Two Questions About Multisignatures

[butka]

I'm a total beginner when it comes to multisig addresses and wallets, so I would appreciate some help from the community.

1. I know that you can make a P2SH (pay to script hash) address that can be redeemed by a multisig script. But can you create a multisig wallet for P2PKH addresses? 

I see that Electrum has this option (it asks for standard vs Segwit multisig wallet). It is somehow not clear to me how the output script is redeemed in the first case, as we have to have a hash of a multisig script, not a hash of a public key.

2. Second, I wasn't able to find a decisive answer, so probably what I'm suggesting is not possible. But it won't hurt to ask.

Let's say I want to make a multisig 2 of 3. Is there a way to make one of the signatures mandatory?

This would be convenient in hypothetical situations like the following. Let's say the money belongs to me, but I want to involve other people (to possibly improve security) so I create a multisig address 2 of 3:

• the 1st key is held by me
• the 2nd key is held by a relative
• the 3rd key is held by a friend.

If the first key is mandatory, my relative and my friend cannot conspire against me and steal my money.

Is there a place in the redeem script for complex logic that is probably needed to define what keys are optional and what mandatory?

After some consideration, it occurred to me that what I'm trying to achieve can be done by a 3 out of 4 multisig:

• the 1st key is held by me
• the 2nd key is held by me
• the 3rd key is held by a relative
• the 4th key is held by a friend.

so the dilemma is solved, but still the question remains, can there be a mandatory signature in a multisig solution?

Thanks in advance and sorry if some of these questions are dumb or obvious.

[1713243186]

1713243186

[TryNinja]

AFAIK it's not possible. You'll need to use the 3-of-4 scheme.

[ranochigo]

1. I know that you can make a P2SH (pay to script hash) address that can be redeemed by a multisig script. But can you create a multisig wallet for P2PKH addresses? 

No. P2PKH addresses (prefix of 1) doesn't allow the creator of the address to set a pre-defined condition. P2SH has scripts which allows the creator to set conditions for the outputs to be spent. The only thing that restricts P2PKH is to have a valid signature.

2. Second, I wasn't able to find a decisive answer, so probably what I'm suggesting is not possible. But it won't hurt to ask.

Let's say I want to make a multisig 2 of 3. Is there a way to make one of the signatures mandatory?

Yes. IIRC, one of the post on Bitcointalk was on this and it was possible in theory. I vaguely remember that it was years ago and I forgot all the technical details about it. I'll have to search my post history for a bit.

[Abdussamad]

so the dilemma is solved, but still the question remains, can there be a mandatory signature in a multisig solution?

Any thing that you can code with the bitcoin script language can be turned into a p2sh address. Smart contracts and such for example. However no wallet supports such solutions out of the box right now so while it's possible it's out of the reach of lay persons.

[butka]

No. P2PKH addresses (prefix of 1) doesn't allow the creator of the address to set a pre-defined condition. P2SH has scripts which allows the creator to set conditions for the outputs to be spent. The only thing that restricts P2PKH is to have a valid signature.

Any thing that you can code with the bitcoin script language can be turned into a p2sh address.

I see, thanks for clearing this up. So P2SH addresses are the ones that actually enable complex scripting necessary for multisignatures.

However no wallet supports such solutions out of the box right now so while it's possible it's out of the reach of lay persons.

So better to stick to mutlisig wallets. Just a thought. Given that some opcodes are disabled on the Bitcoin network, it could still happen that a complex script made by hand isn't currently redeemable after all.

To summarize point 2, in practice, the 3 of 4 wallet could be an easy solution.

Thank you all for your replies.

[twthmoses]

To summarize point 2, in practice, the 3 of 4 wallet could be an easy solution.

Thank you all for your replies.

A very nice and easy solution, 3 out of 4, of which you own two of them. I guess that should work as you would like it to. You would always be a required signer.