Unit 2 · Level 1 · Wallets & keys
Anatomy of a transaction
Every crypto transaction makes the same journey: your private key signs it, your wallet broadcasts it to the network, and validators pack it into a block. Each new block on top adds a confirmation, until the transaction reaches finality, carved into the ledger for good. Powerful, but unforgiving: send to the wrong address and no one can pull it back.
Free to play. No ads, no token, no account needed to start.
What you get asked
Put the life of a transaction in order
Sign → broadcast → wait → included → final. The fee is your bid for a seat in the next block.
Why does the same transfer cost €0.50 one day and €15 another?
Gas fees are an auction for limited block space. Quiet network, cheap seats; NFT-mint frenzy, everyone outbids everyone.
A simple ETH transfer uses 21,000 gas. At today's gas price that adds up to 0.002 ETH, and ETH trades at €2,000. What does the transfer cost in euros?
0.002 ETH × €2,000 = €4. Always sanity-check the fee in euros before you hit send. Wallets show it, but eyes glaze over.
You send €500 of crypto to a mistyped address. What happens?
There's no bank to call; finality cuts both ways. That's why careful senders paste the address, check the first and last characters, and test with a small amount first.
After enough confirmations a transaction reaches ___, the point where it can never be rolled back.
Finality is the chain's way of saying "done means done." Great for trust, brutal for typos. Check twice, send once. 🐜
The rest of this unit
Keys, seed phrases, and custody: how to truly own your coins.