Guides / Glossary / Extended public key
Glossary

Extended public key (xpub): what it reveals and what it cannot do

A public key that can generate a whole family of receiving addresses. It can show balances but it cannot sign.

Education only

Definition. A public key that can generate a whole family of receiving addresses (often called an xpub). It can show balances but cannot sign.

How it works

BIP 32 describes hierarchical deterministic wallets, in which one master key generates a tree of child keys. An extended public key, usually shortened to xpub (or with other prefixes for newer address types), sits at a point in that tree. From it, software can work out every public key and address below that point, without any private key.

In a multisig wallet, each signing device exports its extended public key during set up. The wallet software combines the extended public keys with the threshold to make the wallet's addresses. That combination is what the descriptor records.

Why it matters for a company

An extended public key cannot sign, so it cannot be used to steal coins directly. But it is not harmless. Anyone who holds it can see every address the wallet has used or will use, and so every incoming payment and the full balance. For a company, that is commercially sensitive information, and it can make the company a target for scams or physical threats.

There is also a technical caution. BIP 32 notes that an extended public key combined with any single child private key from below it can reveal the parent private key, for keys derived in the non hardened way. Good wallet software handles this, but it is one reason never to export child private keys casually.

For accounting, an extended public key or descriptor is useful. It allows a watch-only wallet, so the bookkeeper and auditor can reconcile balances without access to signing devices.

Example only, fictional. A company gives its outsourced bookkeeper a watch-only wallet built from the descriptor, under a confidentiality clause in the engagement letter, and notes the disclosure in the key register.

Common mistakes

Sources

Primary sources only. Each link was checked on 9 November 2026. Rules change, so confirm the current version with your adviser.

  1. Bitcoin BIPsBIP 32: Hierarchical deterministic wallets (extended keys)
  2. Bitcoin BIPsBIP 380: Output script descriptors, general operation (wallet backups and exports)
  3. Bitcoin developer documentationWallets guide: signing-only wallets and hardware wallets
Education, not advice.

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