Blockchain Tutorial: Learn with Examples
Eliza Thornton
⚡ Smart Summary
Blockchain is a chain of cryptographically linked blocks that records transactions across a distributed peer-to-peer network, removing intermediaries while making the ledger transparent, tamper resistant, and verifiable for finance, supply chain, identity, and emerging artificial intelligence workloads.
What is Blockchain?
Blockchain is a chain of blocks that contains information. The technique is designed to timestamp digital documents so that nobody can backdate or tamper with them. Blockchain solves the double record problem without relying on a central server, which is why it underpins so much of the modern digital economy.
The blockchain is used for the secure transfer of items like money, property, and contracts, without requiring a third-party intermediary such as a bank or a government agency. Once data is recorded inside a blockchain, it becomes extremely difficult to change.
Blockchain is a software protocol similar to how SMTP works for email. However, blockchains cannot run without the internet, and they are sometimes called a meta technology because they influence other technologies. The full stack includes a database, a software application, a network of connected computers, and a consensus mechanism.
Sometimes the term refers specifically to the Bitcoin Blockchain or the Ethereum Blockchain, and sometimes to other virtual currencies, digital tokens, or enterprise distributed ledgers. In every case, the underlying idea is a shared, append only record that is replicated across many participants.
What Blockchain is NOT
Before diving deeper, it helps to clear up a few persistent misconceptions:
- Blockchain is not Bitcoin, but it is the technology behind Bitcoin.
- Bitcoin is the digital token, and the blockchain is the ledger that keeps track of who owns those tokens.
- You cannot have Bitcoin without blockchain, but you can have a blockchain without Bitcoin.
- Blockchain is not always anonymous. Most public chains are pseudonymous, meaning addresses are visible even when real identities are not.
Blockchain Architecture
Now let us study the blockchain architecture by breaking it down into its core components.
What is a Block?
A blockchain is a chain of blocks that contain information. The data stored inside a block depends on the type of blockchain.
For example, a Bitcoin block contains information about the sender, the receiver, and the number of bitcoins transferred.
Bitcoin Block
The first block in the chain is called the Genesis block. Every new block is linked to the previous block, forming the chain.
Understanding SHA-256 Hash
Every block also has a hash. A hash can be understood as a fingerprint that is unique to each block. It identifies a block and all of its contents, and it is always unique, just like a fingerprint. Once a block is created, any change inside the block will cause the hash to change.
What is SHA-256 Hash
The hash is therefore very useful when you want to detect changes. If the fingerprint of a block changes, it no longer represents the same block.
Each block stores:
- Data
- Hash
- Hash of the previous block
Consider the example below, where we have a chain of three blocks. The first block has no predecessor, so it does not store a hash of a previous block. Block 2 contains the hash of block 1, and block 3 contains the hash of block 2.
Every block contains the hash of the previous block. This is the technique that makes a blockchain so secure. Here is how it works.
Assume an attacker changes the data inside block 2. The hash of block 2 also changes. But block 3 still stores the old hash of block 2, which makes block 3 and every block after it invalid because the previous-block hashes no longer match.
Therefore, changing a single block can quickly invalidate every following block.
Consensus Mechanisms: Proof of Work and Proof of Stake
Hashes are an excellent mechanism to prevent tampering, but modern computers can calculate hundreds of thousands of hashes per second. In a matter of minutes, an attacker could tamper with a block and then recalculate all the hashes of other blocks to make the chain look valid again.
To stop this, blockchains use a consensus mechanism. The two most common families are Proof of Work and Proof of Stake.
Proof of Work (PoW) is a computational puzzle that takes significant effort to solve, but the result is quick to verify. In the case of Bitcoin, it takes about 10 minutes on average to calculate the required proof of work to add a new block to the chain. If a hacker wanted to alter block 2, they would need to redo the proof of work for that block and every block that followed.
Proof of Stake (PoS) is the newer approach used by Ethereum, Solana, Cardano, and most modern Layer 1 chains. Validators lock up, or stake, native tokens to earn the right to propose and validate blocks. Ethereum completed The Merge in September 2022, replacing Proof of Work with Proof of Stake and reducing the network energy footprint by roughly 99.95 percent.
Whether a chain uses PoW or PoS, the combination of hashing and consensus is what keeps a blockchain secure.
Distributed P2P Network
Blockchains also secure themselves by being distributed. Instead of using a central entity to manage the chain, blockchains use a distributed peer-to-peer network that anyone can join. When a participant enters the network, they receive a full copy of the blockchain, and each computer is called a node.
When any user creates a new block, that block is broadcast to every node on the network. Each node verifies the block to make sure it has not been altered. After verification, each node adds the block to its own copy of the chain.
The nodes in the network create a consensus. They agree on which blocks are valid and which are not. Nodes will reject blocks that look tampered.
To successfully tamper with a blockchain, an attacker would need to:
- Tamper with every block on the chain.
- Redo the proof of work or restake the required validator share for each block.
- Take control of more than 50 percent of the peer-to-peer network.
That combination is virtually impossible on a large public chain, which is why blockchains are considered so secure.
How Does Blockchain Technology Work?
Blockchain Transaction Process
A typical blockchain transaction follows four high level steps.
Step 1) A user requests a transaction. The transaction can involve cryptocurrency, smart contracts, records, or other information.
Step 2) The requested transaction is broadcast to a peer-to-peer network of nodes.
Step 3) The network of nodes validates the transaction and the user status using known consensus algorithms such as Proof of Work or Proof of Stake.
Step 4) Once validated, the transaction is bundled with others into a new block, which is then added to the existing chain in a way that is permanent and unalterable.
Why Do We Need Blockchain?
Here are some of the most important reasons why blockchain technology has become so popular.
Resilience: Blockchains use a replicated architecture. The chain keeps running even when many nodes go offline or are attacked, because most nodes still hold a valid copy.
Time Reduction: In the financial industry, blockchain enables faster settlement of trades because it removes the long verification, settlement, and clearance process. A single agreed-upon ledger is shared between all stakeholders.
Reliability: Blockchain certifies and verifies the identities of the interested parties. This removes duplicate records, reduces operational costs, and speeds up transactions.
Unchangeable Transactions: By registering transactions in chronological order, blockchain certifies the unalterability of all operations. Once a block is added to the chain, it cannot be removed or silently modified.
Fraud Prevention: Shared information and network consensus prevent losses caused by fraud or embezzlement. In logistics-based industries, blockchain functions as a real-time monitoring system that reduces costs.
Security: Attacking a traditional database means bringing down a specific target. With Distributed Ledger Technology, every party holds a copy of the original chain, so the system stays operational even if many nodes fail.
Transparency: Changes to public blockchains are visible to everyone, which creates strong transparency and makes transactions auditable.
Collaboration: Blockchain allows parties to transact directly with each other without the need for mediating third parties.
Decentralization: Standard rules govern how every node exchanges blockchain information, so all transactions are validated and added in a consistent order.
Blockchain Versions
Let us walk through the major eras of blockchain development.
Blockchain Versions
Blockchain 1.0: Currency
The implementation of Distributed Ledger Technology led to the first obvious application, which was cryptocurrency. This allowed financial transactions based on blockchain technology, primarily for currency and payments. Bitcoin is the most prominent example in this segment.
Blockchain 2.0: Smart Contracts
The next wave introduced smart contracts, small programs that live on the blockchain. They execute automatically and verify conditions defined in advance, such as facilitation, verification, or enforcement of an agreement. Smart contracts often replace, or at least automate parts of, traditional contracts.
Blockchain 3.0: DApps
DApp is an abbreviation of decentralized application. The backend logic of a DApp runs on a decentralized peer-to-peer network. A DApp can have a frontend written in any standard language that calls into its blockchain-based backend, similar in concept to a traditional web or mobile application.
Blockchain 4.0: Enterprise and AI Integration
The newest wave focuses on enterprise-grade scalability, interoperability between chains, and integration with artificial intelligence. Examples include tokenized real-world assets, Layer 2 rollups on Ethereum, central bank digital currencies, and using blockchains to record verifiable provenance for AI training data and model outputs.
Blockchain Variants
Public
In a public blockchain, ledgers are visible to everyone on the internet. Anyone can verify and add a block of transactions, and the network usually offers token incentives to participants. Bitcoin and Ethereum are public chains.
Private
A private blockchain lives within a single organization. It allows only specific people in that organization to verify and add transaction blocks, while read access can be restricted as needed.
Consortium
In a consortium blockchain, only a group of authorized organizations can verify and add transactions. The ledger can be open or restricted to selected groups. Consortium blockchains are common across industries such as banking, shipping, and healthcare.
Blockchain Use Cases
Blockchain technology is now used across a wide range of sectors, as shown in the table below.
| Sector | Usage |
|---|---|
| Markets |
|
| Government |
|
| Internet of Things (IoT) |
|
| Health |
|
| Science and Art |
|
| Finance and Accounting |
|
Important Real-Life Use Cases of Blockchain
1. Dubai: The Smart City
In 2016, the Smart Dubai office introduced a Blockchain strategy. Using this technology, entrepreneurs and developers can connect with investors and leading companies. The objective is to implement a blockchain-based system that supports many industries and helps make Dubai the happiest city in the world. If you want to build a career in this area, you can learn more about how to become a blockchain developer.
2. Incent Customer Retention
Incent is a Consumer Retention as a Service offering based on blockchain technology. It is a loyalty program that generates tokens for businesses inside an affiliated network. Tokens are exchanged instantly and can be stored in digital wallets on a phone or accessed through the browser.
3. Blockchain for Humanitarian Aid
In January 2017, the United Nations World Food Programme started a project called Building Blocks in the Sindh region of Pakistan. By using blockchain technology, beneficiaries received money and food, and every transaction was registered on a blockchain to ensure security and transparency.
4. Central Bank Digital Currencies
Countries including China, Brazil, and the European Union are running pilots of central bank digital currencies on blockchain or blockchain-inspired infrastructure. These projects aim to modernize payments while preserving central bank policy control.
Bitcoin Cryptocurrency: The Most Popular Application of Blockchain
What is Cryptocurrency?
A cryptocurrency is a medium of exchange similar to traditional currencies such as USD, but it is designed to exchange digital information through principles of cryptography. A cryptocurrency is a digital currency and is classified as a subset of alternative and virtual currencies.
Cryptocurrency is a bearer instrument based on digital cryptography. The holder of the currency has ownership, and no other record is kept about the identity of the owner. In 1998, Wei Dai published B-Money, an anonymous distributed electronic cash system that inspired later designs.
What is Bitcoin?
Bitcoin was launched in 2009 by an unknown person or group using the name Satoshi Nakamoto. Bitcoin is a peer-to-peer technology that is not governed by any central authority or bank. Issuance and transaction management are carried out collectively by the network.
It is presently the dominant cryptocurrency in the world. Bitcoin is open source and designed for the general public, which means nobody owns or controls it. The total supply is capped at 21 million coins. Bitcoin remains the largest cryptocurrency by market capitalization in 2026.
Anyone can use Bitcoin without paying high process fees, and the sender and receiver transact directly without using a third party.
Blockchain and Bitcoin
The blockchain is the technology behind Bitcoin. Bitcoin is the digital token, and blockchain is the ledger that keeps track of who owns those tokens. You cannot have Bitcoin without blockchain, but you can have blockchain without Bitcoin.
Other prominent cryptocurrencies include:
- Ethereum (now Proof of Stake)
- Solana
- Cardano
- XRP
- Bitcoin Cash
- Litecoin
Blockchain vs Shared Database
Blockchain vs Shared Database
| Parameters | Blockchain | Shared Database |
|---|---|---|
| Operations | Insert only | Create, Read, Update, and Delete |
| Replication | Full replication on every peer | Master-slave or multi-master |
| Consensus | Most peers must agree on the outcome of transactions | Distributed transactions using two-phase commit or Paxos |
| Validation | Global rules are enforced across the whole blockchain | Only local integrity constraints |
| Disintermediation | Allowed | Not allowed |
| Confidentiality | Configurable, often pseudonymous | Not fully confidential |
| Robustness | Highly robust | Less robust |
Myths About Blockchain
| Myth | Reality |
|---|---|
| It solves every problem | No, it is one type of database with specific tradeoffs |
| Trustless technology | It can shift trust and also distribute trust |
| Completely secure | It focuses on integrity, not confidentiality |
| Smart contracts are always legal | They only execute portions of some legal contracts |
| Immutable | It offers strong probabilistic immutability |
| Always wastes electricity | Proof of Stake chains like Ethereum use very little energy |
| Inherently unscalable | Modern Layer 2 networks and modular chains scale to thousands of transactions per second |
Applications of Blockchain Technology
Here are some common applications of blockchain.
- It is used to create a secure and transparent digital ledger of all transactions.
- It allows institutions to create a tamper-proof record of academic achievement that is accessible to students and teachers.
- It is used for creating a more efficient system for trading securities.
- Lenders use blockchain to execute collateralized loans through smart contracts.
- Using blockchain technology to record real estate transactions can provide a more secure way of verifying and transferring ownership.
- It is used for keeping verifiable identity attributes such as date of birth on a public ledger.
- Blockchain is used in logistics to track items as they move through a supply chain network.
- It is increasingly used for verifying the provenance of AI training data and the authenticity of model outputs.
Limitations of Blockchain Technology
Blockchain is powerful, but it is not a silver bullet. Here are the most common limitations to be aware of.
Higher Costs: Nodes seek higher rewards for completing transactions in a market that runs on supply and demand.
Slower Transactions: Nodes prioritize transactions with higher rewards, which can cause backlogs to build up during peak demand.
Smaller Ledgers: It is not always possible to maintain a full copy of the blockchain, which can affect immutability and consensus on lightweight nodes.
Transaction Costs and Network Speed: The transaction cost of Bitcoin is much higher than the nearly free fees promoted in its early years.
Risk of Error: There is always a risk of error when humans are involved. If a blockchain serves as a database, all incoming data must be high quality, because errors propagate widely.
Resource Use: Every node that runs a Proof of Work blockchain has to maintain consensus, which uses energy. Proof of Stake chains have significantly reduced this footprint.
Blockchain Council
Blockchain Council provides certifications for blockchain that are designed for people who want a career in the blockchain domain. The certifications require in-depth knowledge of core blockchain concepts and focus on Corda, smart contracts, Hyperledger, and Quorum applications.
Blockchain Council certifications are useful in industries like digital marketing, healthcare, and supply chain. The training and certifications are valuable for enterprises, businesses, and individual developers who want to apply blockchain to traditional working systems.
Certifications offered by Blockchain Council include:
- Certified Blockchain Expert
- Certified Corda Expert
- Certified Corda Architect
- Certified Blockchain Developer
- Certified Blockchain Security Professional
- Certified Smart Contract Developer
- Certified Bitcoin Expert
- Certified Ethereum Expert
If you want to learn about creating your own cryptocurrency, here is a free tutorial worth checking out: How to Create Your Own Cryptocurrency.
