Steps for Seed XOR
We will be splitting the main seed phrase into two parts.Steps:
Select Advanced
Select Danger Zone
Select Seed functions
Select Seed XOR
Select Split existing seed
Press 2
Press OK
If any parts are lost, then funds are lost if you do not still have in your possession your Coldcard or the original seed phrase with the passphrase.
Make sure to store the 24th word of your original seed phrase alongside both parts obtained through Seed XOR. This allows you to be sure you've gotten all the parts and assembled them correctly.
Take out a pen and paper
Two lists of words (A and B) will be generated. Write down each list in their respective order.
Press on the checkmark when done.
Complete the test to make sure that you have correctly written them down.
The seed is now split into two parts!
Using the Seed XOR function in your Coldcard allows you to separate your original seed phrase into two parts, each looking like it’s own 24-word seed phrase. Combining them will produce your original 24-word seed phrase.
You will need both parts generated with Seed XOR in order to recover your original seed phrase.
You will also need your passphrase to access the wallet containing your funds.
Each Seed XOR component can also function as a Bitcoin seed phrase. You can keep some funds on it to satisfy a potential attacker or to alert you that your storage is compromised if someone finds it and takes the funds held on it.
In your Coldcard device go to:
Advanced
Danger Zone
Seed functions
Seed XOR
Restore Seed XOR
OK
Enter the words from list A
At the 24th word, The Coldcard will display a short list of words for you to choose the correct word from.
Repeat for list B
You must have both parts in order to restore your seed phrase. The order in which you enter them (either seed XOR A or B) does not matter.
The imported seed XOR will only remain temporarily.
You will be asked if you want to use the existing seed by pressing on 1 - DON’T, press OK
Follow the instructions below if you are restoring your seed on a new, uninitialized Coldcard device.
Import Existing
Seed XOR
Enter one of the parts (lis A or B)
When done, press on 1 to enter the next part
Enter the other list of words
Confirm that the 24th word of your original seed phrase is correct
Press 2 to complete the import
To verify the imported seed:
Use this to see the backup stored in the device and if it matches the original that you have written down.
Advanced
Danger Zone
Seed functions
View Seed Words
OK
It is possible to recreate your original backup using the two seed XOR word lists by hand. Follow the intructions below to do so:
Using this worksheet, enter the words from the two lists that have been generated using seed XOR on your Coldcard.
Using this wordlist, write down the 3-digit hex code associated with each word in your worksheet.
Once lists A and B have been written down in the worksheet, use the table in your worksheet to complete the A + B row.
To do so, associate the hex digits of each word from list A with those from list B.
Whether you look up the row or column first does not change anything since it will produce the same value.
Enter the digit that you obtain from the table in your worksheet. At the end of the process, you will have a new hex code.
Using the wordlist and the newly generated hex codes, retrieve the words that form your seed phrase.