📘 LAB 1: Foundations of Blockchain – Simulating a Chain & Deploying an Immutable Poll

Duration: 1 hour
Difficulty: Beginner
Alignment: Course Objectives 1 & 6 (Understand blockchain principles; Build a basic prototype/dApp)
Prerequisites: Basic Python knowledge, ability to install browser extensions, internet connection

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📁 Files Provided

File 1: simple_blockchain.py

File 2: SimplePol.sol

🧭 Step-by-Step Lab Guidelines

🔧 PART A: Simulate Blockchain Fundamentals (Python)

1. Install Python (if not installed): https://python.org/downloads
2. Run the simulation:

   python simple_blockchain.py

3. Observe Output:
   • Note how each block's hash depends on previous_hash
   • Notice the is_valid() function returns False after tampering
4. Experiment:
   • Change bc.add_block("Vote: YES") to your name + a short message
   • Re-run and observe how the hash chain updates automatically
5. Concept Check:
   • Why does changing one block break the chain?
   • How does this relate to immutability in real blockchains?

🌐 PART B: Deploy & Interact on a Live Testnet (Remix + MetaMask)

1. Install MetaMask: https://metamask.io/download/
   • Create a wallet (save recovery phrase securely)
   • Switch network to Sepolia Testnet
2. Get Test ETH:
   • Visit: https://sepoliafaucet.com/ or https://faucets.chain.link/sepolia
   • Paste your MetaMask address and request free test ETH
3. Open Remix IDE: https://remix.ethereum.org/
   • Create a new file: SimplePoll.sol
   • Paste the Solidity code provided above
   • Click Solidity Compiler → Select 0.8.20 (or compatible) → Click Compile
4. Deploy:
   • Go to Deploy & Run Transactions
   • Environment: Select Injected Provider - MetaMask
   • Confirm connection in MetaMask
   • Click Deploy → Approve transaction in MetaMask
5. Interact:
   • In the deployed contract panel, expand createPoll
   • Input: _question: "Should we adopt blockchain in our campus?"
   • _options: ["Yes", "No"] → Click transact
   • Wait for confirmation (~15 secs)
   • Expand vote → Input _pollId: 0, _optionIndex: 0 → Click transact
   • Repeat vote with index 1
   • Expand getPoll → Input 0 → Click call to view results
6. Verify on Etherscan:
   • Copy contract address from Remix
   • Paste into: https://sepolia.etherscan.io/
   • View transaction hashes, events, and gas usage

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🛠️ Troubleshooting Guide

Issue	Solution
pip install errors	Use Python 3.10+. No external packages required for this lab.
MetaMask not connecting to Remix	Ensure MetaMask is unlocked & set to Sepolia. Refresh Remix after switching networks.
"Out of gas" on deployment	Request more test ETH from faucet. Set gas limit to 300000 in Remix advanced settings.
getPoll returns empty	Wait for transaction confirmation (15–30s). Check Etherscan for pending status.
Solidity compiler mismatch	In Remix Compiler tab, select 0.8.0 or higher. Code uses pragma solidity ^0.8.0;

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🔗 Week 1 Tool Integration Map

Lab Component	Course Tool Used	Concept Demonstrated
simple_blockchain.py	Python hashlib	Hash functions, block linking, immutability
SimplePoll.sol + Remix	Remix IDE, Solidity	Smart contract structure, on-chain execution
MetaMask + Sepolia	MetaMask, Testnet	Wallets, gas, transaction signing, public ledger
Etherscan Verification	Blockchain Explorer	Transparency, auditability, real-time verification

💡 Note: This lab intentionally avoids complex frontend frameworks or advanced Solidity patterns. It focuses on experiential learning: students first simulate blockchain mechanics locally, then interact with a live decentralized network. This bridges Week 1 theory with the hands-on development covered in Weeks 5–7.