Lets say someone was writing a transaction solely to denote the existence of something, or a timestamp, or writing something in OP_RETURN

Could that transaction be signed by other addresses, kind of as a "I agree with this statement" way, or a way that future analysis of that transaction showed that particular parties agreed with the transaction

(I'm imagining something that does not require the sender to have a multisignature address created with other parties. Or some way of having multiple outputs from different parties going to one input)

For example, Tom requested the location of Atlantis, many parties are watching these requests on the blockchain and can collaborate on the answer. Eventually Tom received a transaction containing the location in the OP_RETURN and it came from NOAA. Tom doesn't trust NOAA's use of GPS and much prefers GLONASS, so this transaction was also 'signed' or endorsed in some way by the Hydrometeorological Center of Russia. "Wow both agencies agree on this, I'm convinced now"

1 Answer 1


You could do something along those lines:

  1. Create a transaction to a multisig address with private keys that the different parties control.
  2. The parties sign a transaction having for input that multisig (which shows they agreed and signed) and for output the OP_RETURN.
  • interesting, but they would need to also reply to Tom in the proposed scenario, so then two outputs would be necessary? (I thought OP_RETURN can be extra data in an otherwise normal financial transaction between two parties)
    – CQM
    Aug 12, 2014 at 17:46
  • (in theory Tom could also listen for a reply, where Tom's question had 1 hash associated with it and the signed reply had the same hash)
    – CQM
    Aug 12, 2014 at 17:47
  • A problem with this solution is that the two institutions have no way of knowing they would both want to create a multisig address. But if they were listening to the question, they could both reply separately and the requestor could aggregate responses. Still a bit different from what I had in mind
    – CQM
    Aug 12, 2014 at 17:49
  • Been brainstorming this still: How about the initial institution makes their message in the OP_RETURN and the outputs include the addresses of other institutions that should also be able to answer/confirm the message. Then those institutions would be notified that either their presence is requested.
    – CQM
    Aug 13, 2014 at 4:39
  • ..... OR maybe Tom makes an output that notifies all those institutions, such as by referencing the OneName.io namespace on Namecoin, somehow. OR the first institution's response does that... ah, so many possibilities with so little understanding of how non-financial transactions can be formed
    – CQM
    Aug 13, 2014 at 4:47

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