Single seed multi-location backup schemes
The aim is to create 3 packages of cryptographically secure backups where the funds cannot be recovered from any single package, but can be recovered with the combination of any two.
Can be thought of as a physical 2-of-3 multisig solution.
SeedXOR
SpecterDIY
ColdCard
JoinMarket
LND
Samourai Wallet
Electrum Wallet seed as a passphrase
A well proven way to generate a random 12 word list is to create a new wallet seed in Electrum Wallet.
To use Electrum boot Tails (ideally offline) or download and verify the wallet on an existing system.
Follow steps 1-5 in this guide to get the seed. The wallet file is not needed, only write down the words and store them accordingly. The 12 words are to be used as a passphrase, encryption passphrase, cypher phrase or wallet unlock password. Do not reuse passphrases for more than one purpose and label the backups clearly.
The Electrum word list is based on the same 2048 words as the BIP39 word list which the ColdCard firmware contains so the keyboard entry is facilitated by the menu.
An Electrum Wallet seed provides 135 bits of entropy which is stronger than a 12 word BIP39 seed.