Blockchain Development Tutorial #2: Ethereum Public Chain - How to Develop Your Own Blockchain

Introduction

This technical tutorial explores Ethereum, the pioneer of blockchain 2.0 and smart contracts. For foundational concepts, refer to this tutorial.

Key Ethereum Features:

• Supports smart contracts via the Ethereum Virtual Machine (EVM).
• Uses an account-balance model (not UTXO like Bitcoin).
• Launched in 2015 by Vitalik Buterin, employing PoW consensus (~13–15 sec/block).

1. Ethereum Accounts

Ethereum accounts are categorized into:

• Externally Owned Accounts (EOAs): Controlled by private keys (user wallets).
• Contract Accounts: Hold smart contract code, lacking private keys.

Address Generation

Ethereum addresses derive from Keccak-256 hashes of uncompressed public keys (secp256k1 curve). The last 20 bytes prefix with 0x form the address.

Code Example:

const randomBytes = require('randombytes');
const ethUtil = require('ethereumjs-util');
let priKey = randomBytes(32).toString('hex');
let pubKey = ethUtil.privateToPublic(new Buffer(priKey, 'hex')).toString('hex');
let addr = ethUtil.pubToAddress(new Buffer(pubKey, 'hex')).toString('hex');

EIP-55 Checksum:
Addresses can include uppercase letters for checksum validation (e.g., 0xAa...). This prevents typos but remains backward-compatible.

2. Smart Contracts

Example: Voting Contract

pragma solidity ^0.8.0;
contract Vote {
    event Voted(address indexed voter, uint8 proposal);
    mapping(address => bool) public voted;
    uint256 public endTime;
    uint256 public proposalA;
    // ... (additional proposals)
    
    constructor(uint256 _endTime) { endTime = _endTime; }
    
    function vote(uint8 _proposal) public {
        require(block.timestamp < endTime, "Voting closed.");
        require(!voted[msg.sender], "Already voted.");
        voted[msg.sender] = true;
        if (_proposal == 1) proposalA++;
        // ... (handle other proposals)
        emit Voted(msg.sender, _proposal);
    }
    
    function votes() public view returns (uint256) {
        return proposalA + proposalB + proposalC;
    }
}

Key Points:

• view functions read data without gas costs.
• Write functions (e.g., vote()) modify state and consume gas.
• Events (e.g., Voted) log actions for off-chain monitoring.

3. Deploying Contracts

Steps:

1. Testnet Setup: Use Ropsten and acquire test ETH from faucets.

2. Tools:

   • Remix IDE: Browser-based deployment.
   • Truffle: Automated deployment via scripts.

4. Building a DApp

Architecture:

1. Frontend: Connects to MetaMask via ethers.js.
2. Backend (Optional): Aggregates contract data for non-wallet users.

Frontend Code Snippet:

const VOTE_ADDR = '0x5b2a057e1db47463695b4629114cbdae99235a46';
const VOTE_ABI = [...]; // From Remix JSON

async function vote(proposal) {
    const contract = new ethers.Contract(VOTE_ADDR, VOTE_ABI, window.ethereum);
    const tx = await contract.vote(proposal);
    await tx.wait(1); // Wait for confirmation
}

Backend Best Practices:

• Cache contract data.
• Listen to events via eth_getLogs.

FAQs

Q1: Can contract and user addresses collide?

No. Both derive from the same hashing method, but contracts lack private keys. Transactions to contracts trigger their fallback function.

Q2: How to verify an address?

Use checksum (EIP-55) or libraries like ethers.utils.getAddress().

Q3: Why use a backend server?

To serve data when users lack wallet connectivity or need historical analytics.

References

1. Ethereum Foundation
2. Solidity Docs

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