# Development and Pilot-Test of Blockchain-Based MyHealthData Platform
## 3 Results  
Figure 2 shows the main flow of MyHealthData services. When the user agrees to the terms and conditions and goes through the self-verification process, the MyHealthData membership registration is completed by setting a password for using the app and entering some key information.  
Data was requested from medical institutions in the form of RESTful API, received, and linked. Health information, such as health checkup results and test details, is visualized and expressed (Figures 3 and 4).  
Figure 4: Inquiry of medical history and receipts to claim private insurance.  
Figure 3: Data visualization through the app.  
Figure 2: Main flow of service.  
A total of 1228 individuals signed up for the MyHealthData service (SNUH 976, Chaum Clinic 252, respectively). The criteria for service sign-up were for subscribers who performed self-authentication in the MyHealthData app. The most used service was \"inquire about medical and health checkup records\", followed by \"health coaching\", \"check conditions of participation in clinical research\", and \"claim private insurance\", respectively (Table 1).  
Inquire about medical and health checkup records  
Users were able to download their MyData stored in SNUH from the MyHealthData app to their mobile phone. MyData was provided in json or csv file formats. Data could be shared selectively according to the needs of the users. Proof of data authenticity is verified thorough the blockchain; when healthcare data is sent through the MyHealthData app, the hash value of the data is recorded in the blockchain and proof of authenticity is confirmed by comparing hash values.  
The health coaching service calculated various health care parameters (exercise amount, calories burned, exercise time, etc.) using measured lifelog data. Lifelog data was obtained in two ways. The user directly entered the anthropometric data, such as height, weight, waist circumference, and blood pressure, or obtained it by integrating information from personal mobile built-in lifelog apps, such as HealthKit [25] (healthcare and fitness application for iOS) or S-Health [26] (healthcare and fitness application provided by Samsung). This service reflected health needs by comparing users' lifelog and medical data with the average population's data. Physical activity volume and frequency could be provided to the attending physician and enabled more accurate diagnosis.  
Check conditions of participation in clinical research  
The app showed the ongoing clinical trials from a list provided by the Clinical Trial Center of SNUH. Users could find out whether they could apply to a clinical trial based on their health records. Users also could figure out the eligibility criteria for each clinical trial and compare the eligibility criteria to their PHR.  
Claims through the app  
Users could use the app for submitting claims to their private insurance. Receipts and medical certificates could be sent from the hospital to the app. All medical information was encrypted and stored in the app, and users could select and send the medical history which they wanted to claim.