1. Write down the passphrase you want to use before entering it in your computer.

2. Select “Passphrase”.

3. Select the following:

   • Add Word

   • You will have a selection of words to choose from, taken from the BIP39 wordlist.

   • Select at least 4 different words, and choose up to 12.

   • Find the word you want by first selecting its first letter. You will also have the option to add a space before or after the word and if you want to use upper or lower case letters.

4. Once entered, select “APPLY”.

5. A new wallet identifier, also called a fingerprint, will be created. Note this down.

6. Press on the check mark.

This function effectively destroys your original BIP-39 seed in the Coldcard's secure element and replaces it with the extended private master key (XPRV) value for your seed words and passphrase. You end up with a BIP-32 HD wallet.

Steps

1. Select Advanced

2. Select Danger Zone

3. Select Lock Down Seed

4. Read the confirmation message on your screen

5. Press OK (✔) to confirm. Your COLDCARD will restart to lock down the seed.

6. Enter your PIN. The Passphrase option will not appear in the menu.

How can this be useful?

You may need to create multiple wallets based on the same seed words for delegation to other people. Save a backup file from the default wallet created by your set of seed words. Get the required number of COLDCARDs, choose Import Existing during setup and load the same backup file onto each of them. Give each COLDCARD its own passphrase and then lock down the seed. Your seed words will not be known to any of the devices and remain secure. -Coldcard docs