Protecting metadata privacy in blockchain-based EHR systems: A group addressing structure

With the rapid advancement of Healthcare Information Technology (HIT), the volume of medical data has increased exponentially, creating a critical need for secure and accurate storage and transmission solutions. A serious challenge in this area is ensuring robust privacy protection. While numerous studies have explored the use of blockchain technology for securely sharing electronic health records (EHR), most have focused solely on safeguarding the content of EHRs. However, the privacy of metadata associated with EHRs stored on blockchain has largely been overlooked. In this paper, first, we examine how exposing EHR metadata on the blockchain can lead to privacy breaches. We analyze this vulnerability through a review of various studies, highlighting the risks associated with publicly accessible metadata in decentralized networks. Second, we propose a solution by introducing modifications to the blockchain address structure and implementing group addressing to enhance metadata privacy. To achieve this, we present a group signature protocol designed to facilitate secure group addressing in blockchain networks. Finally, the proposed group signature is evaluated against six existing models, demonstrating its effectiveness in mitigating privacy risks while maintaining the core functionalities of blockchain systems.