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# System prepended metadata

title: '**Introduction to Blockchain:**'

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# **Introduction to Blockchain:**
**My Journey as a Beginner to Blockchain Programming**

![Screenshot from 2025-07-12 00-14-39](https://hackmd.io/_uploads/BJIljf1Uxx.png)


Week 2 of the Blockfuse Labs Web3 Education Cohort felt like stepping into a completely new dimension. Until now, blockchain had been one of those tech buzzwords I've heard floating around—mostly tied to Bitcoin, crypto, or NFTs. But this week, it finally clicked. I started to understand not just what blockchain is, but how it works under the hood and why it’s so important. We were introduced to Ethereum, decentralized networks, cryptography, and all the pieces that make this technology tick.
this was a mind blowing experience of learning and unlearning misconception of the blockchain network.

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### **So, What is Blockchain?**

We kicked things off with the basics. At its core, a blockchain is just a type of database—but it’s very different from the traditional ones most apps use. Instead of being controlled by one central authority, a blockchain is **decentralized**, meaning it lives across many computers (called nodes) on a peer-to-peer network. Everyone sees the same data, and no one can secretly change anything.

Each block contains 
1. A group of transactions, 
2. A timestamp, 
3. and something called a **hash**—a kind of digital fingerprint. 

Every block also references the hash of the block before it, which links them together. That’s the “chain” part. If you change anything in a block, its hash changes, and that breaks the chain. This is what makes the data **immutable**—it can’t be tampered with without affecting everything after it.

We also experimented on this concept in the andersbrownworth blockchain sandbox(https://andersbrownworth.com/blockchain/blockchain)

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### **Nodes, Broadcasting, and Network Structure**

The blockchain network is made up of nodes—computers that store a full copy of the blockchain. When someone initiates a transaction, it’s broadcast to the network. Each node checks the transaction for validity, and once it passes, it can be added to a block. This system is very resilient because there’s no single point of failure. Unlike traditional servers, it’s difficult to target and shut down all nodes.

This also makes the network resistant to **Denial of Service (DoS)** and **Distributed Denial of Service (DDoS)** attacks, which usually rely on overwhelming a centralized server. In a blockchain, every node shares the responsibility, so there's no single server to attack.

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### **Hashing and Security**

One of the biggest things keeping blockchain secure is **cryptographic hashing**. All data on the blockchain was added to the blockchain forms a permanent part of the network and cannot be tempered with. Even the smallest change in input data completely changes the hash. This property ensures that no one can quietly modify data without being noticed.
Hashing ensures that the state of the network is always in sync and any change made to any block on the network automatically invalidates the preceeding nodes and would therefore require that all nodes reach an agreement to validate the block and correct its hash and preceeding hashes. This adds a layer if security to the network that makes it temper-proof

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### **Consensus: Proof of Work vs Proof of Stake**

Consensus is simply an agreement reached by all the nodes to the truth of the current state of the network. It is a set of principles and rules that a blockchain network uses to reach an agreement on the current state of the network.

Ethereum recently moved from **Proof of Work (PoW)** to **Proof of Stake (PoS)** consensus mechanism. PoW required miners to solve complex puzzles using huge amounts of energy just to propose new blocks and compete for the first to complete this puzzel based on the competence of its processing power. PoS is way more efficient.

In PoS, validators are chosen to propose and attest blocks based on how much ETH they’re willing to lock up as a **stake**. If a validator acts dishonestly, their stake can be **slashed**—which means they lose part of it. This setup encourages validators to behave honestly and helps the network stay secure and energy-efficient.

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### **Understanding Ether and Gas**

We learned that **Ether (ETH)** is different from Ethereum. Ethereum is the network, powered by the EVM while Eth is the native cryptocurrency of Ethereum. But it’s not just for payments—it powers the entire network. Every transaction and smart contract interaction costs **gas**, which is paid in ETH. Gas is a measure of computational work, and the more complex an operation, the more gas it requires.

ETH also has smaller units or denominations:

* **Wei** – the smallest unit (1 ETH = 10¹⁸ wei)
* **Gwei** – commonly used for gas fees (1 Gwei = 10⁹ wei)
* Other denominations include Kwei, Mwei, Finney, Szabo, etc.


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### **Ethereum Accounts: EOAs vs Contract Accounts**

Ethereum has two types of accounts:

1. **Externally Owned Accounts (EOAs)** – controlled by users through a private key. They can initiate transactions and interact with contracts.
2. **Contract Accounts** – controlled by deployed smart contracts. They can hold ETH and run code but can’t initiate transactions themselves.

Each Ethereum account has these components:

* **Nonce** – number of transactions sent (used to prevent replay attacks)
* **Balance** – amount of ETH it holds
* **Code Hash** – if it's a contract account, this stores the code while for EOAs, this is an empty string.
* **Storage Root** – stores state data for smart contracts

Only one transaction can be sent with a given nonce. Reusing it will fail, which helps maintain transaction order and uniqueness and also prevents replay attack, where a user can rebroadcast the same transaction over and over again.

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### **Smart Contracts and DApps**

We learned that **Smart contracts** are like code stored on the blockchain. Once deployed, they can’t be changed, which makes them trustworthy but also hard to maintain. If you make a mistake in your smart contract, you have to deploy a whole new version. However, we were hinted about a concept called upgradable smart contracts which we would come across as we continue to learn about the blockchain.

**DApps (Decentralized Applications)** are basically application built/deployed on a decentralized network. Dapps are a combination of smart contracts (the backend) and a regular frontend for users. They run on the blockchain, not centralized servers, which means they’re harder to censor or take down—but also come with challenges like expensive gas fees and limited scalability.

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### **The Blockchain Trilemma**

One concept that stuck with me was the **blockchain trilemma**. the blockchian is built on 3 pillars:

* **Security**
* **Scalability**
* **Decentralization**

the trilemma problem says you can’t have all three of these at once, solving 2 of these problems leads to the sacrifice of the third.

Most blockchains pick two and compromise on the third. Ethereum, for example, is highly secure and decentralized but struggles with scalability. That’s why gas fees can spike and transaction speeds can lag.

However, to solve these problems, one key concept it to use a modular setup where networks (also known as layer1 networks) focus their resources on 2 of the three problems and collaborate with other networks (also known as layer2 networks) to solve the third. together, these network ultimately solve the trilemma problem

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### **Web Evolution: From Web1 to Web3**

We also explored how the internet has evolved:

* **Web1**: Read-only. Just basic web pages with no interactivity.
* **Web2**: Read and write. Social media, blogs, cloud services—but everything is owned by big tech companies.
* **Web3**: Read, write, and *own*. Users own their data, identity, and assets. It’s built on blockchain and is still developing.

Web3 promises a more open and user-controlled web, but it needs better UX and more scalability before it becomes mainstream.

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### **Limitations and Challenges of Web3**

Web3 introduces a lot of exciting possibilities, but it’s not perfect. It can be:

Hard to use: Wallets, private keys, seed phrases—it’s a lot for beginners.

Expensive: Gas fees can be unpredictable and high.

Slow: Transactions can take time to process.

Hard to update: Because contracts are immutable, fixing bugs isn’t straightforward.

Still, these limitations are just growing pains. Every new wave of technology starts rough around the edges. Developers, researchers, and open-source contributors all over the world are actively working to solve these problems through better tools, infrastructure upgrades, and more intuitive interfaces. As innovation continues, the barriers will get lower and adoption will increase.

The promise of Web3 is too powerful to ignore—a web where users own their identity, data, and assets, and where the control shifts from corporations to communities. With time, education, and better engineering, the future of Web3 shines bright.

### **Conclusion**

Week 2 opened my eyes to how much depth the blockchain world really holds. I now see it as more than crypto and buzz—it’s infrastructure for a new kind of internet. Sure, Web3 has its flaws, but that’s how innovation starts: messy, promising, and full of potential.

I'm still early in this journey, but I can already feel how big this can get. With every new thing I learn, I feel more prepared to play my part in shaping the future of decentralized technology.

**Excited about what week3 holds** --The journey is just beginning.

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📌 Also, check out my very first technical article where I explore fundamental engineering concepts like latency, scaling, roundtrip time, throughput, and distributed systems: https://hackmd.io/@SNM3LLvKTRmNV78cmblX5A/Bk5PM7JLle


