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Export Deterministic Entropy (BIP-85)

Video: BIP85: Segregated Bitcoin Accounts From One Seed

COLDCARD® can generate new sets of BIP-39 seed words and other seed types by exporting entropy according to BIP-85. This entropy is mathematically derived from your COLDCARD's seed value and easily imported into other wallet systems.

Available export formats:

  • BIP-39
    • 12 words
    • 18 words
    • 24 words
  • WIF (private key)
  • XPRV (BIP-32)
  • Hex
    • 32 bytes
    • 64 bytes
  • Passwords

Because this is a deterministic process, you can recreate a child from the same parent wallet and BIP-85 application, format, and index. If a BIP-39 passphrase was active when the child was derived, the exact passphrase is also required. Preserve that recovery context with the parent backup.

A child cannot be used to derive the parent through the BIP-85 construction. The reverse is not true: anyone who obtains the parent wallet and derivation context can reproduce every child below it.

Protect the Parent for Every Child

Protect the parent for the combined value and privacy of all derived wallets. Before deriving children, check the current security status and create the parent on fixed firmware using the standard Dice Rolls option. For a combined amount whose loss would be materially harmful to you, use a strong, unique BIP-39 passphrase, back it up separately, record the parent wallet fingerprint, and test that the same parent context and index reproduce the child before funding it. Adding or changing the parent passphrase creates different children.

Read the BIP-85 (Deterministic Entropy From BIP-32 Keychains) for more detail and other applications.

Using the Derive Entropy Function#

  1. Connect your COLDCARD to power and log in normally.

  2. Select Advanced/Tools > Derive Seed B85 on Mk4, or Advanced/Tools > Derive Seeds (BIP-85) on Q, and read the displayed message. Press ✔/ENTER to continue.

    mk4 nav to bip85 q nav to bip85

  3. Select a seed format.

  4. Enter an index number. This can be any number between 0 and 9999 (for larger index numbers see Derive Entropy Tips). Write down this index number in case you need to recover this seed in the future. Press ✔/ENTER when you're done.

    mk4 create seed q create seed

  5. The derived seed value and other information will appear on the screen. Scroll down to see the available options. The options available depend on the chosen seed format:

    • Press 1 to save the value to a MicroSD card (slot A on the Q)
    • Press B on the Q to save to MicroSD card slot B
    • Press 2 to save to the Virtual Disk (must be enabled)
    • Press 3 on the Mk4, or the NFC key on the Q to send by NFC (must be enabled)
    • Press 4 on the Mk4, or the QR key on the Q to show the value's QR code
    • Press 6 to type the derived value into a connected computer using USB keyboard emulation
    • Press 0 to use the derived seed, temporarily, on your COLDCARD (BIP-32 and BIP-39 only) Video: How to use BIP-85 Child Seeds with COLDCARD and other Bitcoin Wallets
  6. Import the derived seed into the wallet of your choice.

If the derived wallet will hold an amount whose loss would be materially harmful to you and the destination supports BIP-39 passphrases, apply a strong, unique passphrase there as well. BIP-85 reproduces the child seed, not that destination passphrase, so back it up separately and test recovery before depositing funds.

Thanks go to Ethan Kosakovsky for creating this useful standard, and for accepting our additions as the standard was being refined.

Derive Entropy Tips#

  • You can use this feature on a seed with a BIP-39 passphrase. The exact passphrase and parent wallet fingerprint then become part of the recovery context. Test that you can re-enter that context and reproduce the child before funding it.

    mk4 bip85 from passphrase q bip85 from passphrase

  • You can also derive entropy from Temporary Seeds while they are in use. Although, just like passphrases, the same Temporary Seed will be required if you need to restore the derived entropy later. For this reason, you may also want to avoid using this feature on Temporary Seeds.

    mk4 bip85 from temp seed q bip85 from temp seed

  • If you forget the index number, it's possible to search for the correct index because by design COLDCARD only allows BIP-85 indexes up to 9999.

  • Derived XPRVs or BIP-39 seed words (12, 18, or 24) can be used on another COLDCARD.
  • Temporarily using the derived seed on your COLDCARD allows you to sign PSBT files associated with the derived wallet. The key stays in effect until next you turn off the COLDCARD or log out. You will probably need to consult Walletrecovery.org in order to build specialized PSBT files for recovery purposes.
  • To enable the use of index numbers higher than 9999, you must set: Advanced/Tools > Danger Zone > B85 Idx Values > Unlimited.
Last update: August 27, 2026