That is attainable with each output sort apart from P2TR. Taproot launched to the Bitcoin protocol Schnorr signatures and Merklized Various Script Bushes, each of which can be utilized to cover the true variety of contributors in a multisig.

Schnorr signatures

Taproot makes use of a brand new signature scheme referred to as Schnorr signatures, which permits key aggregation. A single public key can belong to at least one person or be aggregated from a number of customers utilizing an n-of-n scheme like MuSig2 or perhaps a threshold m-of-n scheme like FROST/ROAST. This makes multisig transactions smaller and subsequently cheaper, but it surely additionally means you can’t inform if a multisig even occurred, not to mention its measurement.

Merklized Various Script Bushes

A P2TR output can optionally decide to a script tree (MAST). The important thing distinction from earlier output sorts is which you could now have many different spending circumstances, and solely reveal the one which you find yourself utilizing.

Even with out key aggregation, this lets you obfuscate the precise measurement of your multisig. For instance, if you would like a 2-of-3 multisig, you’ll be able to create a script tree with three totally different 2-of-2 multisigs: A&B, B&C and A&C. Solely considered one of these 2-of-2s will have to be revealed and no one will be capable of inform if the precise multisig was 2-of-2, 2-of-n for some larger n, or perhaps a decoy multisig wherein each keys have been in truth owned by the identical particular person.

You should use key aggregation together with script bushes, for instance to implement 2-of-3 utilizing three totally different keys aggregated utilizing 2-of-2 MuSig2. A footnote in BIP342 goes right into a little bit of element on multisigs in script bushes.