A Blockchain and Chameleon Hash-Based Mechanism for Secure Incremental Updates and Sharing of Medical Data

Abstract

Background: The inherent immutability of traditional blockchain technology fundamentally conflicts with the need for dynamic updates and secure sharing of medical data. Existing editable blockchain solutions also face limitations in update efficiency, key management security, and cross-institutional privacy protection. Objective: This paper aims to design a novel architecture that integrates chameleon hash with a permissioned blockchain to achieve secure, efficient, and auditable incremental updates and controlled sharing of medical data. Methods: We propose a hybrid architecture comprising: (1) a lightweight off-chain update protocol based on chameleon hash, enabling authorized institutions to swiftly modify off-chain data using a trapdoor key while only recording lightweight credentials on the blockchain; (2) a distributed trapdoor key management mechanism based on threshold signatures, which disperses critical authority across multiple trusted medical nodes to eliminate single points of failure; and (3) cross-institutional data sharing smart contracts with privacy protection, featuring an integrated Zero-Knowledge Proof (ZKP) verification interface that allows third parties to verify data validity without accessing the original sensitive information. Results: Compared to traditional schemes, our method improves update throughput by 3.2× and reduces on-chain storage by 76%. Authorized updates and verification complete within 5 seconds in simulated cross-hospital scenarios, while distributed key management prevents unauthorized modifications. Conclusion: The proposed scheme balances dynamic updates with trustworthy auditing in medical data management. By addressing efficiency, security, and privacy limitations of existing solutions, it supports the development of a trusted, privacy-secure medical data ecosystem.