Multisig is orthogonal to the payment protocol (but payment protocol is
needed first).

There need to be protocols for:

a) Establishing multisig wallets of various sorts. See:
  https://moqups.com/gavinandresen/no8mzUDB/
  https://moqups.com/gavinandresen/no8mzUDB/p:ab18547e0
... etc.  for a UI mock-up.
  There needs to be some protocol so all participants in a multisig wallet
contribute keys (actually, we should just assume everybody uses BIP32 HD
public keys so we get privacy from the start).

Multi-person shared wallets, escrows, and "wallet protection service"
wallets (which might be protected with two-factor authentication) are
different use cases and probably use slightly different protocols (and will
probably need different BIPs eventually).


b) Gathering signatures for a multisig spend. Here is where the payment
protocol is useful; the PaymentRequest message should be passed around so
all participants know what is being paid for, and maybe a partially-signed
Payment message is where the signatures are gathered (or maybe the
signatures are sent separately and one of the participants creates and
submits the Payment and gets the PaymentACK... "to be designed").
  See:
    https://moqups.com/gavinandresen/no8mzUDB/p:a7e81be96
    https://moqups.com/gavinandresen/no8mzUDB/p:af7339204
... for UI mock-up for the multi-person-spend case.

And maybe a protocol for "I don't want to be part of this multisig any more
/ I lost control of my private key don't trust me in this multisig any
more".



On Mon, Mar 10, 2014 at 8:14 PM, Jeff Garzik <jgarzik@bitpay.com> wrote:

> All of that only melds with the payment protocol under an extremely
> expansive definition of "payment."  The payment protocol is really
> geared towards a direct one-to-one relationship....



>
>
--
Gavin Andresen