Is your multisig compatible with other multisig solutions (Copay, Armory ...)? If yes, to what degree? Are there any standards for multisig?
We've added this to help you with that. http://cl.ly/image/0g2d3x1T3o0H/Detail%20View%3A%20Account%2...
Do Coinkite shared accounts interoperate with other vendors?
Although we are using the latest Bitcoin standards and technologies, it is hard to interoperate because of the following issues:
- Both parties need to correctly track all future and past P2SH addresses.
- Other "multisig" vendors are using P2SH and multisig in very limited ways.
- Most other vendors are keeping one private key to themselves, which prevents any useful interop.
- The BIP32 HD wallet paths are not well standardized.
- Any mistake or incompatibility can lead to lost funds and very bad karma.
However, to encourage progress in this area, we do include a "data export" option for one US-based exchange (Coinbase) and will add support for other vendors if it is useful. We also provide a one-click data export of all the details of the shared account, in our own simple JSON format.
We cannot provide technical support for individual end-users attempting to interoperate, but we are willing to speak to other vendors and support the greater crypto-currency community.
We list all UTXO for your account (with all the transaction hashes needed) in what we call the "audit report" and that includes multisig accounts now too. The subkey needed (M/x) is indicated in that report as well. Armed with that information, a site like ms-brainwallet can produce and send the transaction you need.
Also for you doomsday planning: we email a copy of the HSM private keys associated with your multisig account, encrypted with Coinkite master key that would be published after we shutdown. (Very similar to what we've always done with regular accounts).
Indeed, the multisig specification is currently incomplete since there is no a standard way to join wallets. Copay implements their own joining process (using websockets now, previously with WebRTC) while the bitcoin reference client doesn't have this "automated" capability.