7.1 DApp architecture and components

Decentralized applications (DApps) are revolutionizing how we interact with digital services. They combine smart contracts, user-friendly interfaces, and decentralized storage to create trustless, transparent systems. Unlike traditional apps, DApps operate on blockchain networks, eliminating single points of failure.

DApp architecture consists of interconnected layers that work together seamlessly. The user interface communicates with smart contracts, which interact with the blockchain and decentralized storage. This structure ensures data integrity, censorship resistance, and automatic execution of predefined conditions, making DApps more secure and resilient than centralized alternatives.

DApp Architecture and Components

Components of DApp architecture

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• Smart contracts
  • Self-executing contracts with agreement terms directly written into code
  • Stored and replicated on a blockchain network (Ethereum, EOS)
  • Automatically execute when predetermined conditions are met
  • Ensure trust, transparency, and immutability in transactions
• Frontend interfaces
  • User-facing component of a DApp allows interaction with smart contracts and blockchain
  • Built using web technologies like HTML, CSS, and JavaScript
  • Communicate with the blockchain through APIs or libraries (Web3.js)
  • Enable users to view and interact with DApp functionality
• Decentralized storage
  • Distributed file storage systems used to store and retrieve data in a DApp
  • Examples include IPFS (InterPlanetary File System) and Swarm
  • Ensure data integrity, availability, and censorship resistance
  • Files are split into smaller pieces, encrypted, and distributed across multiple nodes
  • Prevents data loss and enables decentralized access to information

Interactions in DApp stack

• User interface layer
  • Users interact with the DApp through a web browser or mobile app
  • Communicates with the smart contract layer via APIs or libraries (Web3.js)
  • Sends user requests and receives responses from the backend
• Smart contract layer
  • Contains the business logic and rules of the DApp
  • Interacts with the blockchain layer to execute transactions and store data
  • Emits events to notify the user interface layer of state changes
  • Enables trustless execution of predefined conditions
• Blockchain layer
  • Underlying distributed ledger technology (Ethereum, EOS, TRON)
  • Provides a decentralized, immutable, and transparent record of transactions
  • Ensures consensus among network participants and prevents double-spending
  • Securely stores smart contract code and related data
• Decentralized storage layer
  • Stores and retrieves data required by the DApp (user info, media files)
  • Integrates with the smart contract layer to ensure data availability and integrity
  • Enables decentralized data storage and reduces reliance on centralized servers
  • Utilizes distributed systems like IPFS or Swarm for resilient storage

DApps vs centralized web applications

• Decentralization
  • DApps: Decentralized, with no single point of control or failure
  • Traditional apps: Centralized, controlled by a single entity (company, organization)
• Backend infrastructure
  • DApps: Utilize blockchain networks and smart contracts for backend logic
  • Traditional apps: Rely on centralized servers and databases
• Data storage
  • DApps: Employ decentralized storage solutions (IPFS, Swarm)
  • Traditional apps: Store data on centralized servers or cloud platforms (AWS, Google Cloud)
• Trust and transparency
  • DApps: Transactions and data are transparent and verifiable on the blockchain
  • Traditional apps: Users must trust the central authority to manage data and transactions
• Fault tolerance
  • DApps: Resilient to node failures due to the distributed nature of the blockchain
  • Traditional apps: Vulnerable to single points of failure in centralized infrastructure

Design of basic DApp architecture

Example use case: A decentralized voting application

1. User interface
   • Web-based or mobile app for users to register, authenticate, and cast votes
   • Displays voting results and other relevant information
   • Provides an intuitive and user-friendly experience
2. Smart contracts
   • Voting contract: Manages the voting process, including voter registration, vote casting, and tallying
   • Token contract: Handles the distribution and management of voting tokens (if applicable)
   • Ensures transparency, immutability, and fairness in the voting process
3. Blockchain network
   • Ethereum blockchain to execute smart contracts and store voting data securely
   • Ensures transparency, immutability, and tamper-resistance of the voting process
   • Enables decentralized consensus and prevents vote manipulation
4. Decentralized storage
   • IPFS to store and retrieve voter information, candidate profiles, and other relevant data
   • Ensures data availability and integrity while maintaining decentralization
   • Prevents data censorship and enables public access to voting information
5. Oracle services (optional)
   • Provide external data feeds to the smart contracts, such as identity verification or real-world event outcomes
   • Enable the DApp to interact with data outside the blockchain ecosystem
   • Enhance the functionality and reliability of the voting process