Bitcoin Forum

So let's say I make a 2 of 3 multi-sig.
So I have a total of 3 seeds and 3 zpubs.

Am I correct to say that I require at least 2 seeds and 1 zpub to be able to access the coins?

So if I lose one seed and its associated zpub, then I will lose the coins?

If I store the 3 seeds in a geographically distributed manner, the seed storage should be as follows?

Store seed    Store zpub
    1               2, 3
    2               1, 3
    3               1, 2

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Also, is there a mnemonic form for storing zpub? Seems pointless to have mnemonic for seed, but no mnemonic for zpub. Seems like both are equally important.

Yes. As long as the zpub doesn't corresponds to the 2 seeds you've stated.
Technically. Since your Multisig is generated with the list of public keys from those xpubs. However, if you can somehow figure out the redeem script of the address that the coins are in, you can still spend them. It is unlikely that you would be able to do so since the whole point is to discourage address reuse.
Yes.
No standard for those.

The method you have given is the most secure way to back up your multi-sig, but it does compromise your privacy somewhat since an attacker discovering one of your back ups will be able to see all your addresses and transactions (although not be able to spend any of your coins). There is another way you could back up your multi-sig as follows:

Back up 1: Seed A, Zpub B
Back up 2: Seed B, Zpub C
Back up 3: Seed C, Zpub A

If you use this scheme, then the compromise of any one of your back ups reveals nothing about your multi-sig wallet, but you still have all the information required to fully recover your wallet with any two shares.