2. How Blockchain Works
HODL Guide Pro · Crypto 101
Module 2 of 12
Module 2 of 12
How Blockchain Works
You don’t need to be technical to understand the engine under crypto. Here’s how a blockchain records transactions and stays tamper-proof — in five minutes.
Blocks, chained together
Transactions are grouped into blocks. Each block carries a unique fingerprint (a hash) and also records the fingerprint of the block before it. That’s the “chain.” Change anything in an old block and its fingerprint changes, which breaks every block after it — so tampering is obvious to the whole network.
Figure. The “chain” is just each block referencing the fingerprint of the previous one.
Who agrees on the truth? Consensus.
Thousands of computers (nodes) hold copies of the chain and must agree before a block is added. Two main methods secure this:
| Method | How it secures the network | Trade-off |
|---|---|---|
| Proof of Work | Miners spend computing power solving puzzles (Bitcoin) | Very secure; energy-intensive |
| Proof of Stake | Validators lock up coins as collateral (Ethereum) | Energy-light; newer model |
Either way, cheating costs more than it’s worth — that’s the security. Once enough nodes confirm a block, it’s immutable: effectively permanent.
Key takeaways
- Blocks are chained by cryptographic fingerprints — tampering is instantly visible.
- A distributed network agrees on truth via Proof of Work or Proof of Stake.
- Confirmed transactions are permanent. There’s no undo button.
Educational purposes only — not financial, investment, or tax advice. Crypto is volatile; rules vary by country and change often. HODL Guide never asks for your seed phrase or private keys. Some links may be affiliate links; this never influences our reviews or rankings.