About 14 minutes with practice. You only need something to take notes with. No real wallet details or payments are part of this lesson.
Course contents · Lesson 1 of 21
- Read the whitepaper as an argument · Marked complete
- Hashes and Merkle commitments · Marked complete
- UTXOs, change and accounting · Marked complete
- Scripts describe spending conditions · Marked complete
- Signatures and what they authorize · Marked complete
- Block headers and the chain of work · Marked complete
- Difficulty, hashrate and noisy observations · Marked complete
- Issuance, fees and incentives · Marked complete
- Mempools and policy are not consensus · Marked complete
- Fee changes: RBF and CPFP · Marked complete
- SegWit and transaction weight · Marked complete
- Taproot and Schnorr: useful, not magical · Marked complete
- HD wallets and derivation paths · Marked complete
- PSBT: separate construction from signing · Marked complete
- Descriptors make a wallet policy portable · Marked complete
- Full nodes, pruning and verification · Marked complete
- Reorganizations and lightweight evidence · Marked complete
- Lightning channels and HTLCs · Marked complete
- Lightning liquidity has direction · Marked complete
- Soft forks, proposals and human coordination · Marked complete
- Capstone: trace a payment end to end · Marked complete
What you will learn
- Connect double spending to a shared ordering problem.
- Separate the paper’s technical proposal from later implementations.
Start with the threat
The whitepaper asks how willing parties can transact digitally without making one intermediary the authority over payment history. A signature can establish authorization, but by itself does not reveal whether the same spend was offered elsewhere. The proposal therefore joins signatures with a public ordering mechanism and a way to compare competing histories.
Keep the assumptions visible
The paper analyzes an adversary trying to catch up with an honest chain. Its security discussion depends on assumptions about relative work and behavior. Read those assumptions before repeating the conclusion. The everyday phrase longest chain is best understood here through accumulated proof of work, not merely counting an arbitrary collection of blocks. A node still rejects a chain that violates its validation rules.
Read historically and technically
The document is a foundation, not a current wallet manual. Later improvements, deployed rules and operational experience belong in implementation documentation. When teaching it, annotate each paragraph as problem, mechanism, assumption or consequence. Avoid turning a technical statement about payment history into a guarantee about prices, human governance or charitable outcomes. Strong advocacy becomes more credible when it can explain the limits of its own evidence.
Practice on paper
Why are digital signatures alone insufficient to solve the problem described in the introduction? Write a two-sentence explanation for a technical newcomer.
Reveal the worked answer
A signature shows that the relevant key authorized a spend, but does not independently establish whether a conflicting spend exists. The network needs a shared way to establish which history to accept under its rules.
Check your understanding
Choose an answer in your head or on paper, then reveal the explanation. Retry whenever you like. Answers are not submitted or scored; completion marks are your own learning notes.
1. Does chain selection replace transaction validation?
- Yes
- No
Reveal answer 1
No. A candidate history must satisfy validation rules.
2. Is the whitepaper a current step-by-step wallet guide?
- Yes
- No
Reveal answer 2
No. It presents the foundational argument; implementations evolved.
Take this with you
Read the assumptions as carefully as the conclusion.
Your learning, at your pace
Read every lesson freely. Optional progress tracking needs JavaScript and browser storage; it does not require an account or wallet.
Remove the saved completion marks for this course on this browser? Other courses will stay unchanged.
Saved only in this browser for this website address. Clearing storage, changing device or using a different gateway may lose these marks. No sync, grading or credential; nothing is sent to us. The export is a record for you, not a file this site can import.