###### Abstract  
The Internet of Medical Things (IoMT) has risen significantly in recent years and has provided better quality of life by enabling IoMT-based health monitoring systems. Despite that fact, innovative security mechanisms are required to meet the security concerns of such systems effectively and efficiently. Additionally, the industry and the research community have anticipated that blockchain technology will be a disruptive technology that will be able to be integrated into innovative security solutions for IoMT networks since it has the potential to play a big role in: (a) enabling secure data transmission, (b) ensuring IoMT device security, and (c) enabling tamper-proof data storage. Therefore, the purpose of this research work is to design a novel lightweight blockchain-based security architecture for IoMT-based health monitoring systems leveraging the features of the Hyperledger Fabric (HF) Platform, its utilities. and its lightweight blockchain nature in order to: (i) ensure entity authentication, (ii) ensure data confidentiality, and (iii) enable a more energy-efficient blockchain-based security architecture for IoMT-based health monitoring systems while considering the limited resources of IoMT gateways. While security mechanisms for IoT utilizing HF do exist, to the best of our knowledge there is no specific HF-based architecture for IoMT-based health monitoring systems. Internet of Medical Things; blockchain; hyperledger fabric; healthcare +
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so that the pressing security challenges of IoMT-based health monitoring systems, relying on IoMT networks, can be addressed in an effective and efficient manner. This must be performed while taking into consideration the inherent limitations of the IoMT networks and devices, due to their resource-constrained characteristics and the centralized nature of IoMT-based health monitoring systems, before these systems gain the trust of all involved stakeholders and reach their full potential in the healthcare market [6; 8; 11]. To this end, blockchain technology has been foreseen by the industry and research community as a disruptive technology that can be integrated into novel security solutions for IoMT-based health monitoring systems in order to: (a) enable IoMT devices to transmit data to each other in a secure manner (e.g., tamper-proof transmission of medical data, no risk of DoS attacks) [3], given its decentralized, autonomous, and cryptographically secure nature, (b) ensure IoMT device security, and (c) enable tamper-proof data storage [12; 13; 14]. However, despite the significant benefits that the integration of blockchain technology can bring to the current, centralized IoMT-based health monitoring systems by addressing security challenges related to single point of failure issues and data storage, the resource-constrained IoMT devices of these systems are still unable to afford complex and high energy-consuming blockchain operations (e.g., the mining process in Proof of Work (PoW)) because of their limited processing power, storage capacity, and battery life [15; 16; 17; 18]. Consequently, it is essential for lightweight blockchain-based security mechanisms to be applied so that they can be efficiently supported by the resource-constrained IoMT devices within IoMT-based health monitoring systems. However, so far, and to the best of our knowledge [19], there are only few works on blockchain-based authentication and authorization mechanisms as well as on blockchain-based Intrusion Detection Systems that can be considered for protecting IoMT-based health monitoring systems, demonstrating the lack of proper works on lightweight blockchain-based security for IoMT-based health monitoring systems.