This project demonstrates how to deploy and interact with a simple smart contract using Solidity, Ethers.js, Ganache for local development, and Alchemy for deploying to the Sepolia testnet.

• Solidity – to write the smart contract (SimpleStorage.sol)
• Ganache – a personal Ethereum blockchain for local development
• Ethers.js – a JavaScript library to interact with the Ethereum blockchain
• Node.js – to run JavaScript files outside the browser
• Alchemy – to connect to the Sepolia testnet
• dotenv – to manage environment variables securely

The project allows you to:

• Store a favorite number on the blockchain.
• Retrieve the stored number.
• Add a person with their name and favorite number.
• Map names to favorite numbers using a mapping.
• Deploy and interact with the contract using JavaScript, not just Remix.

You write a smart contract called SimpleStorage.sol. It:

• Lets users store and retrieve a number.
• Maps names to numbers using mapping.
• Keeps track of people added using a struct and an array.

Before deploying the contract, you must encrypt your wallet’s private key to protect it.

To do this:

node encryptKey.js

This script uses your raw private key and password (from .env) to generate a secure .encryptedKey.json file.

Why? 👉 Never store or upload raw private keys. Encryption adds a layer of safety.

Now that your key is encrypted, you can deploy the contract:

node Deploy.js

What happens in this script:

• Connects to Sepolia via Alchemy using your RPC URL.

• Decrypts your encrypted key.

• Reads the ABI and binary code from compiled contract files.

• Deploys the contract to the blockchain.

• Waits for the transaction to be mined (confirmed).

• Interacts with the contract:

  • Reads the default stored value.
  • Updates it with a new value.
  • Reads it again to confirm the change.