there a way to sig a message with multisig address?
if not, there a nice idea...
No, you don't sign with addresses. You sign with private keys.
It is possible to use multiple private keys to provide multiple signatures on a message. This is what a multisig address requires.
That's what multisigs are. They are created by signing with public keys.
No, you don't sign with public keys. You sign with private keys.
Multisig addresses are created by creating an output script that requires multiple signatures to be spent, and then hashing that script. The resulting hash is used to generate a P2SH address.
IIRC a public key (not public address) is used to make multisig in the same way an address is signed by creating a public key.
What?
Version 1 addresses aren't typically signed. Version 1 addresses are a Pay-to-PubKeyHash output script with a version number and a checksum. The resulting bytes are then converted to base58.
In other words a bitcoin public key can exist without being seen by the blockchain, while a multisig address doesn't exist until it's been seen by the blockchain.
A multisig address does not need to be seen by the blockchain in order to "exist". Why do you think that?
