Blockchain-based architecture design for personal health record (Preprint)

BACKGROUND The importance of blockchain-based architectures for personal health record (PHR) lies in the fact that they are thought and developed to allow patients to control and at least partly collect their health data. Ideally, these systems should provide the full control of such data for the respective owner. In spite of this importance, most of the works focus more on describing how blockchain models can be used in a PHR scenario than whether these models are in fact feasible and robust enough to support a large number of users. OBJECTIVE Toward a consistent, reproducible and comparable PHR system, we build a novel ledger-oriented architecture out of a permissioned distributed network, providing patients with a manner to securely collect, store, share and manage their health data. We also emphasize the importance of suitable ledgers and smart contracts to operate the blockchain network as well as discuss the necessity of standardizing evaluation metrics to compare related works. METHODS We adopted the Hyperledger Fabric platform to implement our blockchain-based architecture design and the Hyperledger Caliper framework to provide a detailed assessment of our system under workload, ranging from 100 to 2,500 simultaneous record submissions, and using throughput and average latency as primary metrics. We also create a health database, a cryptographic unit and a server to complement the blockchain network. RESULTS Smart contracts that write on the ledger have throughputs, measured in transactions per seconds (tps), in an order of magnitude close to 10^2 tps while those contracts that only read have rates close to 10^3 tps. Smart contracts that write also have latencies, measured in seconds (s), in an order of magnitude close to 10^1 s while that only read have delays close to 10^0 s. In particular, smart contracts that retrieve, list and view history have throughputs varying, respectively, from 1,100 to 1,300 tps, 650 to 750 tps and 850 to 950 tps, impacting the overall system response if they are equally requested under the same workload. CONCLUSIONS To the best of our knowledge, we are the first to evaluate, using Hyperledger Caliper, the performance of a PHR blockchain architecture and also the first to evaluate each smart contract separately. Nevertheless, blockchain systems achieve performances far below the traditional distributed databases achieve, indicating the assessment of blockchain solutions for PHR is a major concern to be addressed before putting them into a real production.