This is the part where the safety nets come down. No pretests, no warm-up analogies, no “guess before reading” — just the course, asking whether any of it stuck. Everything you need, the previous eight lessons already taught you. Read each option twice; the trap is usually the one that’s 90% right.
How this exam works
This is a graded exam. Questions come one at a time. Once you submit an answer it is final — there is no going back, no second try, and a wrong answer simply fails that question. Your score stays hidden until the end, where you need 70% to pass. Read every option twice before you commit.
A friend insists 'Bitcoin is totally anonymous — nobody can ever know it's me.' What is the precise correction?
Select an answer to continue.
Course Recap
Big picture
The complete Bitcoin mental model
- Bitcoin, end to end
- What Bitcoin is
- No central issuer, genesis 2009
- Solves digital double-spending
- Pseudonymous, not anonymous
- 1 BTC = 100,000,000 satoshis, divisible
- Ledger & mining
- ~10-min blocks, mempool of pending txs
- Users sign txs, miners select & order
- Header: prev hash, Merkle root, nonce, target
- Subsidy + fees pay the miner
- Difficulty retargets every 2016 blocks
- Proof-of-work
- Grind nonce, hash below target
- Hard to produce, trivial to verify
- Heaviest-work chain wins, orphans return
- 51% can reorg/censor, cannot forge or mint
- Supply & halvings
- 21M hard cap
- Subsidy halves every 210,000 blocks
- 50 → 25 → 12.5 → 6.25 → 3.125
- Disinflationary; ~2140 fees only
- Keys & wallets
- Private → public → address (secp256k1)
- Signatures prove ownership, hide the key
- Seed phrase backs up all keys
- Not your keys, not your coins
- Transactions & fees
- UTXO model, inputs + outputs + change
- Fee = inputs − outputs, paid to miner
- Priced by size (sat/vByte), not amount
- Confirmations, RBF / CPFP to unstick
- Nodes & verification
- Full node validates every rule
- Rejects invalid blocks, even from miners
- Nodes verify, miners produce
- SPV trusts nodes; more nodes = resilience
- Lightning Network
- Layer 2: open + close are on-chain
- Off-chain balance updates, instant & cheap
- Non-custodial, cheating is penalized
- HTLC routing is atomic; needs liquidity
- What Bitcoin is
Key Takeaways
What to remember
- Bitcoin is pseudonymous money with no issuer — it solved digital double-spending in 2009 by ordering every transaction in one public ledger, and it’s divisible down to 100 million satoshis per coin.
- Mining is a verifiable lottery — miners grind the nonce until the header hashes below target, the heaviest-work chain wins, and difficulty retargets every 2016 blocks to hold the ~10-minute pace. A 51% majority can reorg and censor, but can never forge signatures or mint beyond schedule.
- The supply is fixed at 21 million — the subsidy halves every 210,000 blocks (50 → 25 → 12.5 → 6.25 …), making Bitcoin disinflationary; around 2140 it hits zero and miners live on fees, but mining never stops.
- You control coins through keys, not files — private → public → address is one-way; the address is safe to share, the seed phrase never is, and losing it loses the coins forever. Not your keys, not your coins.
- Transactions are UTXOs with a fee priced by size — inputs minus outputs is the miner’s fee in sat/vByte, change comes back to you, and confirmations (≈6) plus RBF/CPFP govern settlement and stuck payments.
- Full nodes verify; Lightning scales — a node rejects any invalid block even from a miner, while Lightning settles instant, near-free off-chain payments between two on-chain transactions, non-custodial and anchored to the base chain.