rich1.0npub1g5zswf6y48f7fy90jf3tlcuwdmjn8znhzaa4vkmtxaeskca8hpss23ms3lhttps://nostr.ae/npub1g5zswf6y48f7fy90jf3tlcuwdmjn8znhzaa4vkmtxaeskca8hpss23ms3lnjumphttps://nostr.ae📅 Original date posted:2019-12-17 📝 Original message: Good morning t-bast, Further, we can enforce that RBF is signalled for every spend of the output by: <0> OP_CHECKSEQUENCEVERIFY OP_DROP <R> OP_SWAP OP_CAT <ACINQ> OP_CHECKSIG Requiring that RBF is signalled gives a little more assurance. Suppose ACINQ becomes evil and double-spends the output. The transaction that is posted in the mempool must be marked by RBF due to the `OP_CHECKSEQUENCEVERIFY` opcode, since `nSequence` also doubles as RBF opt-in. Then anyone who notices the double-spend can RBF the double-spending transaction to themselves rather than ACINQ. This also further publishes ACINQ private key, until the winning transaction has an `OP_RETURN` output that pays the entire value as fees and nobody can RBF it further. This is a minor increase in the assurability of the construction, by making any output that is double-spent directly revocable in favor of the miners. Again, it requires `OP_CAT`, which is a very dangerous opcode, allowing such powerful constructions. Regards, ZmnSCPxj > Thanks a lot David for the suggestion and pointers, that's a really interesting solution. > I will dive into that in-depth, it could be very useful for many layer-2 constructions. > > Thanks ZmnSCPxj as well for the quick feedback and the `OP_CAT` construction, > a lot of cool tricks coming up once (if?) we have such tools in the future ;) > > Le mar. 17 déc. 2019 à 16:14, ZmnSCPxj <ZmnSCPxj at protonmail.com> a écrit : > > > Good morning David, t-bast, and all, > > > > > I'm not aware of any way to currently force single-show signatures in > > > Bitcoin, so this is pretty theoretical. Also, single-show signatures > > > add a lot of fragility to any setup and make useful features like RBF > > > fee bumping unavailable. > > > > With `OP_CAT`, we can enforce that a particular `R` is used, which allows to implement single-show signatures. > > > >     # Assuming signatures are the concatenation of (R,s) > >     <R> OP_SWAP OP_CAT <ACINQ> OP_CHECKSIG > > > > The above would then feed `s` only on the witness stack. > > > > Regards, > > ZmnSCPxj