Bitcoin Forum

Sorry newbie here so the terminology might be confusing.
Please correct me if I did not understand this correctly

Can I use multisig wallets to authorize two transactions at once?
The reason to do this would be to be me (M) and my transaction partner (P) to be our own escrow agent.

We could both deposit an amount A to a 2-2 multisig wallet (E)


M => E authorized by M
P => E authorized by P

Then after everything is ok, both parties could confirm the withdrawal of  to both parties' wallet

(
  E => M
  E => P
 )
authorized by M and P

Is such a setup possible?

This is one of the benefits of multisig wallet. It is 2-of-2 multisig. But make sure that you will give the cosigner public key and not private key or seed phrase. Also the cosigner should give you the public key and not private key or seed phrase. If you give yourselves private key or seed phrase, you defeat the purpose as the cosigners can also be able to make transaction successfully without depending on the other cosigner.

You can use Electrum for it. https://electrum.org/

There is only one transaction to sign by two co-signers.

With the 2-2 multisig wallet setup, there are two co-signers with same power and role. In your example, two cosigners are M and P, and a transaction A can be either broadcast by M or P.

If it is initiated by M, P will check it, sign it to finalize the transaction to Bitcoin mempools.
If it is initiated by P, M will check it, sign it to finalize the transaction to Bitcoin mempools.

Creating a multisig wallet (https://bitcoinelectrum.com/creating-a-multisig-wallet/)
How does a multisig wallet work? (https://bitcoinmagazine.com/guides/what-is-a-multisignature-wallet)

Technically you cannot sign both partial transactions at the same time. Multisig co-signing is not an atomic operation because it is designed to be done non-interactively, that is you sign first and then you give the partial transaction to your friend who signs with the other key.