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Wallets and Key Management

A wallet does not literally store coins. It stores or manages the keys used to authorize spending. A distinction this section returns to repeatedly, because the "your Bitcoin is stored in your wallet" mental model, while a convenient simplification, obscures how backup, recovery, custody, and theft actually work. This section covers keys, seed phrases, hierarchical derivation, and the practical spectrum from hot wallets to cold, air-gapped storage.

What you need to know first

Private and Public Keys and Digital Signatures from the Cryptography section, and The UTXO Model from Bitcoin. This section is entirely about managing the keys those chapters already explained the mechanics of.

Every private key, seed phrase, and derivation example in this section uses either a trivial, clearly-fake test value (like the number 42) or the official, publicly documented BIP-39 all-zero test vector, never real, unpredictable entropy. Never reuse any value shown in this section for real funds.

Chapters

  1. Addresses: Base58Check, Bech32, and Bech32m, and why an address isn't a public key
  2. Private Keys: precisely what a wallet does and doesn't do with one
  3. Public Keys: when they become visible on-chain, and why that timing matters
  4. Seed Phrases: entropy to mnemonic to seed, verified against the official BIP-39 test vector
  5. BIP-39: the standard itself, the optional passphrase, and its real, documented risk
  6. HD Wallets: one seed, an unlimited deterministic tree of keys
  7. BIP-32: chain codes, hardened derivation, and a genuine xpub-related vulnerability
  8. BIP-44: the standardized path structure, and its purpose-field variants
  9. Derivation Paths: a practical reference for reading and troubleshooting them
  10. Hot Wallets: connectivity as the defining, not incidental, property
  11. Cold Storage: air-gapping and offline signing, concretely
  12. Hardware Wallets: secure elements and on-device transaction verification
  13. Multisig: script-based and Taproot-aggregated, and what each actually solves
  14. Custodial vs Non-Custodial Wallets: "not your keys, not your coins," unpacked precisely
  15. Key Backup and Recovery: the redundancy-versus-exposure tradeoff, and Shamir's Secret Sharing

Next

Continue to Bitcoin Scaling, which picks up the throughput questions this section's multisig and hot wallet chapters touched on, and builds toward the Lightning Network. A system that depends directly on the key and signature mechanics this section covered.