4. A Sustainable Blockchain and Asymmetric Broadcast Encryption-Based Secure E-Healthcare System

The value of healthcare records has skyrocketed due to the emergence of many new diseases and the ongoing pandemic situations. With these healthcare records spread across numerous healthcare provider entities in various locations, it has become time-consuming to manage them in physical form. Consequently, there is a growing need to transition to electronic healthcare records (EHRs). However, the current approach of managing EHRs at the centralized level creates a single point of failure and exposes users to numerous security risks which include amateur-level attacks and data breaches orchestrated by adversaries. Handling electronic health records from the Internet of Medical Things(IoMT) poses significant challenges due to the sensitive information involved, which makes it a prime target for attackers. Furthermore, managing modern healthcare systems is complex and expensive, demanding highly secure storage space. The recent COVID-19 pandemic has inflicted unprecedented costs and human suffering on a scale never seen before in the modern world. As long as diseases continue to resurface, we must strive to slow down pandemics by leveraging information systems empowered by new IT technologies. Blockchain technology emerges as one potential solution for achieving this goal. By enhancing health record management, blockchain can address these problems. Its rising popularity has sparked extensive research into different transaction schemes that specialize in privacy preservation across various fields. However, the public nature of blockchain, which exposes transaction information, introduces significant privacy risks. Therefore, it is crucial to construct an efficient scheme that is flexible in nature and ensures privacy preservation of transaction contents and reliable auditability, aspects that previous works have failed to adequately address. We propose a framework of broadcast encryption and a specific instance to provide conditional data access control. It relies on a specific dedicated asymmetric-key-based broadcast encryption scheme, which stores user encrypted credentials for the blockchain conditional data access control. Simultaneously, conditional access of the encrypted data that is stored in an off-chain source of the data is applicable to encrypted data. The blockchain environment facilitates interactive communication between users of data and data providers, providing the necessary data access control information. Our proposed solution is based on a blockchain enabled privacy-preserving transaction construction that utilizes an efficient asymmetric-key broadcast encryption method. By implementing this approach, we aim to overcome the limitations of previous works and ensure secure and private handling of healthcare transactions within the blockchain ecosystem.