System Architecture Document: Decentralized Digital Notary Service

1. Introduction

This document outlines the system architecture for the Decentralized Digital Notary Service built on the Stellar blockchain using Soroban smart contracts. The service aims to provide a secure, transparent, and tamper-proof notarization solution for digital documents.

2. System Overview

The Decentralized Digital Notary Service consists of the following main components:

1. User Interface (Frontend)
2. Application Server (Backend)
3. Soroban Smart Contract
4. Stellar Blockchain Network
5. IPFS Storage (Optional)

3. Component Description

3.1 User Interface (Frontend)

• Technology: React.js
• Purpose: Provides a user-friendly interface for document upload, notarization, and verification.
• Key Features:
  • Document upload and hashing
  • Notarization request initiation
  • Verification request handling
  • Display of notarization proofs and verification results

3.2 Application Server (Backend)

• Technology: Node.js with Express.js
• Purpose: Handles API requests from the frontend, interacts with the Soroban smart contract, and manages user authentication.
• Key Features:
  • RESTful API endpoints
  • User authentication and management
  • Integration with Stellar SDK for blockchain interactions
  • Document hash generation and validation

3.3 Soroban Smart Contract

• Technology: Rust
• Purpose: Implements the core notarization and verification logic on the Stellar blockchain.
• Key Features:
  • Notarization function to store document hashes
  • Verification function to check the existence of notarized documents
  • Timestamp recording for each notarization

3.4 Stellar Blockchain Network

• Purpose: Provides a decentralized, immutable ledger for storing notarization records.
• Key Features:
  • Consensus mechanism for transaction validation
  • Decentralized storage of notarization data
  • Public verifiability of transactions

3.5 IPFS Storage (Optional)

• Purpose: Offers decentralized storage for documents if users choose to store the full document.
• Key Features:
  • Content-addressed storage
  • Decentralized file system
  • Integration with main application for document retrieval

4. System Interactions

1. Notarization Process:
   1. User uploads document through the frontend.
   2. Frontend generates a hash of the document.
   3. Backend receives the hash and initiates a transaction with the Soroban smart contract.
   4. Smart contract stores the hash and timestamp on the Stellar blockchain.
   5. Transaction result is returned to the backend and then to the frontend.
   6. Frontend displays the notarization proof to the user.
2. Verification Process:
   1. User uploads a document for verification through the frontend.
   2. Frontend generates a hash of the document.
   3. Backend receives the hash and queries the Soroban smart contract.
   4. Smart contract checks the Stellar blockchain for the existence of the hash.
   5. Verification result is returned to the backend and then to the frontend.
   6. Frontend displays the verification result to the user.
3. IPFS Integration (Optional):
   1. If the user chooses to store the document, the frontend sends the document to the backend.
   2. Backend uploads the document to IPFS and receives a content identifier (CID).
   3. The CID is stored along with the document hash in the Soroban smart contract.

5. Data Flow Diagram

6. Security Considerations

1. Data Encryption: All communications between components will use HTTPS/TLS encryption.
2. Authentication: JWT-based authentication for user sessions.
3. Smart Contract Security: Rigorous testing and auditing of the Soroban smart contract.
4. Private Key Management: Secure storage and handling of Stellar account private keys.
5. Rate Limiting: Implement API rate limiting to prevent abuse.

7. Scalability Considerations

1. Horizontal Scaling: Design the backend to be stateless, allowing for easy horizontal scaling.
2. Caching: Implement caching mechanisms for frequently accessed data.
3. Database Indexing: Optimize database queries with proper indexing.
4. Load Balancing: Use load balancers to distribute traffic across multiple server instances.

8. Monitoring and Logging

1. System Monitoring: Implement comprehensive monitoring for all system components.
2. Error Logging: Centralized error logging and alerting system.
3. Performance Metrics: Track and log key performance indicators.
4. Audit Trail: Maintain a detailed audit trail of all notarization and verification activities.

9. Disaster Recovery and Backup

1. Regular Backups: Implement automated, regular backups of all critical data.
2. Failover Mechanisms: Design redundancy and failover mechanisms for critical components.
3. Data Replication: Use data replication techniques to ensure data integrity and availability.