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 signiffcantly 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 veriffcation. Extensive evaluations demonstrate that MedExChain signiffcantly minimizes computation and communication overhead, making it suitable for IoMT devices and fostering the efffcient circulation of PHR across diverse blockchain systems.

翻译：随着智能医疗系统的普及，由医疗物联网实时生成的患者个人健康记录在疾病诊断中发挥着至关重要的作用。新兴区块链技术的集成显著增强了智能医疗系统内部的数据安全性。然而，基于不同区块链架构的跨系统数据共享，仍受限于尚未解决的性能与安全挑战。本文构建了一种跨链数据共享方案，命名为MedExChain，旨在安全地实现异构区块链系统间的个人健康记录共享。该方案确保即使在医疗物联网设备的性能限制下，个人健康记录仍能实现跨链共享。此外，方案结合了密码学反向防火墙与区块链审计机制，以抵御内部与外部的安全威胁。我们通过BAN逻辑、Scyther工具、选择明文攻击与算法替换攻击的安全性分析验证，证实了本方案的鲁棒性。大量评估表明，MedExChain显著降低了计算与通信开销，使其适用于医疗物联网设备，并促进了个人健康记录在不同区块链系统间的高效流通。