Forem: Hemapriya Kanagala

How I Built a Blockchain User Profile with Solidity (and You Can Too)

Hemapriya Kanagala — Tue, 29 Jul 2025 03:57:11 +0000

This is a smart contract I wrote using Solidity that lets people register and update their profile on the blockchain. It was one of the first contracts I built to understand how user data works on Ethereum.

The idea is simple:

Everyone has a wallet address. What if we could let each address store their name, age, and email - all saved on-chain?

So I built that.

Here is the GitHub link if you want to check out the code.

I wrote just one file: UserProfile.sol.

What This Contract Does

This smart contract lets a user:

Register their name, age, and email
Update that information later
View their own profile (no one else can access it)

Everything is connected to their Ethereum wallet address, so you don’t need to log in - your wallet is your ID.

Concepts I Used

If you're new to Solidity or smart contracts, these are the main building blocks I used:

Concept	What It Does
`struct`	Groups related data - like name, age, and email - into a single object
`mapping`	Stores info for each user using their wallet address as the key
`require()`	Adds checks so people don’t register twice or update before registering
`block.timestamp`	Saves the time a user registered, using the blockchain’s clock

Each time someone registers, their info is stored on the blockchain - and only they can update or view it.

How It Works

Here’s what the contract does in plain English:

1. `register(name, age, email)`

This function saves your profile to the blockchain - but only if you haven’t registered before. If you try again, it gives an error.

2. `updateProfile(name, age, email)`

If you already registered, this lets you change your info anytime.

3. `getProfile()`

This function shows your current profile - your name, age, email, and the time you first registered. Only you can see it (based on your wallet).

How to Try It Yourself (Beginner-Friendly)

You don’t need a real wallet or ETH to test this. Remix IDE runs everything in your browser using fake ETH.

Steps to Test the User Profile Contract

Go to Remix

→ https://remix.ethereum.org
Create a new file

→ Click “+” → Name it UserProfile.sol
Paste in the contract code

→ You can find it here on GitHub
Compile it

→ Go to the Solidity Compiler tab

→ Make sure version is 0.8.0 or higher

→ Click Compile
Deploy it

→ Go to the Deploy & Run Transactions tab

→ Select Remix VM (Prague) as environment

→ Leave Value as 0

→ Click Deploy
Register yourself

→ Fill in name, age, and email

→ Click register()

✅ You’ll see a green checkmark
Check your profile

→ Click getProfile()

✅ Your info will appear: name, age, email, and timestamp
Try updating it

→ Enter new name, age, or email

→ Click updateProfile()

→ Then click getProfile() again to see the updated info

What I Learned

Lesson	How I Used It
Structs in Solidity	Grouped user info like name, age, email
Mappings	Stored each user's profile by their address
Access control with `msg.sender`	Made sure only the owner of a profile can update or view it
Blockchain timestamp	Recorded when each user registered
Remix testing	Quickly deployed and tested without real ETH

Common Mistakes to Avoid

Mistake	Why It’s a Problem	How I Solved It
Registering twice	Contract would overwrite data	Used `require()` to block double registration
Updating before registering	User wouldn’t exist in mapping yet	Added `require()` to check registration first
Returning too much data	Could make `view` functions heavy	Kept `getProfile()` simple and clear

Up Next

I’d really appreciate your questions or feedback. Did something confuse you? Let me know. Your insights help shape the next articles.

Also, if there’s a non-Web3 topic you want me to cover (open source, side projects, etc), drop a comment below. If I know it, I’ll write about it. If not, I’ll point you to a good place to begin.

🤝 Stay in Touch

Check out the GitHub repo
Follow me on GitHub for projects and experiments
Connect with me on LinkedIn - I’d love to hear from you
Drop a comment if you tried this or have questions - I’d love to help!

Thanks for reading!

What Actually Happens When You Make a Blockchain Transaction?

Hemapriya Kanagala — Fri, 25 Jul 2025 06:33:31 +0000

Welcome back! If you read Article 1: A Beginner’s Guide to How Blockchain Actually Works, we walked through what a blockchain is, how blocks form, and why decentralization matters.

Now let’s get a little more hands-on.

You’ve probably heard things like:

“Just send me crypto.”

“It’s on the blockchain.”

“Check your wallet.”

But what does that actually mean? What happens under the hood when you send a transaction?

This article takes you behind the scenes - from clicking “Send” in your wallet to seeing the transaction confirmed on a blockchain explorer.

Step-by-Step: How a Blockchain Transaction Works

Let’s follow a single transaction from start to finish. We’ll use a simple example:

You want to send 1 token to a friend using a wallet like MetaMask.

Here’s what happens behind the scenes:

1. You Create the Transaction in Your Wallet

A wallet is an interface that lets you interact with the blockchain. It stores your private key (securely) and helps you sign transactions.

You enter:

Your friend’s public address
Amount to send
Optional message or data (depends on blockchain)
The gas fee you're willing to pay

Your wallet then signs the transaction using your private key. This proves it came from you, without ever revealing your key.

📌 Signing means creating a unique digital signature based on your private key and the transaction data.

2. Your Wallet Broadcasts the Transaction to the Network

Once signed, the transaction is broadcast to the network. This means it’s sent to nearby nodes (computers running the blockchain software).

Those nodes check if:

Your signature is valid
You have enough balance
The transaction is formatted correctly

If it looks good, they pass it on to more nodes - spreading it across the network, like sharing a file with everyone.

📌 Nodes are participants in the blockchain network. They validate transactions and keep a full copy of the blockchain.

3. The Transaction Enters the Mempool

Valid transactions are stored in something called the mempool - short for memory pool. Think of it as a waiting room where pending transactions sit before being added to a block.

Every node maintains its own mempool, but they’re usually very similar.

Inside the mempool:

Transactions are ranked (usually by fee amount)
Miners or validators pick from the top

📌 The mempool is like a “to-do list” for the network.

4. A Validator Picks It Up and Adds It to a Block

Depending on the blockchain’s consensus method, a participant is selected to propose the next block. This could be a miner (Proof of Work) or validator (Proof of Stake).

They:

Pick high-fee transactions from the mempool
Group them into a block
Validate and order them
Propose the block to the network

If accepted, the block is added to the chain - and your transaction is officially recorded.

📌 A block contains many transactions, plus metadata like timestamp, block number, and a hash of the previous block.

5. You See the Transaction Confirmed

Once included in a block, your transaction gets a confirmation.

Over time, more blocks are added after it - which makes your transaction harder to reverse. That’s why you’ll hear things like:

“Wait for 3 confirmations.”

“It’s confirmed on-chain.”

You (or anyone) can view it on a blockchain explorer like LiskScan or Etherscan. These tools let you search by:

Wallet address
Transaction hash
Block number

A Real-World Analogy: Certified Mail

Here’s a way to picture the entire process using something familiar — mailing a certified letter.

Blockchain Step	Certified Mail Equivalent
Create transaction in wallet	Write a letter, sign the envelope
Broadcast to network	Drop it at your local post office
Mempool	Letter goes into a mail sorting facility
Validator adds it to block	A courier picks it up and delivers it
Confirmed on-chain	Recipient signs for it, and delivery is logged

Both systems involve signing, routing, validation, and a final delivery record.

Wait... What’s This “Gas Fee” I’m Paying?

On most blockchains, every transaction requires a small payment - called a gas fee.

You’re paying the network to:

Validate your transaction
Store it in a block
Broadcast it across the chain

Fees vary based on:

Network congestion (how full the mempool is)
Complexity of your transaction (simple send vs smart contract)
Priority (higher fee = faster confirmation)

On Ethereum, gas is measured in gwei. On Lisk, it’s based on LSK token units.

Here’s a quick comparison:

Transaction Type	Typical Gas Fee (Estimates)
Simple token transfer	Low
NFT mint or marketplace buy	Medium
Complex smart contract call	Higher (depends on logic & storage)

Tip: Always check the fee before sending - wallets like MetaMask show it clearly.

How Long Does It Take?

Transaction time depends on:

The blockchain’s block time (e.g. Ethereum ~12s, Lisk ~10s)
Network traffic
Your fee

Blockchain	Avg Block Time	Confirm Time (1 block)	Notes
Ethereum (PoS)	~12 sec	~12 sec	High usage = higher fees
Bitcoin (PoW)	~10 min	~10 min	Slower but more secure
Lisk (PoS)	~10 sec	~10 sec	Fast and energy-efficient

More confirmations = stronger finality (i.e. harder to reverse).

What If Two People Try to Send the Same Coins?

The blockchain uses the nonce (a number that increases with each transaction) to prevent double spending.

If someone tries to send the same coins twice, only the valid transaction with the correct nonce will be accepted. The rest will be ignored.

Why Transactions Sometimes Fail

Here are common reasons a transaction doesn’t go through:

Problem	Cause
“Out of gas” error	You didn’t pay enough to complete it
“Nonce too low”	Another transaction was already sent before this one
Stuck in mempool	Gas fee too low, not attractive to validators
Wrong network selected	You sent tokens on the wrong chain

Always double-check your settings before hitting Send.

Can I Try This Myself?

Yes, if you’re curious and want to see this in action, here’s a safe, free way to experiment using a test network.

Install MetaMask browser extension
Create a new wallet and save your secret phrase securely
Add Lisk Sepolia as a custom network
Get free test tokens from the L2 Faucet
Use MetaMask to send a small token to yourself
Go to LiskScan and look up your wallet address
See your transaction as it appears on-chain

This gives you a hands-on feel for how blockchain transactions work.

Or, if this still feels early, you can just keep learning. Later articles will help build your confidence.

What’s Next?

I’d really appreciate your questions or feedback. Did something confuse you? Let me know. Your insights help shape the next articles.

🤝 Stay in Touch

Follow me on GitHub for projects and experiments
Connect with me on LinkedIn - I’d love to hear from you
Drop a comment or message if something clicked or confused; I read all of them.

A Beginner’s Guide to How Blockchain Actually Works

Hemapriya Kanagala — Fri, 18 Jul 2025 22:44:47 +0000

If you've ever heard the word "blockchain" and thought, “Sounds complicated... probably not for me,” you're not alone. That was me too, not long ago. But the more I dug in, the more I realized it’s not some far-off concept meant only for coders or finance experts. It’s actually a simple idea that has the potential to change how we do things online, from sending money to keeping records and building apps.

What Is Blockchain?

Think of a digital notebook shared by many people at once. Every time someone records a transaction, it shows up instantly in everyone’s copy. No one can delete past entries or alter them without being noticed.

That unchangeable, transparent, shared structure is essentially what blockchain is. The participants all maintain it - no single person owns it. That’s what “decentralized” means.

Why Does It Matter?

Today, we depend on systems like banks, messaging platforms, or organizations to handle transactions, verify identities, or secure agreements. These intermediaries add layers of trust, fees, and delays.

Blockchain removes those layers by embedding trust in the system itself. People call it “trustless,” meaning you don’t have to rely on a central authority. The rules are enforced by the entire network.

How Blocks Form a Chain

A block is simply a collection of data - commonly a group of transactions. Inside each block you’ll find:

The details of what happened
A timestamp
A unique digital signature (called a hash)
A reference to the previous block’s hash

Linking blocks this way creates a chain. If someone tampers with a block, its hash changes and eventually the links break. That’s what makes the blockchain secure.

How the Network Decides What’s Real

Without a central authority, blockchains rely on a system called consensus. All participants (called nodes) follow a set of rules to verify transactions and add new blocks.

Here are two popular methods:

Proof of Work

Miners compete to solve a math problem. Whoever solves it adds the next block and earns a reward. This method secures the network but uses a lot of energy.

Proof of Stake

Participants lock up some of their coins as collateral. The network chooses one to add the next block. This method is faster and uses far less energy.

Most newer networks like Ethereum and Lisk use Proof of Stake today.

Public vs. Private Blockchains: What’s the Difference?

Some blockchains are open to anyone. Others are private and used within companies.

Feature	Public Blockchain	Private Blockchain
Who can use it?	Anyone	Only approved users
Who controls it?	No one	One organization
Examples	Bitcoin, Ethereum	Hyperledger, Corda

Public ones are like a public park. Anyone can enter and use it.

Private ones are more like an office building. You need a keycard.

Quick Pause: What About Security?

One word: cryptography.

Blockchains use strong math-based tools to keep things safe. Each user has two keys:

A public key, which is like your email address (you can share it)
A private key, which is like your password (you never share it)

Together, these keys help verify that transactions are real. If someone sends money, their private key is used to “sign” the transaction, proving it came from them.

Smart Contracts: Programs That Run Themselves

This part blew my mind the first time I understood it.

Smart contracts are self-executing agreements written in code. They live on the blockchain, and when conditions are met, they act on their own.

Example:

Let’s say you hire a freelancer online. Instead of using a middleman to hold the payment, you create a smart contract. When the work is marked as done, the money automatically goes to the freelancer.

No one can interfere. The contract is the boss.

Smart contracts are being used in:

DeFi (decentralized finance)
NFT marketplaces
Blockchain-based games
Digital voting

Challenges and Real Solutions

Blockchain sounds amazing, but it’s not perfect. Here are a few issues and how developers are solving them.

1. Scalability

Popular blockchains can get congested and slow.

Solution:

Use Layer 2 tools, like rollups, which process transactions more efficiently. Think of it like adding an express lane to a busy highway.

2. Energy Use

Proof of Work blockchains use a ton of power.

Solution:

Moving to Proof of Stake reduces energy use by over 90 percent. Ethereum already made this change.

3. Regulations

Governments are still figuring out how to handle crypto and blockchain legally.

Solution:

New laws are being written, and tools like Decentralized Identity (DID) are helping users stay compliant while protecting privacy.

What Is the Superchain?

Some projects, like those based on the OP Stack, aim to connect blockchains together so they can share updates and improvements. Lisk is part of this vision. The idea is a flexible, scalable, cooperative network of blockchains.

How to Begin Yourself

You don’t need coding skills to try it:

Install MetaMask
Create a wallet and save your recovery phrase
Add the Lisk Sepolia test network
Get free tokens from L2 Faucet
Send a token to yourself or a friend
See the transaction on a blockchain explorer

You’ve now used a blockchain.

Summary

Blockchain is a secure, shared digital record
It’s decentralized - no single owner
Blockchains use cryptography and consensus to stay honest
Smart contracts let you automate agreements
There are challenges, but active solutions exist
You can try blockchain yourself without cost

What Comes Next

In the next article, we’ll dive into what happens when you send a transaction - from your wallet all the way to confirmation on the blockchain.

I’d really appreciate your questions or feedback. Did something confuse you? Let me know. Your insights help shape the next articles.

🤝 Stay in Touch

Follow me on GitHub for projects and experiments
Connect with me on LinkedIn - I’d love to hear from you
Drop a comment or message if something clicked or confused; I read all of them.

See you in Article 2.

Forem: Hemapriya Kanagala

How I Built a Blockchain User Profile with Solidity (and You Can Too)

What This Contract Does

Concepts I Used

How It Works

1. register(name, age, email)

2. updateProfile(name, age, email)

3. getProfile()

How to Try It Yourself (Beginner-Friendly)

Steps to Test the User Profile Contract

What I Learned

Common Mistakes to Avoid

Up Next

🤝 Stay in Touch

What Actually Happens When You Make a Blockchain Transaction?

Step-by-Step: How a Blockchain Transaction Works

1. You Create the Transaction in Your Wallet

2. Your Wallet Broadcasts the Transaction to the Network

3. The Transaction Enters the Mempool

4. A Validator Picks It Up and Adds It to a Block

5. You See the Transaction Confirmed

A Real-World Analogy: Certified Mail

Wait... What’s This “Gas Fee” I’m Paying?

How Long Does It Take?

What If Two People Try to Send the Same Coins?

Why Transactions Sometimes Fail

Can I Try This Myself?

What’s Next?

🤝 Stay in Touch

A Beginner’s Guide to How Blockchain Actually Works

What Is Blockchain?

Why Does It Matter?

How Blocks Form a Chain

How the Network Decides What’s Real

Proof of Work

Proof of Stake

Public vs. Private Blockchains: What’s the Difference?

Quick Pause: What About Security?

Smart Contracts: Programs That Run Themselves

Challenges and Real Solutions

1. Scalability

2. Energy Use

3. Regulations

What Is the Superchain?

How to Begin Yourself

Summary

What Comes Next

🤝 Stay in Touch

1. `register(name, age, email)`

2. `updateProfile(name, age, email)`

3. `getProfile()`