It’s not clear for me how a collaborative exit works, in particular how atomicity is achieved.

I would assume the ASP will fund an on-chain transaction, paying to Alice, in return for a VTXO forfeit from Alice.

  1. Will the payment to Alice be an additional output on the next pool transaction or a new transaction?

  2. How atomicity is achieved if it is a new transaction? Does it also use a connector from the new pool transaction?

1 Answer 1


The collaborative exit is very similar to a regular in-Ark transaction. Instead of swapping your vtxo for another vtxo in the new vtxo tree, you swap your vtxo for an actual output on the Ark round tx. You will obviously have to pay some more fees for this type of transaction, but the atomicity works in exactly the same way: through the connector output that you use as an input to your forfeit tx.

In the diagram below, Alice is "lifting" her vtxo A* out of the Ark into output A_out.

enter image description here

  • 1
    Clarification: what you called the Ark tx is what I called the Pool tx, right?
    – bordalix
    Commented Oct 12, 2023 at 14:51
  • Exactly, yeah. The transaction that is the result of an Ark round. Yeah "Ark tx" is probably a bad name because that's what in-Ark txs could also be called. Maybe "Ark round tx" would make sense. I don't think "pool" is the right word; in Bitcoin, pools usually indicate collaborative custody, which is not the case in Ark. In Ark there is no collaboration between users at all, the ASP is basically a middleman between all txs. Commented Oct 13, 2023 at 10:25
  • 1
    Yeah, we really need to work on nomenclature: onboarding vs lifting, round tx vs pool tx, funding tx vs lifting tx, etc.
    – bordalix
    Commented Oct 13, 2023 at 16:50

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