Keys, addresses, wallets, and custody

Control keys safely and understand every encoding layer.

Follow these 12 lessons in order, or choose the topic you need. Each lesson combines an explanation, a worked example and practice inside the Guild.

1. Private and public keys

   A private key is the secret that authorizes a spend. A public key lets others verify that authorization, while an address describes where a payment can be locked.

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2. Base58, Bech32, and Bech32m

   Bitcoin addresses are human-readable encodings with a network marker and error-detecting checksum. Three formats exist because Bitcoin added new spending types over time.

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3. BIP39 mnemonics and passphrases

   Bitcoin Improvement Proposal 39 defines word-based wallet backups. Its optional passphrase creates a different wallet, so losing either the words or passphrase prevents recovery.

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4. HD derivation

   A hierarchical deterministic wallet creates many related keys from one root. Bitcoin Improvement Proposal 32 defines normal and hardened child-key paths with different exposure risks.

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5. Descriptors and miniscript policy

   A wallet descriptor is a precise recipe for finding keys and constructing spending conditions. Miniscript is a structured way to express some of those conditions safely.

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6. Watch-only and air-gapped workflows

   A watch-only wallet can observe funds and build transactions without private keys. An offline signer can then review and authorize the exact transaction.

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7. PSBT

   A Partially Signed Bitcoin Transaction, called a PSBT, carries one unsigned transaction plus the metadata signers need to review, sign, combine, and finalize it.

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8. Multisig and threshold custody

   A multisignature script asks Bitcoin to verify several visible signatures. Threshold signing instead lets several participants cooperate to produce one group signature.

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9. Backups and recovery

   Recovery requires more than seed words. A complete plan preserves every passphrase, key path, spending policy, and quorum rule needed to recreate and test the wallet.

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10. Private keys, public keys, and key hashes

    Inspect valid scalar bounds, compressed curve points, public-key hashes, authorization, and the difference between a key, address, script, and spendable output.

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11. WIF, Base58Check, Bech32, Bech32m, and checksums

    Encode and decode private-key and destination text formats byte by byte, including network markers, witness versions, conversion alphabets, and checksum limits.

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12. HD wallet trees and extended-key anatomy

    Decode xpub and xprv fields, derive BIP44, BIP49, BIP84, and BIP86 branches, and identify what recovery metadata and public-key exposure imply.

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