Emessbee: Construct Coinjoin Transactions Without a Coordinator

Super Testnet shared a proof-of-concept implementation of the Emessbee protocol for performing coinjoin transactions without a central coordinator.

Emessbee: Construct Coinjoin Transactions Without a Coordinator
  • The Emessbee protocol uses a 3-round serverless flow that can work with any 'public bulletin board' allowing for the sending and reading of messages.
  • The demo version of the protocol makes use of nostr as a public bulletin board for coordination, although the real version of the protocol would likely communicate over more secure channels.
  • "Emessbee also requires users to pay for their own block space. The mining fee is calculated after all change addresses are submitted, then divided up equally among all participants, and deducted from the amount that would otherwise go to users as change," added the developer.
  • According to the developer, the key advantages of the protocol are lack of coordinator and coordinator fees.
  • The developer also outlined a mechanism for reducing Denial-of-Service (DoS) attacks using 'The Kickout Protocol,' although it has not been implemented yet.
"I have not implemented this "kickout protocol" yet, so Emessbee is currently flawed: trolls can flood any attempt with fake messages to disrupt it and stop it from happening. But if Emessbee works in the happy path (it does) and if the kickout protocol can "enforce" the happy path, then I think we're in good shape," said Super Testnet.
  • Some also pointed out that the protocol also lacks Sybil-resistance mechanism, to which the developer responded that it is not a complete coinjoin software.
  • "After digging a bit the most interesting thing by far here is the use of ring signatures (like those leveraged in Monero) to prevent any mixing round participant from being able to deterministically link other participants inputs to outputs all without a central coordinator," commented Seth for Privacy.
"Perhaps I'm missing something, but this could be extremely useful for JoinMarket to implement! This enhances the Sybil resistance of fidelity bonds and also better protects makers against takers that attempt to reveal their outputs," he added.

Video demonstration:

Detailed presentation:

  • Slides of the presentation can be found here.

GitHub Repo
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