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I want to use message signing to prove control of a multi signature Bitcoin address. Is it possible? In theory it must be. In practice, are there any Bitcoin wallets that allow this? Specifically, how can I do this with Armory Lockboxes?

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Signing message is proof of ownership of private key

Multisignature/P2SH address is hash of several (including zero) public keys

So, signing message with M private keys and disclosing the "contents" of msig address M-of-N is proof of control on address.

I do not know are there existing services to sign/verify p2sh addresses, but it is possible. Do not know about Armory/others.

  • Yes. You would need to disclose public keys and provide signed messages with them. There must be a way in theory to do that without disclosing the public keys. It's actually no different than creating a signed transaction. Is it not? – Emre Kenci Dec 1 '14 at 9:49
  • It is not possible (by default) to get public keys from p2sh-address, so all public keys and their order must be known for verification. – amaclin Dec 1 '14 at 9:57
  • But can we still verify the signature without knowing the public keys and their order? Is it not the same with verification of transaction signatures? – Emre Kenci Dec 1 '14 at 10:03
  • ECDSA verification requires public keys. It is not possible to verify signature without knowledge of public key. It is nonsense to verify message by signature only - no proof of anything. – amaclin Dec 1 '14 at 10:08
  • Ok Thanks. Bear with me for a little while longer :) Does this mean that everytime you broadcast a multi sig transaction you are disclosing the public keys and their order? – Emre Kenci Dec 1 '14 at 10:20

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