With the proliferation of intelligent healthcare systems, patients’ Personal Health Records (PHR) generated by the Internet of Medical Things (IoMT) in real-time play a vital role in disease diagnosis. The integration of emerging blockchain technologies significantly enhanced the data security inside intelligent medical systems. However, data sharing across different systems based on varied blockchain architectures is still constrained by the unsolved performance and security challenges. This paper constructs a cross-chain data sharing scheme, termed MedExChain, which aims to securely share PHR across heterogeneous blockchain systems. The MedExChain scheme ensures that PHR can be shared across chains even under the performance limitations of IoMT devices. Additionally, the scheme incorporates Cryptographic Reverse Firewall (CRF) and a blockchain audit mechanism to defend against both internal and external security threats. The robustness of our scheme is validated through BAN logic, Scyther tool, Chosen Plaintext Attack (CPA) and Algorithm Substitution Attack (ASA) security analysis verification. Extensive evaluations demonstrate that MedExChain significantly minimizes computation and communication overhead, making it suitable for IoMT devices and fostering the efficient circulation of PHR across diverse blockchain systems.

With the widespread adoption of medical informatics, a wealth of valuable personal health records (PHR) has been generated. Concurrently, blockchain technology has enhanced the security of medical institutions. However, these institutions often function as isolated data silos, limiting the potential value of PHRs. As the demand for data sharing between hospitals on different blockchains grows, addressing the challenge of cross-chain data sharing becomes crucial. When sharing PHRs across blockchains, the limited storage and computational capabilities of medical Internet of Things (IoT) devices complicate the storage of large volumes of PHRs and the handling of complex calculations. Additionally, varying blockchain cryptosystems and the risk of internal attacks further complicate the cross-chain sharing of PHRs. This paper proposes a scheme for sharing PHRs across heterogeneous and interoperable blockchains. Medical IoT devices can encrypt and store real-time PHRs in an InterPlanetary File System, requiring only simple operations for data sharing. An enhanced proxy re-encryption(PRE) algorithm addresses the differences in blockchain cryptosystems. Multi-dimensional analysis demonstrates that this scheme offers robust security and excellent performance.

Blockchain systems encompass many distinct and autonomous entities, each utilizing its own self-contained identity authentication algorithm. Unlike identity authentication within a singular blockchain, cross-chain scenarios demand special attention due to their pivotal role in enabling the acknowledgment of users’ identities across diverse domains. This capability is the foundational prerequisite for the circulation of resources across different chains. Consequently, the central challenge for cross-chain systems lies in establishing mutual recognition and trust in users’ digital identities. This paper proposes a Multi-User Proxy Re-Signature (MU-PRS) algorithm, facilitating the cross-chain conversion of signatures from multiple users. Concurrently, This paper propose the Multi-Notary Signature Conversion (MN-SC) mechanism, designed to address the challenge posed by disparate system mechanisms across blockchains during cross-chain authentication. Leveraging the MU-PRS algorithm and MN-SC mechanism, we present a Multi-User Cross-Chain Authentication Scheme (MU-CCAS) within a heterogeneous blockchain environment. This scheme enables the verification of identities of multiple cross-chain users through a single signature verification. This innovative approach not only addresses the centralization issues inherent in third-party cross-chain authentication but also significantly enhances the efficiency of identity authentication. The evaluation results demonstrate MU-CCAS’s superior security over existing solutions in three dimensions: BAN logic, Scyther verification, and security attribute analysis. Additionally, it establishes that MU-PRS and MU-CCAS have low computational overhead, easy implementation, and excel in algorithm, scheme, and cross-chain performance. Overall, our work provides a robust and efficient framework for cross-chain authentication, addressing centralization challenges and enhancing digital security.