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LESSONS

Keys and addresses

A seed derives private keys, which derive public keys and addresses. Only the seed needs backing up; only addresses should be shared.

5 MIN READ
COURSE · Self-custody essentialsSTAGE 3 · OWN ITLESSON 1 OF 10
Seed phrase derives private keys, public keys and addresses, each step one-way.
LEVEL · Intermediate
IN THIS LESSON · 1 OF 10
BY THE END YOU WILL BE ABLE TO ANSWER
  • Which can you safely give to someone paying you?
  • What does an xpub reveal?

Then prove it: a 2-question quiz. The lesson marks itself complete at 100%.

Everything in self-custody follows from one fact: control of bitcoin is control of a private key, and a modern wallet derives all its private keys from one seed.

The derivation chain

  • Seed phrase: 12 or 24 words (BIP 39) encoding random bits. The root.
  • Private keys: derived from the seed in a tree (BIP 32), one per address, unlimited.
  • Public keys: derived one-way from each private key.
  • Addresses: a hash of the public key, encoded with a checksum. bc1q for native SegWit, bc1p for Taproot; older 1 and 3 formats still work.

Each arrow runs one way. From the words you can regenerate everything; from an address you can get nothing.

What to share

  • Address: freely, one per payment.
  • Extended public key (xpub): reveals every address and balance in the wallet; share only with software you trust to watch it.
  • Seed and private keys: never, with anyone, for any reason.

Why address reuse hurts

Every address is public forever. Reuse one and everyone who paid you can see everyone else who paid you, and your total. Wallets generate fresh addresses automatically; let them.

Tap a card to flip it.

CHECK YOURSELF
1/2 Which can you safely give to someone paying you?
2/2 What does an xpub reveal?
pick an answer for each question

SOURCES

  1. BIP 32: Hierarchical Deterministic Wallets
  2. BIP 39: Mnemonic code for generating deterministic keys
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