Introduction to Blockchain

Blockchain is the technology behind digital currencies like Bitcoin and Ethereum, which together have a combined market value of over $2.73 trillion as of 2025.

But blockchain goes beyond cryptocurrency — it enables secure, transparent transactions without intermediaries, transforming how industries operate.

What is Blockchain?

Blockchain is a decentralized, distributed ledger technology that records transactions across multiple nodes in a secure and tamper-proof manner. It is the foundation of cryptocurrencies like Bitcoin and Ethereum.

Key Components of Blockchain

• Blocks: Each block contains a set of transactions, a timestamp, and a reference (hash) to the previous block.
• Decentralization: Instead of a central authority, the blockchain is maintained by a distributed network of nodes (computers).
• Immutability: Once a block is added to the blockchain, altering any data would require changing all subsequent blocks, making it nearly impossible to tamper with.
• Consensus Mechanisms: Transactions are validated through different methods like Proof of Work (PoW) or Proof of Stake (PoS), ensuring the integrity of the network.
• Public & Verifiable: Each transaction on the blockchain can be viewed and verified by anyone. This transparency builds trust and removes the need for intermediaries.

The Building Blocks

Each block has three pieces of information in it:

• Data – The actual transaction details stored in the block.
• Previous block hash – A unique code linking it to the previous block.
• A new ‘hash’ for the current block – A unique code representing the block’s data.

A Chain of Blocks

In the case of a blockchain like Bitcoin, this data contains information of the sender, recipient, and the amount of money transferred.

The ‘hash’ is essentially a long string of characters (numbers and alphabets).
Each hash of a block is connected to the block before it.

It is because of this property that all blocks in the blockchain are connected to one another.

Genesis Block

The Genesis Block is the very first block on the blockchain — the point where it all begins.

Since there are no blocks before it, it has no previous hash, making it unique by design.

Hardcoded into the network, it marks the birth of the blockchain and sets the initial state for all future blocks.

Security

The strength of blockchain lies in its structure — if someone tries to tamper with the data in a block, the hash of that block changes.

Since each block is linked to the next using this hash, even a small change breaks the entire chain.

Every block's hash is tightly connected to the one that follows it. So, modifying one block affects all the blocks after it, making unauthorized changes easily detectable and practically impossible.

Consensus Mechanisms

One of the most critical aspects of blockchain is how all the nodes in the network agree on a single version of the truth — this is where consensus mechanisms come in.

A consensus mechanism is a protocol that ensures all participants in the network validate and agree on transactions before they’re added to the blockchain.

Some popular types of consensus mechanisms include:

• Proof of Work (PoW): Used by Bitcoin, this involves solving complex mathematical puzzles to validate transactions and add new blocks.
• Proof of Stake (PoS): Used by newer blockchains like Ethereum 2.0, this selects validators based on the amount of cryptocurrency they "stake" as collateral.
• Delegated Proof of Stake (DPoS): In this model, token holders vote for a few delegates to validate transactions on their behalf.

These mechanisms maintain trust, prevent double-spending, and keep the blockchain secure and decentralized without needing a central authority.

Conclusion

In this blog post, we explored the foundational concepts of blockchain technology:

• The basic structure of a block and how blocks are linked
• The genesis block as the starting point of every blockchain
• The security model that makes blockchain tamper-resistant
• The flow of transactions and how data is recorded
• The role of hashes in maintaining the integrity of the chain
• The importance of consensus mechanisms to validate and agree on transactions across a decentralized network

Together, these topics build a clear picture of how blockchain works under the hood — providing a strong foundation for diving into more advanced concepts in the future.