Definition
BIP32 defines hierarchical deterministic (HD) wallets, the architecture behind nearly every modern Bitcoin wallet. Instead of generating and separately backing up unrelated private keys, an HD wallet derives a whole tree of keys from one master seed. The seed (128-512 bits of entropy) is run through HMAC-SHA512 with the key string "Bitcoin seed" to produce a master private key and a 256-bit chain code. From that root, child keys descend in a structured tree, each addressable by a path such as m/0/1.
Why a single backup is enough
Because every key is reproducible from the seed, you only need to back up that seed once (commonly as a BIP39 mnemonic). Restore the seed into any compatible wallet and it regenerates the same addresses, balances, and spending keys. This is what makes a 12- or 24-word phrase a complete wallet backup rather than just one key among many.
The chain code and extension
Each key is "extended" with the chain code, giving 256 extra bits of entropy that feed the derivation of children. An extended private key can derive both child private and public keys; an extended public key (the xpub) can derive child public keys only, which enables watch-only and receive-only setups without exposing spending authority.
BIP32 is the foundation for path conventions like BIP44 and for extended public keys (xpub), and it underpins the hardened derivation safeguards that protect a parent key from a leaked child. We treat correct HD-wallet handling as core to self-custody hygiene for sovereign Bitcoiners.
In Simple Terms
BIP32 defines hierarchical deterministic (HD) wallets, the architecture behind nearly every modern Bitcoin wallet. Instead of generating and separately backing up unrelated private keys, an…