HOW BLOCKCHAIN
ACTUALLY WORKS
The distributed ledger technology that makes crypto possible — and why it matters beyond finance.
⛓ What is a Blockchain?
A blockchain is a chain of "blocks," each containing a batch of transaction data. Every block references the hash (fingerprint) of the previous block, creating an unbreakable chain. To alter any historical record, you'd need to recalculate every subsequent block — which would require more computing power than the rest of the network combined.
This structure makes blockchains immutable (tamper-evident), transparent (anyone can verify), and decentralised (no single point of failure).
⚙️ Consensus Mechanisms
How does a decentralised network agree on the truth? Via consensus mechanisms:
Proof of Work (PoW): Miners compete to solve complex math puzzles. The winner adds the next block and earns a reward. Energy-intensive but battle-tested. Bitcoin uses this.
Proof of Stake (PoS): Validators lock up ("stake") crypto as collateral. They're randomly chosen to validate blocks. Much more energy efficient. Ethereum, Cardano.
Delegated PoS: Token holders vote for a set of delegates who validate. Faster but more centralised (EOS, TRON).
📜 Smart Contracts
Smart contracts are self-executing programs stored on a blockchain. When predefined conditions are met, they automatically execute — no middleman needed.
Example: A smart contract for escrow holds funds until both parties fulfil their obligations, then automatically releases payment — no lawyer required.
📡 Layers Explained
Layer 0: The underlying network infrastructure (e.g. Polkadot, Cosmos).
Layer 1 (Base Layer): The main blockchain — Bitcoin, Ethereum, Solana. Handles security and consensus.
Layer 2 (Scaling): Solutions built on top of Layer 1 to increase speed and reduce fees. Examples: Lightning Network (BTC), Polygon, Arbitrum, Optimism (ETH).
Layer 3: Application layer — dApps, games, and services built on top of L2s.
🔐 Cryptography Behind It All
Hashing: A hash function converts any data into a fixed-length string. Even changing one character completely changes the hash. Bitcoin uses SHA-256.
Public/Private Key Cryptography: Your private key mathematically generates your public key. Transactions signed with your private key can be verified by anyone using your public key — without revealing the private key.
Zero-Knowledge Proofs: Advanced cryptography that lets you prove you know something without revealing what it is. Used in privacy coins and scaling solutions.