Please help How do I sign multisig transactions through Electrum Wallet

[platinumsteel2016]

I have manage to understand and retrieve my Master Public Key, but I am confused about
How to sign multisig transactions part of the process.  I have the latest version of Electrum Wallet for laptop.
Please help me to understand this procedure (layman terms please)! Is there possibly a current Youtube video,
though I couldn't find one that was current.

Hoping to hear from you reasonably soon.

[BrewMaster]

the safest way which would also require a lot less hassle is to creat a new wallet and select the "Multi-signature wallet" option and then import your master private keys for the keys you have and want to sign with and master public keys for the keys you don't have but must exist to create the correct addresses.
then you can easily spend the coins using the UI like you'd do any other coin.

if you want to learn the technical part and know what's happening under the hood that is a different story.

[icopress]

If you take a look at this step-by-step guide ^{[Electrum Guide]}, you can easily figure out the details of the entire process, (If you are looking for security or joint control of BTC, then be sure to take literally a few minutes to find out more). Good luck with your endeavor. 

This tutorial shows how to create a 2 of 2 multisig wallet. A 2 of 2 multisig consists of 2 separate wallets (usually on separate machines and potentially controlled by separate people) that have to be used in conjunction in order to access the funds. Both wallets have the same set of Addresses.

[Dabs]

I would recommend you make a 2-of-3 as that is the one most likely you'll end up using. 2-of-3 also allows to have 1 backup master private key (or seed) in case you lose one. 1 key you have on you or your mobile wallet, 1 key you have on a laptop or computer, and 1 key just kept safe. You will need the public keys of all of them.

[pooya87]

I would recommend you make a 2-of-3 as that is the one most likely you'll end up using. 2-of-3 also allows to have 1 backup master private key (or seed) in case you lose one. 1 key you have on you or your mobile wallet, 1 key you have on a laptop or computer, and 1 key just kept safe. You will need the public keys of all of them.

You should also add that using a multi-signature scheme will increase the signature and the transaction size (since the tx now requires 2 signatures instead of 1 and a big redeem script containing 3 public keys instead of 1) and that increases the amount of fee the user has to pay for each transaction.
In other words the additional security comes at a big cost.

[nc50lc]

-snip- but I am confused about
How to sign multisig transactions part of the process.  I have the latest version of Electrum Wallet for laptop.

Hope this is good enough:

• 1. Go to "Tools->Preferences->Transactions" tab and check if "advanced preview" is ticked.
• 2-A. (if advance preview is disabled) Create a transaction in either one of the wallets, click "pay", then set the fee, clicking send in the 'confirm transaction' window will automatically open 'advanced preview' whether it's enabled or not; it's automatically signed after you clicked "send" and typed your password.
• 2-B. (if advance preview is enabled) Create a transaction in either one of the wallets, after clicking "pay" in the 'send' tab, the advanced preview will be displayed. Change what you want to change in the transaction then click "finalize", in the next window, click "sign" and type your password.
• 3. After either 2-A or 2-B, click "Export" then "Copy to Clipboard" or "Export to file". You can now save it locally and/or directly close the window.
• 4. In the other Electrum wallets (cosigners), click "Tools" then "Load transaction", select "From File" if you want to load the file created by "export to file" in the previous step, or "From text" to be able to paste what's been copied by "Copy to Clipboard" in the previous step.
• 5. An advance preview will open and you only need to click "sign" (type your password), if it needs more than two signatures, "export" again and pass the new signed transaction to the next cosigner.
  Do not use the previously exported file/text, you need to export (same as step 3) the loaded and signed transaction. "broadcast" next to "sign" button will be available after having enough signatures.
• 6. Lastly, once "broadcast" is clickable, use it and the transaction will be sent to the network.

[Dabs]

You should also add that using a multi-signature scheme will increase the signature and the transaction size (since the tx now requires 2 signatures instead of 1 and a big redeem script containing 3 public keys instead of 1) and that increases the amount of fee the user has to pay for each transaction.
In other words the additional security comes at a big cost.

That is true, until Electrum implements taproot/schnor signatures. They are supposed to combine plenty of sigs into one, so a multi-sig with 3-of-5 with 3 sigs will look like 1 sig and cost the same as 1 sig. Hopefully that comes soon, and when it does, plenty more will be using multi-sig.

[dkbit98]

That is true, until Electrum implements taproot/schnor signatures. They are supposed to combine plenty of sigs into one, so a multi-sig with 3-of-5 with 3 sigs will look like 1 sig and cost the same as 1 sig. Hopefully that comes soon, and when it does, plenty more will be using multi-sig.

It is also a question how long it will take for Electrum and other wallets to implement those changes after Taproot activation, but I know that GreenWallet by Blockstream is working on MuSig2 Simple Two-Round Schnorr Multisignatures with non-interactive signing, that sounds interesting in theory.
I am not always a fan of things that Blockstream is doing but this might be the good thing.

[pooya87]

It is also a question how long it will take for Electrum and other wallets to implement those changes after Taproot activation, but I know that GreenWallet by Blockstream is working on MuSig2 Simple Two-Round Schnorr Multisignatures with non-interactive signing, that sounds interesting in theory.
I am not always a fan of things that Blockstream is doing but this might be the good thing.

Considering the fact that Electrum was one of the first wallets to implement SegWit back in 2017, I would say they are going to be one of the first to implement Taproot and Schnorr signatures too. Specially since Electrum has been using libsec256k1 (same library that bitcoin core uses) for some time now the workload is significantly reduced.