# Secure PBFT Consensus-Based Lightweight Blockchain for Healthcare Application
## 2 Literature Review  
Providing accurate and cost-efficient patient care has driven attention towards healthcare data management in recent years. Since then, many researchers have proposed blockchain-based approaches, mainly focusing on permission-less Bitcoin networks, but these will induce computation and communication overhead. To overcome the issues of traditional blockchain networks, [PERSON] et al. [16] proposed lightweight blockchain architecture for healthcare data management by dividing the Bitcoin network into clusters. The proposed model ensures the security and confidentiality of transactions by introducing a canal for a group of participants in the network. However, experimental results show better performance compared to the Bitcoin network, since each node must keep a local copy of the ledger, the proposed model is not suitable for memory-constrained IoT devices. Remote Patient Monitoring (RPM) is another aspect of healthcare where patients with health disorders such as COVID-19 [17], heart diseases, etc., can be treated from a remote location using the real-time data fetched by the IoT sensors. During the process, maintaining security and privacy is a challenging task. [PERSON] et al. [18] proposed blockchain-based security approaches for remote patient monitoring using IoT devices by using various lightweight cryptographic techniques such as Ring Signature and Diffie-Helman Key exchange to ensure reliable data communication over the network and storage over the cloud. Even though the blockchain has the power to resolve the issues of IoT applications, due to high computation complexity, high bandwidth overhead, and latency of the blockchain, it is unsuitable for IoT applications. However, the authors [PERSON] et al. [19] proposed an Efficient Lightweight Integrated Blockchain (ELIB) framework, aimed to resolve the security and privacy issues of the IoT by creating an overlay blockchain network. The proposed model was designed by considering three optimization aspects, i.e., Lightweight Consensus algorithm, Cerificateless Cryptography (CC), and Distributed Throughput Management Scheme (DTM). Experimental results of the proposed model outperformed in terms of energy consumption. Lightweight Scalable Blockchain (LSB) creates an overlay network consisting of multiple clusters with cluster-heads to manage the blockchain. [PERSON] et al. [20] proposed the Distributed Time-based Consensus algorithm, Distributed Trust Approach, and Distributed Throughput Management algorithm to reduce mining processing overhead and delay in an IoT application. The experimental result ensures end to end security. However, for small networks, Distributed Time-based Consensus algorithms are prone to Sybil attack. PBFT consensus is most widely used in consortium blockchain systems; however, PBFT has difficulty identifying faulty nodes in time and the randomly chosen primary node is vulnerable to attacks. Thus, to reduce the rights of faulty nodes in the voting process [PERSON] et al. [21] incorporated a reputation model in traditional PBFT consensus to detect the malicious nodes and choose the primary node. The node with a better reputation will have more chances to become a primary node. The proposed model was tested in the simulated environment, hence the experimental results show an increase in throughput, reduced delay, and decreased faulty node rate compared to traditional PBFT as the system continues to operate. However, the usage of extra data structure in the proposed model will lead to performance overhead, hence optimization techniques need to be incorporated in the future to implement it in a real-time blockchain environment. [PERSON] et al. [22] proposed a blockchain-based framework for health applications using Proof of Authentication to alert the authenticated healthcare providers using patients' health data in a secure and private manner. The cluster-based overlay networks of the proposed model reduce the network overhead and delay. [PERSON] et al.