Decentralized Electronic Health Record (EHR) System

Overview

This project is a decentralized Electronic Health Record (EHR) management system built using:

• Solidity Smart Contracts
• Ethereum Blockchain
• IPFS (InterPlanetary File System)
• ethers.js
• MetaMask
• Angular
• Local Anvil Node

The system enables secure and decentralized management of:

• Patients
• Doctors
• Appointments
• Medical Records
• Access Permissions

The architecture follows an IPFS-first design where sensitive medical data is stored off-chain while only essential references and permissions are maintained on-chain.

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Objectives

The main goals of this project are:

• Eliminate centralized health record dependency
• Ensure tamper-resistant medical history
• Enable decentralized ownership of health records
• Provide secure doctor-patient access control
• Reduce data duplication and unauthorized access
• Learn Web3-based healthcare architecture

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Technology Stack

Technology	Purpose
Solidity	Smart Contract Development
Ethereum	Blockchain Network
Anvil	Local Ethereum Development Node
Hardhat	Smart Contract Tooling
ethers.js	Blockchain Interaction
MetaMask	Wallet Authentication
IPFS	Decentralized File Storage
Angular	Frontend Application
TypeScript	Frontend Logic

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System Architecture

Blockchain Stores

The blockchain stores:

• Wallet addresses
• User roles
• Appointment references
• Medical record references
• Access permissions
• IPFS content identifiers (CIDs)

IPFS Stores

IPFS stores:

• Patient profile metadata
• Doctor profile metadata
• Appointment metadata
• Medical record metadata
• Uploaded medical files/documents

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User Roles

Admin

Responsible for:

• Registering doctors
• Registering patients

Doctor

Can:

• View authorized patient records
• Add medical records
• Approve/reject appointments
• View appointments

Patient

Can:

• Book appointments
• Grant/revoke doctor access
• View own medical records
• Cancel appointments

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Smart Contract Modules

1. User Management

Features

• Register doctors
• Register patients
• Validate user roles

Data Stored

struct User {
    address id;
    string profileCID;
    bool exists;
}

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2. Appointment Management

Features

• Book appointments
• Update appointment status
• View appointments by user
• Admin can view all appointments

Appointment Status

• PENDING
• APPROVED
• REJECTED
• COMPLETED
• CANCELED

Data Structure

struct Appointment {
    uint256 id;
    address patient;
    address doctor;
    string metadataCID;
    uint256 appointmentTime;
    AppointmentStatus status;
    uint256 createdAt;
}

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3. Medical Record Management

Features

• Upload medical records
• Retrieve patient records
• Access-controlled record viewing

Data Structure

struct MedicalRecord {
    uint256 id;
    address patient;
    address doctor;
    string metadataCID;
    string filesCID;
    uint256 createdAt;
}

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4. Access Control

Patients can:

• Grant doctors access to records
• Revoke doctor access

Doctors can:

• Access records only when permission is granted

Permission Mapping

mapping(address => mapping(address => bool))
private doctorAccess;

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Smart Contract Design Principles

Minimal On-Chain Storage

Sensitive data is NOT stored directly on-chain.

Only:

• references
• permissions
• relationships
• metadata CIDs

are stored on blockchain.

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Single Source of Truth

Appointments and records are stored using:

mapping(uint256 => Appointment)
mapping(uint256 => MedicalRecord)

with indexed relationships for scalability.

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Access-Controlled Data Retrieval

Medical records are accessible only if:

• requester is the patient
• requester is an authorized doctor

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Workflow

Patient Registration

1. Admin registers patient
2. Patient profile uploaded to IPFS
3. CID stored on blockchain

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Doctor Registration

1. Admin registers doctor
2. Doctor profile uploaded to IPFS
3. CID stored on blockchain

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Appointment Booking

1. Patient selects doctor
2. Appointment metadata uploaded to IPFS
3. Appointment stored on blockchain

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Medical Record Upload

1. Doctor receives permission
2. Medical files uploaded to IPFS
3. CID references stored on blockchain

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Security Features

• Role-based access control
• Permission-controlled medical records
• Immutable blockchain records
• Decentralized storage
• Patient-controlled authorization

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Advantages

• Decentralized architecture
• Improved transparency
• Tamper resistance
• Reduced centralized dependency
• Better interoperability
• Patient ownership of data

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Limitations

• Blockchain transaction costs
• Public blockchain metadata visibility
• IPFS availability management
• No encryption implemented in MVP
• Limited scalability without indexing

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Future Improvements

• Encrypted IPFS payloads
• Hospital management module
• Prescription management
• Pagination support
• Event indexing
• Audit logs
• Multi-admin support
• The Graph integration
• Role-based dashboards
• JWT + Web3 hybrid auth
• File encryption and key management

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Local Development Setup

Start Complete Project Environment

Run:

./start-project.sh

This starts:

• Local Anvil blockchain
• Local IPFS node
• Frontend application
• Required development services

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Smart Contract Deployment

Option 1 — Deployment Script

Run:

./deployer.sh

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Option 2 — Hardhat Ignition Deployment

Compile Contracts

npx hardhat compile

Deploy Contract

npx hardhat ignition deploy ignition/modules/EHR.ts --network localhost

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Frontend Setup

Install dependencies:

npm install

Run Angular frontend:

ng serve

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Project Structure

contracts/
├── EHR.sol

frontend/
├── src/

ignition/
├── modules/
│   └── EHR.ts

scripts/
├── deployer.sh
├── start-project.sh

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Conclusion

This project demonstrates a decentralized healthcare record management system using blockchain and IPFS technologies. The architecture prioritizes:

• decentralized ownership
• secure access control
• scalable smart contract design
• minimal on-chain storage

The implementation serves as a strong MVP foundation for future enterprise-grade decentralized healthcare applications.