Most people now understand that metal seed backups are paramount, as paper burns. The challenge is how tostrongstore clear-text secrets? Anyone with physical access could use it and gain complete control of your funds! Encrypted digital backups are great, but they are not discrete and you could be compelled to produce the passphrase.
Enter Seed XOR, a plausibly deniable means of storing secrets in two or more parts that look and behave just like the original secret. One 24 or 12-word seed phrase becomes two or more parts that are also BIP-39 compatible seeds phrases. These should be backed up in your preferred method, metal or otherwise. These parts can be individually loaded with honeypot funds as each one is normal BIP-39 compatible wallet.
This one more solution for your game-theory arsenal.
Seed XOR!
— Trumby_Hodl (@Trumby_Ray) July 8, 2024
A Magical Way to Split Your Key into Two Parts!
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Q: I'm lazy, can I do this to my Existing Seed?
A:Yes. You can split the words you have from the menu on your existing Coldcard. You could also any number of existing SEEDPLATES you have already, and combine them to make a new random wallet that is the XOR of their values.
- any combination of found seed word phrases is a fully working wallet (great for duress)
- each part is 24 or 12 words, and can be encoded onto a SEEDPLATE
- all parts are required to be known to get back to original seed phrase (not M of N, always N of N),
- your existing seed can be split by Coldcard (the one already in use)
- take 2 or more existing SEEDPLATE’s and combine them into a new random wallet just by importing them using Seed XOR.
- you can do the math on paper, and it’s possible to split/combine without the Coldcard
- see docs/seed-xor.md for background
- paper worksheet you will need are available at wordlist-paper along with the python code that generates them.
- look for Seed XOR option when importing into a blank Coldcard, and see Advanced > Danger Zone > Seed Functions > Seed XOR for use on a setup Coldcard.
PS: We made a discount bundle for 3x SEEDPLATES + COLDCARD + Industrial MicroSD + Tamper Evident Bags to cover this whole scenario.
Printable Resources
- Printable 24 words worksheet (PDF, one page) for you to print and use when calculating your own XOR by hand.
- Printable 12 words worksheet (PDF, one page)
- BIP-39 Wordlist (PDF, four pages) with hex values for each word. It's formated as a table, so you could cut it up into 2048 pieces.
Guides
Bitcoin Magazine: How To Protect Your Bitcoin With Coldcard And Integrated Seed XOR by @econoalchemist
Video by BTCSessions
Video by @KISBitcoin