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Blockchain — Technology & Smart Contract Development

Last reviewed: 2026-09-17

Blockchain is a distributed ledger technology that records transactions across a network of computers in an immutable, transparent, and decentralized manner. Beyond cryptocurrencies, blockchain enables smart contracts, DeFi, NFTs, supply chain tracking, and decentralized applications (dApps).

Overview

A blockchain consists of a chain of blocks, each containing: - Transactions — Data being recorded - Timestamp — When the block was created - Previous block hash — Links blocks together (immutability) - Nonce — Proof-of-Work / consensus mechanism - Merkle root — Hash of all transactions in the block

Topics Covered

  • Solidity programming — language basics, contract structure, state, functions
  • Token standards — the ERC-20 fungible-token standard and how it is implemented
  • Hardhat — local development environment, compilation, scripts
  • Smart contract testing — unit tests against a local chain
  • Testnet deployment — Goerli / Sepolia deployment workflow
  • Frontend integration — Web3.js / Ethers.js clients against a deployed contract

Key Concepts

Consensus Mechanisms

Mechanism Description Used By
Proof of Work (PoW) Miners solve computational puzzles Bitcoin (legacy)
Proof of Stake (PoS) Validators stake tokens as collateral Ethereum, Solana
Delegated PoS (DPoS) Token holders vote for delegates EOS, TRON
Proof of Authority (PoA) Pre-approved validators Private/permissioned chains
Proof of History (PoH) Timestamp-based sequencing Solana

Smart Contracts

Self-executing contracts with terms written in code:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract SimpleStorage {
    uint256 private value;

    function set(uint256 _value) public {
        value = _value;
    }

    function get() public view returns (uint256) {
        return value;
    }
}

Token Standards (Ethereum)

Standard Purpose Example
ERC-20 Fungible tokens (currency) USDC, UNI
ERC-721 Non-fungible tokens (NFTs) Bored Ape Yacht Club
ERC-1155 Multi-token (fungible + non-fungible) Gaming items
ERC-4626 Tokenized vaults Yield-bearing tokens

Development Stack

Layer Tool/Framework
Smart Contract Solidity, Vyper
Development Hardhat, Foundry, Truffle
Testing Hardhat tests, Waffle, Chai
Frontend Ethers.js, Web3.js, wagmi, Rainbow Kit
Wallet MetaMask, WalletConnect, Coinbase Wallet
Indexing The Graph (subgraphs)
Storage IPFS, Arweave, Filecoin
Oracles Chainlink, Pyth
Network Type Gas Token
Ethereum L1 (mainnet) ETH
Polygon L2 sidechain MATIC
Arbitrum L2 optimistic rollup ETH
Optimism L2 optimistic rollup ETH
Base L2 (Coinbase) ETH
Solana L1 (PoH + PoS) SOL
Avalanche L1 (subnets) AVAX

Getting Started

  1. Install MetaMask browser extension
  2. Fund a wallet (testnet ETH from faucet)
  3. Write a simple Solidity contract in Remix IDE
  4. Deploy to a test network (Sepolia)
  5. Build a frontend with Ethers.js + React
  6. Explore Hardhat for local development and testing

Resources

To-do

Status: incomplete. Still to write:

  • Write the Solidity teaching content promised under 'Solidity programming' (language basics, contract structure, state, functions, visibility) — the article shows only a 10-line SimpleStorage sample.
  • Write the ERC-20 implementation promised under Token standards — currently a single table row with no contract code.
  • Write the Hardhat section promised in Topics Covered (local environment, compilation, scripts).
  • Write the smart contract testing section promised in Topics Covered (unit tests against a local chain).
  • Write the testnet deployment workflow (Sepolia) and the Web3.js/Ethers.js frontend integration — both appear only as one-line steps in 'Getting Started'.