Sometimes you might need your account's extended public key in a specific format for use with third-party services like watch-only wallets or tax reporting tools (e.g., Cointracking, Blockpit, Koinly). This guide explains what an extended public key is and how to convert it.

What is an extended public key?

Every cryptocurrency wallet you create with your BitBox starts with a seed phrase (usually 12 or 24 words). This seed is the foundation of your wallet.

• Deterministic Derivation: From this seed, your BitBox deterministically derives all your accounts and their respective addresses. Each account you see in the BitBoxApp (e.g., "Bitcoin 1," "Bitcoin 2") has its own unique Extended Public Key.
• Generating Addresses: From this account-specific Extended Public Key, an almost infinite number of individual receiving addresses are generated.
• Public Information: An extended public key allows viewing of all transactions and balances for that account but does not allow spending funds or accessing your private keys.

Extended public keys in your BitBox

By default, when you set up a new Bitcoin account in the BitBoxApp, it uses the modern Native SegWit (bech32, P2WPKH) standard.

• Address Type: You'll see receiving addresses starting with bc1q...
• Key Format: The corresponding Extended Public Key for these accounts is a zpub.

You can easily check this yourself:

1. In the BitBoxApp, select the desired Bitcoin account from the left-hand sidebar.
2. Click on "Account info" in the top right corner of the interface.
3. A window will pop up displaying the "Extended public key" details, including Account Name, Keypath, Script Type, Root Fingerprint, Coin, and the Extended Public Key itself.

Why convert an extended public key?

Different wallet software or financial services might expect different extended public key formats. For example, one service might require a zpub, while another needs an xpub or ypub. A Bitcoin Extended Public Key Converter tool allows you to change your key from one format to another.

Common formats include:

• xpub: For legacy (P2PKH) addresses.
• ypub: For SegWit compatible (P2SH-P2WPKH) addresses.
• zpub: For Native SegWit (P2WPKH) addresses (this is what BitBox uses by default for new accounts).
• tpub, upub, vpub: These are testnet versions of xpub, ypub, and zpub respectively.

How to use a Bitcoin Extended Public Key Converter

There are several converter tools available online (like the one on jlopp.github.io/xpub-converter/ – for maximum security, you can download and run such tools offline on a trusted computer).

Here’s a general guide on how they work:

1. Copy your key: From the BitBoxApp's "Account info" screen, copy your account's Extended Public Key (e.g., your zpub).
2. Paste your key: In the converter tool, find the input field (often labeled "Paste your extended public key here" or similar) and paste your key.
3. Select output format: Choose the format you need to convert to (e.g., xpub). This is usually a dropdown menu (e.g., "What version do you want to convert the extended public key into?").
4. Convert: Click the "Convert" button.
5. Use your converted key: The tool will display the converted extended public key (e.g., under "Converted extended public key:"). You can now copy this new key and use it with your desired third-party service.

Important: Public information only

Remember, this process leverages the transparent nature of the Bitcoin network. Your Extended Public Keys and individual receiving addresses are designed to be publicly viewable.

• View-Only Access: Sharing an extended public key (in any format) only allows others to see the transaction history and balances of that account.
• No Spending Power: It does not grant anyone the ability to sign transactions, spend your bitcoin, or access your wallet's private keys. Your funds remain secure in your BitBox.

By understanding and using these tools correctly, you can safely interact with a wider range of Bitcoin services while keeping your crypto secure.