BAPS: a blockchain-assisted privacy-preserving and secure sharing scheme for PHRs in IoMT

Internet of Medical Things (IoMT) has gradually become the main solution for smart healthcare, and cloud-assisted IoMT is becoming a critical computing paradigm to achieve data collection, fine-grained data analysis, and sharing in healthcare domains. Since IoMT data can be frequently shared for accurate diagnosis, prognosis prediction, and health counseling, how to solve the contradiction between data sharing and privacy protection for IoMT data is a challenge problem. Besides, the cloud-assisted medical system is still at risk of a single point of failure and usually suffers from poor scalability and large response delay. Hence, we propose a blockchain-based privacy-preserving and secure sharing scheme for IoMT data, named BAPS. In BAPS, the Interplanetary File System (IPFS) is adopted to store encrypted records. Then, a non-interactive zero-knowledge proof protocol is employed to verify whether the stored data meets the specific request from data requesters without disclosing personal privacy. Moreover, we combine cryptographic primitives and decentralized smart contracts to achieve user anonymity. Finally, we leverage blockchain and proxy re-encryption to achieve fine-grained sharing of healthcare data. Security analysis indicates that this scheme meets the expected security requirements. The computational cost of BAPS is reduced by about 6% compared to state-of-the-art schemes, while the communication overhead is reduced by about 8%. Both theoretical analysis and experiment results show that this scheme can realize privacy-preserving and secure data sharing with acceptable computational and communication costs.