rich1.0npub1zw7cc8z78v6s3grujfvcv3ckpvg6kr0w7nz9yzvwyglyg0qu5sjsqhkhpxhttps://nostr.ae/npub1zw7cc8z78v6s3grujfvcv3ckpvg6kr0w7nz9yzvwyglyg0qu5sjsqhkhpxnjumphttps://nostr.ae📅 Original date posted:2018-05-16 📝 Original message:Luke Dashjr <luke at dashjr.org> writes: > An OP_TRUE-only script with a low value seems like a good example of where the > weight doesn't reflect the true cost: it uses a UTXO forever, while only > costing a weight of 4. > > I like Johnson's idea to have some template (perhaps OP_2-only, to preserve > expected behaviour of OP_TRUE-only) that when combined with a 0-value is > always valid only if spent in the same block. > > I wonder if it would make sense to actually tie it to a transaction version > bit, such that when the bit is set, the transaction is serialised with +1 on > the output count and 00000000000000000181 is simply injected into the > transaction hashing... But for now, simply having a consensus rule that a bit > MUST be set for the expected behaviour, and the bit may ONLY be set when the > last output is exactly 00000000000000000181, would allow us to code the > transaction serialisation up later. (Maybe it should be the first output > instead of the last... Is there any legitimate reason one would have multiple > such dummy outputs?) Your zero-val-OP_TRUE-can't-be-spent-after-same-block SF is interesting, but if we want a SF just give us SIGHASH_NOINPUT and we'll not need this at all (though others still might). It's nicer than the previous discussions on after-the-fact feebumping[1] though. Meanwhile, our best mitigation against UTXO bloat is: 1. Make the fees as low as possible[2] 2. Put a CSV delay on the to-remote output (currently there's asymmetry) 3. Attach more value to the OP_TRUE output, say 1000 satoshi. But turns out we probably don't want an OP_TRUE output nor P2SH, because then the spending tx would be malleable. So P2WSH is is. This brings us another theoretical problem: someone could spend our OP_TRUE with a low-fee non-RBF tx, and we'd not be able to use it to CPFP the tx. It'd be hard to do, but possible. I think the network benefits from using OP_TRUE (anyone can clean, and size, vs some only-known-to-me pubkey) outweighs the risk, but it'd be nice if OP_TRUE P2WSH spends were always considered RBF. Thanks, Rusty. [1] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-April/015864.html [2] Because bitcoin core use legacy measurements, this is actually 253 satoshi per kilosipa for us, see https://github.com/ElementsProject/lightning/commit/2e687b9b352c9092b5e8bd4a688916ac50b44af0