RBF fee bump payment transactions about walletwasabi HOT 5 OPEN

In case there is enough change, RBF is really easy to implement -> Just reduce change

If there is not enough change, there are 4 possibilities:

• Wallet has other private/same pocket coins bigger than some selected so swapping some selected coins with other could be enough to cover the fee -> only downside is potentially (more) change
• Wallet has other private/same pocket coins smaller than the selected ones, some inputs can be added to cover for the extra fee -> it will increase size of the TX + potentially create (more) change
• Amount sent can be reduced to cover for the extra fee -> best solution but causes issues for payments.
• An extra non private output from another pocket -> degrades privacy, increases size of the TX and potentially create (more) change

In all cases it's probably better to just re-run the automatic coin selector but making sure that old TX will be replaced by the new one. One remaining question: If these are the only possible outcomes, should the user have an actionnable choice whether he wants to degrade his privacy by adding another pocket, have change, or reduce the amount?

from walletwasabi.

@turbolay

From the point of view of simplicity, I'd recommend that the original transaction inputs always be kept when RBF fee bumping. You don't want to accidentally create two distinct transactions, eg by selecting a different input to keep in different, successive, fee bumps. Better to lose a bit of privacy for the first version of this feature than accidentally create a double-payment bug.

from walletwasabi.

The effective fee rate calculation gets difficult if there is a chain of unconfirmed transactions prior to the users transaction.

This shouldn't be a problem if we are doing this for only single user transactions that are initiated from the users wallet (user has all inputs).

from walletwasabi.

the UX should warn the user about the privacy downsides [change output detection and potential additional non-private inputs]

from walletwasabi.

The effective fee rate calculation gets difficult if there is a chain of unconfirmed transactions prior to the users transaction.

from walletwasabi.