BMPLS: Blockchain-Based Multi-level Privacy-Preserving Location Sharing Scheme for Telecare Medical Information Systems.

The sharing of patients' locations is an important part in mobile medical services and modern smart healthcare. Although location sharing based on blockchains has advantages on decentralization and openness, there is also a challenge to guarantee the security and the privacy of locations recorded in a blockchain. To this end, this paper investigates the location sharing based on blockchains for telecare medical information systems. Firstly, we define the basic requirements of blockchain-based location sharing including decentralization, unforgeability, confidentiality, multi-level privacy protection, retrievability and verifiability. Then, using order-preserving encryption and merkle tree, we propose a blockchain-based multi-level location sharing scheme, i.e. BMPLS. The analysis results show that our scheme satisfies the above requirements. Finally, the performance of our scheme is evaluated and the experiment results show that our scheme is efficient and feasible for both patients and medical workers. In a word, our scheme can be applied to realize privacy-preserving location sharing based on blockchains for telecare medical information systems.