BIP-85 Wallets

With BIP-85, you can derive multiple Bitcoin keys from your single, primary backup.

"One Seed to rule them all, One Key to find them, One Path to bring them all, And in cryptography bind them."

Using the Coldcard, you can create multiple additional backups, different from the original created during the device initialization. The entropy is derived using the Coldcard backup and can be imported into other wallets.

This is a deterministic process, so you can recover these new wallets using the Coldcard's original backup. One cannot reverse a new bitcoin wallet created with BIP-85 to obtain the Coldcard's original backup.

The derived wallet is completely separate from the COLDCARD so your original wallet and any other derived wallets will still be safe.

Available export formats:

• BIP-39

• 12 seed words

• 18 seed words

• 24 seed words

• WIF (private key)

• XPRV (BIP-32)

• Hex

• 32 bytes

• 64 bytes

Steps:

1. Select 'Advanced'

2. Select 'Derive Entropy' and read the displayed message. Press OK to continue.

3. Select a backup format.

4. Enter an index number. This can be any number between 0 and 9999. Write down this index number in case you need to recover this seed in the future. Press OK when you're done.

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:

   1. Press 1 to save the value to a microSD card

   2. Press 2 to use the derived seed, temporarily, on your COLDCARD (BIP-32 and BIP-39 only)

   3. Press 3 to show the value's QR code

Import the derived seed into the wallet of your choice.

Tips

• You can use this feature on a seed with a BIP-39 passphrase. However, access to the derived seed will require that same passphrase in the future if you ever need to restore it. This can complicate the recovery process, so you may want to avoid deriving entropy from passphrase-protected seeds by using the Derive Entropy function before entering your passphrase.
• If you forget the index number, it's possible to search for the correct index because there are only 10,000 possible choices.

• 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.