A10: Blockchain Identity Lab★★☆ Medium

Assignment Type: Practical Lab (Take-Home or In-Class)
Time Allocation: 90 minutes
Points: 50 (40 core + 10 bonus)
Group Size: Individual

Learning Objectives

By completing this lab, you will:

Understand how arbitrary data is stored on a public blockchain
Use MetaMask to send transactions with custom data payloads
Experience content-addressed storage via IPFS
Verify on-chain data using a block explorer (Etherscan)
(Bonus) Understand NFT minting as a mechanism for on-chain media references

Learning Prerequisites

Before starting this lab, review the following lecture material:

Lesson 8: Regulation & Future Trends — Decentralized Identity (DID/SSI) and Soulbound Tokens (SBTs) slides

These slides cover the W3C DID standard, verifiable credentials, and soulbound tokens that form the theoretical foundation for this hands-on lab.

Technical Prerequisites

Computer with Chrome, Firefox, or Brave
MetaMask browser extension installed
Internet connection
A selfie or photo (any image file, under 5 MB)

Important: This lab uses the Sepolia TESTNET. No real money is involved. Testnet ETH has zero monetary value. All transactions are public and permanent on the testnet.

Phase 1: Wallet Setup & Testnet ETH (15 minutes)

1Install MetaMask

Go to https://metamask.io/download/
Add the extension to your browser
Create a new wallet and save your recovery phrase in a safe place

2Add Sepolia Testnet

Click the network dropdown in MetaMask (top-left)
Toggle "Show test networks" ON (Settings > Advanced)
Select "Sepolia test network"

3Get Free Testnet ETH

Visit any of the following faucets to request free Sepolia ETH:

Primary: Google Cloud Faucet
Alt 1: Chainlink Faucet
Alt 2: QuickNode Faucet
Alt 3: Alchemy Faucet (requires GitHub login)
Alt 4: Chainstack Faucet (0.5 ETH/day)

Paste your MetaMask wallet address into the faucet, request ETH, and wait 30–60 seconds. Confirm the balance appears in MetaMask.

Deliverable: Screenshot of MetaMask showing your Sepolia ETH balance.

Phase 2: Add Your Name to the Blockchain (20 minutes)

1Enable Hex Data in MetaMask

Open MetaMask > Settings (gear icon) > Advanced
Toggle ON "Show hex data"

Note: In MetaMask v11 and later, the "Show hex data" toggle may have been moved or renamed. If you do not see it under Settings > Advanced, look for a "Hex" tab directly in the Send transaction screen, or consult the MetaMask documentation for your version.

2Convert Your Name to Hex

Go to https://www.rapidtables.com/convert/number/ascii-to-hex.html
Type your full name (e.g., Alice Johnson - Cryptoeconomics 2026)
Copy the hex output
Prepend 0x to the hex string (e.g., 0x416C696365...)

3Send the Transaction

In MetaMask, click "Send"
Recipient: your own wallet address (send to yourself)
Amount: 0 ETH
Paste the hex string into the "Hex Data" field
Click "Next", review the gas fee (~0.0001 ETH on testnet)
Click "Confirm"

4Verify on Etherscan

Click the transaction in MetaMask > "View on block explorer"
Or go to https://sepolia.etherscan.io/ and search for your address
Find your transaction and click on it
Scroll to "Input Data"
Click "View Input As" > "UTF-8"
Your name should appear in plaintext!

Deliverable: Etherscan link showing your name in the transaction input data.

Phase 3: Add Your Picture to the Blockchain (30 minutes)

1Upload Image to IPFS via Pinata

Go to https://app.pinata.cloud/ and create a free account
Click "Add Files" > "File"
Upload your photo (selfie, portrait, any image under 5 MB)
Wait for the upload to complete
Copy the CID (Content Identifier) — it looks like QmX... or bafy...

2Find Your Dedicated Gateway URL

In your Pinata dashboard, go to "Gateways"
Note your account-specific gateway URL (format: your-gateway.mypinata.cloud)
Test your image: https://your-gateway.mypinata.cloud/ipfs/YOUR_CID

Important: The old public gateway (gateway.pinata.cloud) no longer works for new accounts. You must use your own dedicated gateway URL.

Understanding What Just Happened

IPFS = InterPlanetary File System (decentralized storage)
CID = cryptographic hash of the file content (content-addressed)
The same file always produces the same CID (deterministic)
Anyone with the CID can retrieve the file from IPFS
The image is not on the blockchain yet — only on IPFS

3Store the IPFS CID on the Blockchain

Convert the CID to hex using the same tool as Phase 2
Optionally prepend a label before converting: IPFS_CID:QmX...
Send another 0 ETH transaction to yourself with the hex CID in the data field
Confirm on Etherscan: the CID is now permanently on-chain

4Verify the Link

Take the CID from Etherscan (Input Data > UTF-8)
View the image via your Pinata gateway: https://your-gateway.mypinata.cloud/ipfs/YOUR_CID
The blockchain transaction proves you uploaded this specific image at this specific time

Deliverables:

Pinata dashboard screenshot showing the uploaded image with its CID
Etherscan link showing the CID in the transaction input data
Working IPFS gateway link to your image (using your dedicated gateway)

Phase 4 (Bonus): Mint Your Photo as an NFT (25 minutes)

1Go to thirdweb Dashboard

Visit https://thirdweb.com/dashboard
Connect MetaMask (ensure Sepolia network is selected)

2Deploy an NFT Contract

Click "Deploy" > browse contracts > "NFT Collection" (ERC-721)
Name: YourName Identity NFT
Symbol: IDNFT
Network: Sepolia
Click "Deploy Now"
Confirm the transaction(s) in MetaMask

3Mint Your NFT

Go to the "NFTs" tab in your deployed contract
Click "+ Mint"
Name: My Blockchain Identity - YourName
Description: My photo permanently linked to the blockchain
Image: upload your photo
Click "Mint NFT"
Confirm in MetaMask

4View Your NFT

Copy the contract address from thirdweb
Go to https://testnets.opensea.io/
Search for your contract address or connect your wallet
Your NFT should appear with your photo