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Sikh Bitcoin · Advanced · Lesson 13 of 21

HD wallets and derivation paths

Understand reproducible keys without mistaking xpubs for harmless data.

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 13 of 21
  1. Read the whitepaper as an argument
  2. Hashes and Merkle commitments
  3. UTXOs, change and accounting
  4. Scripts describe spending conditions
  5. Signatures and what they authorize
  6. Block headers and the chain of work
  7. Difficulty, hashrate and noisy observations
  8. Issuance, fees and incentives
  9. Mempools and policy are not consensus
  10. Fee changes: RBF and CPFP
  11. SegWit and transaction weight
  12. Taproot and Schnorr: useful, not magical
  13. HD wallets and derivation paths
  14. PSBT: separate construction from signing
  15. Descriptors make a wallet policy portable
  16. Full nodes, pruning and verification
  17. Reorganizations and lightweight evidence
  18. Lightning channels and HTLCs
  19. Lightning liquidity has direction
  20. Soft forks, proposals and human coordination
  21. Capstone: trace a payment end to end

What you will learn

  • Explain a hierarchy of derived keys.
  • Identify why derivation metadata and xpub privacy matter.

A tree replaces isolated key records

BIP 32 defines hierarchical deterministic wallets: a seed can derive a tree of keys through indexed paths. Extended keys include information needed for child derivation. This helps wallets create many receiving addresses without requiring a separately improvised backup for every new address. A path identifies a position in the hierarchy, not a separate blockchain account.

Public derivation is useful and sensitive

An extended public key can derive corresponding non-hardened public descendants without spending authority. That makes watch-only receiving and monitoring possible. It can also reveal a broad set of addresses and their activity. Some combinations of exposed extended public information and private descendants have serious security consequences, which is one reason hardened derivation exists.

Recovery needs context

A seed alone does not always tell replacement software which script type, account or path the original wallet used. Store the required policy metadata securely according to the wallet’s recovery design. Never post a real xpub in a public support issue merely because it cannot independently sign. For a learning diagram, label a root, account branch, receiving branch and change branch without including actual key material.

Practice on paper

A shop wants an online server to generate receiving addresses without holding spending keys. What concept helps, and what privacy tradeoff remains?

Reveal the worked answer

A suitable extended public key or watch-only descriptor can support receiving-address generation. The server can still learn and expose the associated address history, so its scope and access should be limited.

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. Is an xpub equivalent to one ordinary receiving address?

  • Yes
  • No
Reveal answer 1

No. It can reveal a family of derived addresses.

2. Can every wallet infer all derivation choices from a seed alone?

  • Yes
  • No
Reveal answer 2

No. Recovery may require additional metadata.

Take this with you

Back up the policy context as well as the secret.

Your learning, at your pace

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