The blockchain
Course · Web3 · 3 min
What?01 / 08
The blockchain
An open ledger in the night: a public account book no one controls alone.
Three minutes to understand this ledger, why it changes trust — and how to read it yourself.
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What?02 / 08
Sealed pages
Every transaction is written on a page: a batch of exchanges, timestamped, waiting to be validated.
Once the page is full, it seals: we call it a block, and the ink never comes back out.
The seal is more than a closing: it carries the exact fingerprint of the page before it, reduced to a single signature.
Block after block, the fingerprints chain together — every page holds all the ones that came before it.
What?03 / 08
A thousand copies, one ledger
This ledger doesn't exist as a single copy in a drawer: it is copied, identically, onto thousands of machines around the world.
Every machine checks the same rules; an invalid page is rejected, even if someone tries to circulate it.
No one holds the original — the network follows the valid version selected by its consensus mechanism.
Why?04 / 08
Why it changes everything
Because you can trust someone without knowing them: two strangers exchange value without ever shaking hands.
Because no bank sits in the middle: no counter to convince, no account to open, no authorization to wait for.
Because the rule is the code — the same for everyone, readable by everyone, open twenty-four hours a day.
Forgery
Rejected
Why?05 / 08
Why it's so hard to cheat
Forging a single page breaks its fingerprint — and so every sealed page after it, all the way to the last one.
For the lie to hold, you would need to rewrite thousands of copies at once, faster than the rest of the network writes new ones.
On a large network, holding the advantage would demand immense resources — with no guarantee the attack could repay its cost.
How?06 / 08
How a transaction travels
Four steps are enough to carry a transaction, from the gesture to the sealed page:
- 01Signature — you approve the order with your key
- 02Broadcast — the network relays the order from machine to machine
- 03Validation — the nodes check that it follows the rules
- 04Sealing — the page closes, the fingerprint joins the chain
How?07 / 08
How to read a blockchain
Four habits are enough to consult the ledger yourself:
- 01Open a public explorer — the ledger is free to browse, no account or password needed
- 02Search an address — pasting its string of characters shows everything it holds and has done
- 03Read a transaction — amount, sender, recipient and fees are all displayed in plain sight
- 04Check its confirmations — the more blocks stack on top, the harder the page is to undo
Wallets
DEX
RWA
How?08 / 08
The foundation of it all
Step back: this ledger is not the destination, it is the foundation everything else is built on.
The wallet that signs, the exchange that compares two prices, the tokenized building split into shares — each is just a floor resting on this foundation.
You now know how to read the pages of the ledger; all that's left is to visit what has been built on it.