Do we need all 3 master public keys in 2 of 3 multisig wallet ?

[new19980]

Hello i have question about multisig wallet according to what i understand is that if i created
a 2 of 3 multisig wallet then i just need to save two seed / private keys to sign transactions and recover the wallet right ?
but i heard some peoples saying that we need all of the 3 public keys and derivation path to restore the wallet why do we need
all of the 3 public keys to restore the wallet when only 2 private keys are able to sign transactions and if i lost one of the three
public keys does that mean that my BTC is gone and cant restore with only 2 seed and two public master keys ?

[Charles-Tim]

Yes, you can not recover the wallet with 2 keys. You need the 3 private keys to restore the wallet. Everything you posted is correct. After you set up the wallet, just 2 keys are needed for making transactions, but to set up the wallet again like during recovery, you need the 3 keys.

[new19980]

Yes, you can not recover the wallet with 2 keys. You need the 3 private keys to restore the wallet. Everything you posted is correct. After you set up the wallet, just 2 keys are need for making transactions, but for to set up the wallet again you need the 3 keys.

Thnx but what about public master keys why do we need all of 3 ? or to restore the wallet we need 3 seed / private keys + 3 public master keys + 3 derivation paths

[hugeblack]

With two keys in 2 of 3 multisig wallet, you can sign the transaction and send it to a new wallet (whose seed/private-key you have), so with two keys you can indirectly access the private key by sending your balance to a new address but you will not be able to recover the old wallet.

[dkbit98]

Hello i have question about multisig wallet according to what i understand is that if i created
a 2 of 3 multisig wallet then i just need to save two seed / private keys to sign transactions and recover the wallet right ?

Can you tell us why do you want to create multisig setup?
This adds additional complication and you will have to pay more fees for transaction when you recover your seed phrase.
Generally I don't suggest newbies to use multisig setup unless they have very large amount of bitcoin to protect and share with someone else.

if i lost one of the three
public keys does that mean that my BTC is gone and cant restore with only 2 seed and two public master keys ?

No.
Maybe you should consider using SLIP39 instead of multisig setup.

[Knight Hider]

Thnx but what about public master keys why do we need all of 3 ? or to restore the wallet we need 3 seed / private keys + 3 public master keys + 3 derivation paths

To sign a transaction from a 2 of 3 multisig, you need: 2 private keys and the third public key. You can store all public keys with each private key so you have all details with 2 parts.

[new19980]

Can you tell us why do you want to create multisig setup?

Because i think its much secure than standard wallet even if its created on airgap computer there is a chance
of a malware infection when you connect a usb flash drive to sign transactions so my plan is to open a multisig wallets
on electrum directly without any hardware wallets and sign transactions from multiple offline laptops

you will have to pay more fees for transaction when you recover your seed phrase.

what do u mean by this does recovering or restoring the wallet with the seed need transaction fees to pay ? why i have to pay more fees?

[MusaMohamed]

Creating a multisig wallet.

When you want to sign a transaction from a multisig wallet, for example 2/3 cosigner multisig wallet, you will need 2 cosigners to sign that transaction for spending bitcoin.

To recover that multisig wallet, you will need all 3 Master Public Keys from 2 cosigners, one from you and two from 2 other cosigners.

Spending: 2 cosigners is enough.
Recovery: 3 cosigners is mandatory.

[new19980]

Creating a multisig wallet.

When you want to sign a transaction from a multisig wallet, for example 2/3 cosigner multisig wallet, you will need 2 cosigners to sign that transaction for spending bitcoin.

To recover that multisig wallet, you will need all 3 Master Public Keys from 2 cosigners, one from you and two from 2 other cosigners.

Spending: 2 cosigners is enough.
Recovery: 3 cosigners is mandatory.

Thnx so for recovering i need all of 3 public keys and 3 seed / private keys or just two seed are enouph?

[dkbit98]

Because i think its much secure than standard wallet even if its created on airgap computer there is a chance
of a malware infection

Sorry, but you don't know what you are talking about, and there is a good chance you could lose your coins with multisig.
If you are the single person creating a multisig there is a good chance you will mess something up and lose your coins.

what do u mean by this does recovering or restoring the wallet with the seed need transaction fees to pay ? why i have to pay more fees?

Dude... you have to make multiple blockchain transactions every time you are making any transaction or restoring seed phrases.
Multisig setup is mostly used for companies or group of people with lot of coins.
It should not be used as protection from malware.

[Cricktor]

In a n-of-m multisig setup (usually n is smaller than m, but could be equal) you need:

• all m public keys¹ to get public addresses of the wallet
• at minimum n private keys plus m-n public keys to sign a transaction to move coins from the wallet (without the sum of m keys you can't create the unlock script to move coins)

¹Remember that you can always get a public key from a private key.

I can't emphasize this enough should you not understand multisig completely: you can't afford to loose any one key completely! This may surprise you. Before you object, I invite you to think about it a bit more in depth.

Let's take the example of a simple 2-of-3 multisig. When we speak of private key or public key, let's assume it's the extended private or public key from which you can derive the individual private and public keys as needed by derivation path down to single keys.

• you have all three private keys: no-brainer, any public key can be derived, you can sign with any combination of two distinct private keys and the other third public key
• you have two distinct private keys and the third public key which is not one of the public keys from your private keys: you can derive public addresses of your wallet and you can sign transactions from your wallet
• you have one private key and the two other public keys: you can derive public addresses of your wallet, but you can't sign transactions because you only have one private key where you would need two of them
• you have three public keys: you can have a safe watch-only wallet which can derive all public addresses of the wallet but not more
• you have only two distinct keys, doesn't matter if private or public: you're screwed, because you can't create any address of your wallet and therefore you can't also sign a transaction even with two distinct private keys
• anything less than the step before isn't any better: you're screwed anyway

[nakamura12]

Creating a multisig wallet.

When you want to sign a transaction from a multisig wallet, for example 2/3 cosigner multisig wallet, you will need 2 cosigners to sign that transaction for spending bitcoin.

To recover that multisig wallet, you will need all 3 Master Public Keys from 2 cosigners, one from you and two from 2 other cosigners.

Spending: 2 cosigners is enough.
Recovery: 3 cosigners is mandatory.

Thnx so for recovering i need all of 3 public keys and 3 seed / private keys or just two seed are enouph?

You will need the three private keys to setup the wallet again which is mandatory or you cannot set it up. You cannot access the wallet without it but for making transactions like sending bitcoin to another wallet is you can do it with just to keys. Using a wallet that is not multi sig is safe enough if you know how to keep your security measures so it's better if you don't use multi sig wallet. Multi sig as the name goes is good for more than one person to manage like in a company or have lots of bitcoin.

[nc50lc]

-snip- does that mean that my BTC is gone and cant restore with only 2 seed and two public master keys ?

To understand this better, here's how it works under the hood:
Your MultiSig addresses are actually 'ScriptPubKeys' hashed from the "Redeem Scripts" created from public keys derived from those three cosigners' (master) extended private key.
Your redeem scripts look like this (for 2-of-3 MultiSig): OP2 <pubKey1> <pubKey2> <pubKey3> OP_3 OP_CHECKMULTISIG and that is required to spend the outputs locked with it.
As you can see, it requires all three cosigner's pubKeys.

The only way to recover your BTC in case you're missing one backup is if a particular funded address is used to send at least once (reused).
So you can do a workaround of using its revealed redeem script to manually create a transaction to sign with your 2 available private keys.