COLDCARD Seed XOR

Seed XOR – Split your secret BIP-39 seed into 2 or more new seed phrases

Most people understand that metal seed backups are paramount, as paper burns. The challenge is how to store these cleartext 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-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 24 words, with the 24th being the checksum and will work as such in any normal BIP-39 compatible wallet.

This one more solution for your game-theory arsenal.

  • any combination of found seed word phrases is a fully working wallet (great for duress)
  • each part is still 24 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.

We’ve made a mini-site for Seed XOR with more background, links to these resources and more.

PS: We made a discount bundle for 3x SEEDPLATES + COLDCARD + Industrial MicroSD + Tamper Evident Bags to cover this whole scenario.

Enhancements

  • Adds support for BIP-48 derivations when exporting generic JSON (including the accounts number) under Advanced > MicroSD Card > Export Wallet > Generic JSON. These are targeted towards multisig wallets, such as Sparrow.
  • Ask for account number when creating Multisig Wallets via air-gapped Coldcards. Use account zero for compatibility with previous versions. No need to use same account number on each participating Coldcard, but we recommend that. Creating new P2SH (BIP-45) type air-gapped wallets has been removed since it cannot support multiple accounts.
  • Show new firmware version number and date before installing firmware update.

Bug Fixes

  • Could not clear PIN codes, including the duress PIN, so was not possible to wipe the main secret, if a duress PIN had been set. 999999-999999 works again now.
  • Deleting a multisig wallet that was identical to another wallet, except for different address type, would lead to an error.
  • Standardize on BIP-nn in place of BIPnn in source code, messages and docs.

Download the latest firmware

Get COLDCARD Mark 3

Video Tutorials

We have a growing library of video tutorials on Youtube … and we’re still adding more!