I'm working on a safe way to store a mnemonic key.
- It's 24 words long.
- Each word is 11 bits of entropy
- I want to store it in 3 locations
- One plate should not allow you to unlock the code
- Two plates should allow you to unlock the code
Now to the interesting challenges:
- If I die, I want my loved ones to be able to extract the mnemonic keys. They know nothing of cryptography.
- To protect it from fire, I'm etching it on metallic plates so the instructions for unlocking can't be to long or complicated.
- I want it to last for at least 100 years, so I can't rely on any current computer software.
My fist idea was to just leave 8 different words out of each plate, but that is just 88 bits of entropy, a bit to little to crack(or is it). There are also tools to do Shamir's Secret Sharing Scheme, with mnemonic phrases, but it's not really something you do without a computer. Is there some other good way to increase the bits of entropy without to much complication? Maybe mixing up the words or add extra words or something?