Best Practices for Developing Secure Web3 Applications: Building Trustworthy DApps
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Best Practices for Developing Secure Web3 Applications: Building Trustworthy DApps
By comprehensive design, testing, and implementation, the reliability and credibility of DApps in blockchain environments can be ensured.
Navigating Web3 tides with focused insightsAuthor: Salus
Developing trustworthy DApps is crucial for establishing user trust, ensuring security, delivering a good user experience, and advancing the adoption of blockchain technology. Trustworthy DApps provide users with a secure, transparent, and decentralized environment, laying a solid foundation for the sustainable development and widespread use of blockchain technology. We will discuss the technical stack for building DApps from the following five aspects:
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Smart contract development: Ensure smart contract design follows best practices and security principles, adopting modular and scalable architectures to facilitate future upgrades and modifications.
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Smart contract testing: Conduct comprehensive unit, integration, and system testing to ensure correctness and stability. Simulate various scenarios and attacks to verify robustness and security.
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Frontend development: Build user-friendly, intuitive interfaces that securely interact with smart contracts. Implement proper validation and authorization mechanisms to protect user privacy and assets.
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Middleware development: Ensure middleware reliability and security through appropriate encryption and authentication mechanisms to safeguard user data and transactions. Middleware should also offer efficient APIs to enable seamless interaction between frontend and smart contracts.
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Smart contract deployment: Ensure correctness and integrity during deployment, including necessary data migration. Choose suitable deployment tools and networks while adhering to best practices and security guidelines.
1 Smart Contract Development
1.1 Characteristics of Smart Contracts
Smart contracts are core components of DApps, defining their logic and functionality. They are written in specialized programming languages such as Solidity, Vyper, Move, and Rust. Understanding these characteristics is essential for DApp development. Key features include:
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Atomicity: Smart contracts either execute entirely or revert completely if any part fails. This requires careful function API design, avoiding parameter overloading and handling errors cautiously.
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Error handling: Common approaches include using
requirestatements with error messages orrevertto define custom error types. These cause transaction failures and require frontends to catch and handle custom errors appropriately. -
Execution cost: Storing state consumes gas, so memory usage must be optimized. Different data structure placements incur varying costs, and state-changing functions consume gas.
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Immutability: Once deployed, smart contracts cannot be dynamically replaced or upgraded. Developers must plan for upgradeability upfront, potentially using upgradable patterns.
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Permissions and visibility: Contracts are public on the blockchain; sensitive data should never be stored on-chain. Avoid relying on block states for core business logic. Use permission controls like Ownable or AccessControl.
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Security: Security is paramount. Follow established best practices, including code security guidelines and thorough test coverage. Never assume untested code behaves correctly.
1.2 Security Practices
In DApp development, ensuring smart contract security and auditability is critical. Below are best practices and recommendations:
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Standardized development frameworks: Using standardized frameworks enhances contract credibility. These are typically maintained by experienced developers and security experts, incorporating proven, optimized code patterns. Adopting them helps avoid common vulnerabilities and leverages tested, audited code. For example, OpenZeppelin is a widely adopted framework offering secure contract templates and libraries.
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Use events for logging: Emitting events records contract execution details, enabling better tracking and auditing. Events can capture caller addresses, timestamps, input parameters, etc. Such logs are invaluable for identifying potential issues. For instance, a crowdfunding contract could emit an event per donation, recording donor address and amount, making all actions traceable.
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Implement access control: Access control restricts who can perform certain operations, requiring identity verification. In smart contracts, modifiers can enforce this by checking conditions before function execution. This ensures only authorized entities perform specific actions. For example, a voting contract might use a modifier to allow only designated addresses to vote.
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Follow the principle of least privilege: Each user should have only the minimum permissions required. In contracts, this is achieved via access control mechanisms. By limiting permissions, entities can only perform necessary actions. For example, a multi-user contract might assign different permission levels based on roles, minimizing abuse risks. Even if an account is compromised, attackers’ actions remain restricted.
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Multi-signature: Requiring multiple signatures for critical transactions adds security, mitigating risks like replay attacks and transaction malleability.
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Use timers and timeouts: Blockchain transaction times are unpredictable, exposing contracts to time-based attacks such as front-running, sandwich attacks, or random number prediction exploits. Timers schedule functions to run at specific times, reducing reliance on network timing. Timeouts limit execution duration, preventing infinite loops.
1.3 Smart Contract Upgradability
Smart contract upgrade refers to updating or modifying a contract already deployed on the blockchain. It involves changing business logic while preserving contract state. Upgrades allow developers to improve logic, functionality, or security to meet new requirements or fix bugs. However, upgrading is complex and requires extreme caution to avoid introducing vulnerabilities.
Typical steps for upgrading a smart contract include:
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Write new contract code: Developers write updated code, including improvements. The new code must undergo rigorous testing to ensure correctness and security.
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Deploy the new contract: The updated code is deployed to a new contract address. Before deployment, developers must plan how to handle data migration.
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Migrate or transfer data: If state migration is needed, developers must implement mechanisms to correctly transfer data to the new contract, often involving interactions with the old contract.
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Update contract address or interface: After successful deployment, applications and UIs interacting with the contract must be updated to point to the new address or interface.
2 Smart Contract Testing
Smart contract testing applies various methods and techniques to validate functionality, security, performance, and correctness. The goal is to identify potential issues, vulnerabilities, and bugs, ensuring the contract behaves as expected under all conditions.
2.1 Why Test?
Testing smart contracts is a vital practice in development, due to several key reasons:
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Verify contract functionality: Smart contracts execute specific tasks like fund transfers or state updates. Unit tests confirm each function works as intended, helping detect and fix bugs early.
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Ensure contract security: Contracts often manage valuable assets like cryptocurrencies. Security is critical. Unit tests help detect common vulnerabilities such as reentrancy and integer overflow, allowing timely fixes.
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Improve code quality: Writing tests encourages high-quality code. Test cases and assertions validate correctness across scenarios, improving robustness, reliability, and maintainability while reducing long-term maintenance costs.
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Support refactoring and extension: As requirements evolve, contracts may need refactoring or expansion. A comprehensive test suite ensures existing functionality remains intact, maintaining stability and simplifying future development.
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Enable continuous integration and deployment: In CI/CD environments, automated unit testing quickly identifies and resolves issues, ensuring code quality and accelerating release cycles.
2.2 What to Test?
When testing smart contracts, focus on the following areas:
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Contract functionality and behavior: Verify that functions and methods execute correctly and produce expected results. For example, a token transfer contract should correctly move funds.
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Edge cases: Test behavior under boundary conditions—minimum/maximum values, null inputs—and exceptional situations like invalid input or unauthorized access. This helps uncover hidden bugs.
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Security: This is critical. Test for potential vulnerabilities such as reentrancy, integer overflow, and unauthorized access. Security audits and targeted vulnerability testing help identify and resolve issues to protect user assets.
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Performance and scalability: Contracts must handle high volumes of transactions and users. Conduct performance and stress tests to evaluate throughput and stability under load, optimizing design accordingly.
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Integration and compatibility: If the contract integrates with other components, conduct integration tests to verify interoperability—e.g., with frontends or other contracts. Also test compatibility across Ethereum clients and network environments to ensure consistent behavior.
2.3 Testing Methods
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Unit testing: Tests individual functions or modules in isolation. Developers write test scripts simulating inputs and asserting outputs to verify expected behavior.
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Integration testing: Validates correct interaction between components. In DApp development, this includes testing contract integration with frontends or external services (e.g., blockchain nodes, databases), ensuring overall system functionality.
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Property-based testing: Focuses on whether contract behavior satisfies predefined properties—assertions that must always hold true across scenarios. Static analysis examines source code to verify properties, while dynamic analysis uses symbolic or concrete inputs to check for violations.
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Security audits: Audits involve manual code review combined with specialized tools and techniques to detect vulnerabilities and security risks. They are essential for protecting assets and user safety. For audit services, contact Salus.
2.4 Testing Tools
Foundry and Hardhat are popular tools for smart contract testing.
Foundry is a TypeScript-based smart contract development framework providing powerful tools and libraries for creating and testing Ethereum smart contracts.
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Foundry uses Mocha and Chai, two popular JavaScript testing frameworks, to write and run test cases.
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It provides built-in assertion functions to validate expected contract behavior.
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Foundry supports simulation testing, avoiding resource consumption on the live Ethereum network.
Hardhat is a powerful Ethereum development environment for writing, deploying, and testing smart contracts.
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Hardhat integrates Mocha and Chai, along with useful tools like Ethers.js and Waffle.
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It offers built-in assertion functions to verify contract behavior and state.
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Hardhat supports virtual machine testing, avoiding mainnet operations.
Using Foundry or Hardhat, you can test:
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Whether contract logic and functionality behave as expected.
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Correctness of interactions with other contracts.
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Proper handling of exceptions in various scenarios.
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Accuracy of state changes.
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Correct deployment and operation across different network environments.
These tools also offer additional features like code coverage analysis and performance testing to help developers assess and improve contract quality.
3 Frontend Development
3.1 Choosing a Frontend Framework
Selecting the right frontend framework is crucial for developing secure and reliable DApp interfaces.
3.1.1 ethers.js
ethers.js is a JavaScript library for building DApp frontends. It's a top choice for many developers, used by prominent DApp projects for Ethereum interaction and smart contract operations.
Key features include:
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Ethereum account management: Generate and manage public/private keys and addresses. Use these accounts for transactions and contract calls.
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Smart contract interaction: Offers clean APIs for interacting with Ethereum smart contracts—deploying, calling methods, reading state. Includes type-safe encoding/decoding for more reliable interactions.
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Transaction creation and signing: Easily create and send Ethereum transactions. Provides simple interfaces for constructing transaction objects and secure signing.
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Additional utilities: Supports Ether unit conversion (e.g., Wei to Ether), event handling, blockchain event subscription—making frontend development more efficient.
Advantages of ethers.js:
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Ease of use: Intuitive APIs simplify Ethereum blockchain interaction.
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Security: Securely handles private keys and transaction signing, protecting user assets.
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Rich functionality: Offers many useful utilities like unit conversion and event handling, streamlining development.
Disadvantages of ethers.js:
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Learning curve: Beginners may need time to grasp Ethereum concepts and mechanics.
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Network dependency: Functionality depends on Ethereum network availability. Network issues can disrupt DApp operation.
3.1.2 React
React is a popular frontend framework for building user interfaces. While it doesn't natively support blockchain interaction, it can be integrated via several methods:
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Web3.js: A JavaScript library for Ethereum interaction. Import into React projects to connect to Ethereum, deploy/call contracts, and send transactions.
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ethers.js: Another popular Ethereum interaction library with clean APIs for account management, contract interaction, and transaction handling.
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Blockchain explorer APIs: Services like Etherscan or Infura offer RESTful APIs to query blockchain data, transactions, and contract info.
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Wallet integration libraries: Tools like MetaMask or WalletConnect enable wallet connectivity with user-friendly interfaces and authentication.
React’s component-based architecture allows encapsulating blockchain interaction logic and UI into reusable components. This enables features like balance queries, contract calls, and event listening.
Security and privacy are paramount when integrating blockchain. Properly handle private keys, sign transactions securely, and restrict access to sensitive operations. Follow latest security best practices and blockchain standards to ensure application reliability.
Compared to ethers.js, React offers the following advantages:
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Strong ecosystem: Large developer community and extensive third-party library support. Easy to find React-integrated tools for blockchain interaction.
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Component-based development: Modular approach improves code organization, reusability, and maintainability.
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Virtual DOM: Efficient rendering via diffing previous and current states, minimizing DOM updates—ideal for handling frequent blockchain data updates.
Compared to ethers.js, React has the following disadvantages:
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Learning overhead: Unfamiliar developers must learn React fundamentals, increasing initial development time.
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Integration complexity: React’s flexibility may complicate integration with blockchain libraries, requiring extra effort to resolve compatibility issues.
In contrast, ethers.js is purpose-built for Ethereum interaction, offering direct, simple APIs and rich blockchain-specific tooling.
However, React excels in ecosystem strength, component modularity, and performance via Virtual DOM—making it ideal for large, complex applications.
3.2 Setting Up a Scaffold Project
After selecting a frontend framework, setting up a scaffold project is typical. A scaffold is a starter template providing default structure, configuration, sample code, and tools. It accelerates development by eliminating boilerplate setup and promoting best practices.
3.2.1 What Are the Main Components of a Scaffold?
A DApp scaffold typically includes:
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Smart contracts: One or more example contracts implementing application logic.
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Frontend interface: Basic UI for user interaction, built with HTML, CSS, and JavaScript.
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Test scripts: Sample tests verifying contract correctness and reliability, enabling automated testing.
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Configuration files: Settings for dev environment, contract deployment, and network connection, customizable per project needs.
3.2.2 What to Consider When Setting Up a Scaffold?
Consider blockchain connectivity, Web3 library integration, security, frontend framework setup, testing, and documentation:
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Choose the right scaffolding tool: Tools like Create React App or Vue CLI offer preset configurations for fast DApp setup.
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Configure blockchain connection: Set up node URL, port, and authentication details to enable blockchain interaction.
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Integrate Web3 library: Choose and import the appropriate Web3 library (e.g., Web3.js or ethers.js for Ethereum).
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Security considerations: Include common protections like XSS prevention and replay attack mitigation. Leverage security libraries like OpenZeppelin.
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Integrate frontend framework: Pre-configure chosen frameworks (e.g., React, Vue) for smooth operation.
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Add testing: Include test frameworks like Jest or Mocha with unit and integration tests to ensure code quality.
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Documentation and examples: Provide clear docs and sample code to help developers understand and use the project.
3.2.3 Available Scaffolds
For Ethereum-based web apps, several popular scaffolds exist. Below are three notable options:
Truffle
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Features: Full Ethereum development framework with tools for compiling, deploying, and testing smart contracts, plus interactive capabilities. Includes powerful CLI and development environment, supporting Solidity and JavaScript with rich plugin ecosystem.
Embark
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Features: Ethereum DApp framework with simple tools and CLI for development, testing, and deployment. Integrates popular frontend frameworks like React and Vue, and offers extensible plugin system.
scaffold-eth
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Features: Complete Ethereum DApp scaffold with frontend, smart contracts, and test scripts. Uses Hardhat, supports Solidity and TypeScript, and includes useful tools and tutorials for rapid onboarding.
3.3 Frontend Dependencies
To reduce workload and improve code quality, consider these recommended frontend libraries:
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wagmi: Provides rich React hooks for seamless contract interaction, simplifying transaction handling and contract calls.
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useDApp: Advanced React hooks library supporting multicall.js, enabling batch contract calls, ETH transfers, and EIP-712 signature handling.
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Siwe: Library for implementing secure wallet login workflows, easily integrable with other tools.
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i18next and react-i18next: Enable multilingual support, allowing easy language switching and management in the frontend.
4 Middleware Development
In DApp development, middleware sits between the frontend and blockchain network, acting as an intermediary layer managing blockchain interactions.
4.1 Middleware Functions
Middleware can perform the following:
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Wallet connection and authorization management: Handles wallet linking, login/logout, and manages user authentication and permissions.
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Transaction processing and signing: Manages contract interactions, constructs transactions, signs them, and broadcasts to the network. Handles transaction lifecycle including status updates and event listening.
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Data caching and querying: Caches contract data (e.g., view function results) to improve performance and responsiveness, refreshing as needed.
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Event listening and handling: Subscribes to blockchain events, parses them, and triggers appropriate actions, updating frontend state and UI accordingly.
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Error handling and logging: Captures and processes errors during blockchain interaction, providing meaningful feedback and logging for debugging.
4.2 Middleware Tools
Common middleware tools include:
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Web3.js: JavaScript library for Ethereum interaction—connects to network, instantiates contracts, sends transactions, reads data.
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ethers.js: Popular alternative to Web3.js with similar functionality—network connection, contract instantiation, transaction signing.
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Metamask: Widely used Ethereum wallet plugin integrating with Web3.js or ethers.js for wallet connection and transaction signing.
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Drizzle: Web3.js-based state management library designed for DApps. Manages app state, contract interaction, auto-subscribes to events, and auto-updates state.
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Truffle Suite: Development toolkit including Truffle (contract compilation/deployment/testing), Ganache (local blockchain), and Drizzle (state management).
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Infura: Node hosting service enabling easy Ethereum network access via API without running your own node.
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IPFS: Distributed file system for storing and retrieving large files or data in a decentralized, highly available manner—ideal for DApps requiring off-chain storage.
4.3 Security Considerations
Security must be prioritized when interacting with wallets and contracts. Use trusted connectors, validate wallet addresses and transaction status, perform input validation and data encryption, and conduct regular security reviews and patching.
Wallet connection security:
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Use trusted wallet connectors: Only use verified, reputable connectors like MetaMask, WalletConnect, or Portis.
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Limit user authorization: Ensure users understand which permissions they grant. Request only necessary permissions.
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Validate wallet addresses: Confirm user-provided addresses match the connected wallet using connector APIs.
Security for contract write operations:
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Transaction confirmation and signing: Require wallet confirmation and signing before executing writes, ensuring user authorization and added security.
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Input validation: Always validate user inputs before passing to contracts. Ensure data conforms to expected format and range to prevent malicious payloads.
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Monitor transaction status: Listen for transaction confirmations to ensure successful blockchain inclusion, then update frontend state and notify users.
Security for wallet login and signing:
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Use wallet-native signing: For sensitive operations (e.g., login), use wallet-provided signing instead of sending raw data to contracts. This keeps private keys secure and encrypts data locally.
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Data encryption: Apply proper encryption algorithms and protocols to protect sensitive data confidentiality during transmission.
Security review and vulnerability patching:
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Conduct security audits: Regularly audit code and architecture against best practices, identifying and fixing potential vulnerabilities.
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Patch vulnerabilities: Promptly fix and deploy updates upon discovering or receiving vulnerability reports. Timely response is critical for maintaining security.
5 Smart Contract Deployment
Contract deployment means publishing a smart contract onto the blockchain for execution and use.
5.1 Considerations
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Smart contract bytecode: Generated by compiling source code, bytecode is the executable machine code deployed on-chain. Represented as a hex string, it contains the contract’s logic and is central to on-chain execution.
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Gas: Every Ethereum transaction requires gas. Deploying a contract consumes gas proportional to its size and complexity, plus network congestion. Set a sufficient gas limit to ensure successful deployment.
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Deployment script or plugin: Automate deployment using scripts or plugins integrated into development tools. These reduce manual effort and minimize errors.
5.2 Tools for Deploying Smart Contracts
You can deploy smart contracts using the following tools:
Remix: An integrated development environment for developing, deploying, and managing Ethereum smart contracts. Use Remix to compile, debug, and deploy contracts via its UI. Official links:
Tenderly: A Web3 development platform offering debugging, observability, and infrastructure tools for developing, testing, monitoring, and operating smart contracts. Learn more:
Hardhat: A development environment for compiling, deploying, testing, and debugging Ethereum software. Write deployment scripts and execute them. Links:
Truffle: A development environment, testing framework, and deployment pipeline for Ethereum smart contracts. Write and run deployment scripts. Links:
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