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One Time Pad or XOR is an elegant and information-theoretic secure [1] way to split a BIP39 seed. It's a method simple to describe (apt for a will), easy to verify (trust only yourself) and the resulting shares are mnemonics thus easy to record. Best of all it can be computed entirely with paper and pencil eliminating risks from malware. The method does not ...


6

One can use Shamir's Secret Sharing Scheme, but the input ASCII string must be under 128 ASCII characters in length. Fortunately, the 2048 English BIP 39 words are guaranteed to be unique from their 1st four characters, sometimes even fewer characters. Let's assume the 24 recovery words are "bunker wreck real edge inflict aerobic buddy mercy divorce wolf ...


2

The only reason I can think of that would result in the above with a valid OTP seed is invalid OTP settings (but default should work for Google Auth) OR incorrect time on the device OR invalid time (drifted) on the GreenAddress service clock. I checked for the last one personally and the services clock is fine: in my experience most of the time is time/...


2

Here's a 3 of 5 one time pad solution with just 2 series (A is a random key, B is a random key, C is Real⊕A⊕B, Real is A⊕B⊕C. Thanks to @answerevaded, @oisyn, and @Scooper this is just a simplification for the 3 of 5 case: {A1, A2}, {B1, B2}, {C1, A2}, {B1, C2}, {A1, C2} Implementation in any language is simple, which is why I prefer this solution to SSS: ...


2

There are at least three practical tools implementing Shamir Secret Sharing with BIP39 mnemonics: https://github.com/iancoleman/slip39/ https://github.com/unchained-capital/hermit https://github.com/trezor/python-shamir-mnemonic/


1

In the Electrum wallet for pc, it is possible to modify a wallet from normal password to 2fA (two factor authentication ) without creating a new wallet? No, it is not possible to add two-factor authentication to an existing wallet. these are two different wallet types. the fee for the 2fA it's billed only when sending funds from the 2fA wallet to ...


1

The answer by answerevaded seems the safest solution to the problem. In addition to his scale examples for "n of n" and "2 out of 3", here is the example for "3 out of 5": For "3 out of 5" you need to create 10 random keys in the way answerevaded explains the "3 of 3" system. This will result in keys A1-A10, ...


1

My personal preferences: Stick to known-good algorithms like Shamir's Secret Sharing Scheme whose security properties are well-understood, rather than trying to invent something new. Reuse existing tools and formats/encodings, so you aren't dependent on something obscure or homemade that might not be maintained 10 years from now. Try to encode the seed ...


1

Create a 2 of 3 multisig wallet using electrum or copay. You'll get 3 seeds any 2 of which need to be used to spend your coins. Alternatively create a 2 of 4 multisig wallet. You can create any combination involving up to 15 co-signers. Here's a guide for electrum in case you are interested.


1

This can be scaled up to 24 word seeds just by continuing the pattern.


1

Have a look at byteball (http://byteball.org). It supports n-of-m wallets out of the box which can be used to implement a basic 2FA mechanism (2-of-2 with your desktop and your smartphone, for example.) It also has a chat mechanism built in, which can be used to communicate between the devices and which would probably enable you to do what you intend. ...


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