## 2 Related Works  
### Blockchain-Based Patient Records Tracking Systems (BPHRS)  
Blockchain technology has emerged as a leading trend for supporting distributed applications by removing the need for a reliable third party and guaranteeing stored data's integrity, validity, non-repudiation, and accountability [13; 36]. Its various network types--public [18], private [20], hybrid [19], and consortium [12]--provide flexible solutions for managing PHRs, offering secure and transparent data management that enhances privacy, access control, and interoperability across healthcare systems. Numerous studies [3; 12; 26; 27; 28; 29; 30; 31] have examined the advantages of utilizing blockchain technology in patient record-tracking systems, emphasizing safe access to medical records, authorization, and authentication. [PERSON] et al. [37] highlighted the growing concern regarding potential risks and vulnerabilities in blockchain-based PHR systems and the need to carefully evaluate their scope and effects on patient data. [PERSON] et al. [3] proposed BPHRS-Healthblock, an architecture that enhances the security and privacy of PHRs by leveraging blockchain technology, decentralized databases, and access control mechanisms. A potential constraint of this study could be the requirement for additional verification of the scalability and interoperability of the proposed system in real healthcare environments, in addition to performance assessment parameters. [PERSON] et al. [12] created smart contracts based on the Ethereum blockchain to provide patients with decentralized,immutable, transparent, traceable, trustworthy, and secure control over their data. The proposed approach securely retrieves, stores, and distributes patient medical data by utilizing trusted reputation-based re-encryption oracles in conjunction with decentralized storage of IPFS. However, beyond the provided evaluation criteria, additional validation of the suggested solution's scalability and interoperability in various healthcare environments may be required, which could be a significant drawback of this study. [PERSON] et al. [21] introduced a novel design and access control algorithm to enhance data protection while ensuring patient data privacy and security within a PHR system by eliminating central authority and single points of failure and leveraging Hyperledger blockchain technology. Despite the utilization of Hyperledger for safeguarding privacy and security, potential system flaws or vulnerabilities may remain, potentially enabling unauthorized access by hackers to patient data, thereby jeopardizing the system's integrity. BlockMedCare, created by [PERSON] et al. [25], is an IoT and Blockchain integration that allows for secure remote patient monitoring for chronic diseases. It guarantees security by integrating Blockchain and re-encryption, scalability through an off-chain IPFS database, and faster processing times with Ethereum-based proof of authority. While BlockMedCare offers benefits, it may have deployment and interoperability problems that necessitate carefully assessing compatibility with existing healthcare infrastructures. The Hyperledger blockchain-based HapiFabric system was proposed by [PERSON] et al. [26] to improve the security, scalability, and dependability of medical operations. It is tailored for patient-centric telemedicine. Prioritizing the requirements of patients, HapiFabric also helps healthcare providers by minimizing needless travel and improving time management while upholding the standard of treatment. However, one limitation is the restricted accessibility of medical records across all locations. [PERSON] et al. [28] introduced HSHB, a hybrid blockchain-based strategy for health data sharing that adapts to different sharing entities' requirements by utilizing alliances and private chains. It implements the health data access control policy to protect entities from interference and uses efficient query algorithms to obtain previous health data.