
Authorisation, Authentication, and Access Control: User registration is conducted via the web server securely, and authorisation is needed to receive unique IDs for device authentication and for controlling access.  
System Recovery and Self-Healing Network: If the client is disconnected, the last data block sent is remembered, and the data from the last point of failure continue to be sent automatically when the application is restarted.  
Privacy-based Alerting Methods: The system can securely alert the user's selected individual using registered emails, e.g., doctor, career, friends, or family (via email), when the condition of a monitoring outcome is not normal (e.g., when their body temperature is too high, or when the air quality of the room is bad).  
System Monitoring and Evidence Collection: The system logs every exception, error, and abnormal event, e.g., lifting the IoMT device, coming close to the monitoring system, etc., to monitor physical intrusion.  
Data Visualisation: The IoMT server is integrated with a web server, and the data are visualised for easy access. All the registered IoMT devices can be monitored from anywhere and at any time.  
In addition, this paper conducts an in-depth performance-comparative study of the secure integration of the interaction and engagement of the IoMT client with the user, IoMT server, and the web server. This study enlightens the research community on what key sizes are appropriate for building a secure IoMT system, how to securely register users and devices, and what kind of data can be securely transmitted in real time.