On Thu, Jul 08, 2021 at 08:48:14AM -0700, Jeremy wrote:
> This would disallow using a relative locktime and an absolute locktime
> for the same input. I don't think I've seen a use case for that so far,
> but ruling it out seems suboptimal.
> I think you meant disallowing a relative locktime and a sequence locktime? I
> agree it is suboptimal.
No? If you overload the nSequence for a per-input absolute locktime
(well in the past for eltoo), then you can't reuse the same input's
nSequence for a per-input relative locktime (ie CSV).
Apparently I have thought of a use for it now -- cut-through of PTLC
refunds when the timeout expires well after the channel settlement delay
has passed. (You want a signature that's valid after a relative locktime
of the delay and after the absolute timeout)
Ah -- I didn't mean a per input abs locktime, I mean the tx global locktime.
I agree that at some point we should just separate all locktime types per input so we get rid of all weirdness/overlap.
> What do you make of sequence tagged keys?
I think we want sequencing restrictions to be obvious from some (simple)
combination of nlocktime/nsequence/annex so that you don't have to
evaluate scripts/signatures in order to determine if a transaction
is final.
Perhaps there's a more general principle -- evaluating a script should
only return one bit of info: "bool tx_is_invalid_script_failed"; every
other bit of information -- how much is paid in fees (cf ethereum gas
calculations), when the tx is final, if the tx is only valid in some
chain fork, if other txs have to have already been mined / can't have
been mined, who loses funds and who gets funds, etc... -- should already
be obvious from a "simple" parsing of the tx.
Cheers,
aj
I don't think we have this property as is.
E.g. consider the transaction:
TX:
locktime: None
sequence: 100
scriptpubkey: 101 CSV
How will you tell it is able to be included without running the script?
I agree this is a useful property, but I don't think we can do it practically.
What's nice is the transaction in this form cannot go from invalid to valid -- once invalid it is always invalid for a given UTXO.
sequence tagged keys have this property -- a txn is either valid or invalid and that never changes w/o any external information needing to be passed up.