On Wed, May 22, 2019 at 06:04:27AM +0000, ZmnSCPxj via bitcoin-dev wrote: > * I do not think CoinJoin is much improved by this opcode.
I think (especially with cross-input sig aggregation) it makes it easier to do a coinjoin during a high fee period -- if you're willing to wait 'til fees are lower to claim your funds you can still do that, despite participating now. Otherwise, I don't think it makes coordination that much easier. If the coinjoin groups stays around in a Layer 2-ish protocol, and coordinates to cut-through transactions, that could be a scaling and privacy benefit, but comes with much harder coordination problems. ie: A,B,C,D do a coinjoin with outputs of 1 BTC each tx on chain looks like: in: 1 A 1 B 1 C 1 D out: 4 to muSig(A,B,C,D) or COHV(1 A, 1 B, 1 C, 1 D) but then A wants to spend 0.2 BTC to E, and B wants to spend 0.1 BTC to F, so they agree to update the state and publish: in: (above, signed by A+B+C+D) out: 0.1 F 0.2 E 3.7 to muSig(A,B,C,D) or COHV(0.8 A, 0.9 B, 1 C, 1 D) and they continue the protocol. > * I cannot support replacing `SIGHASH_NOINPUT` with this opcode. (I don't think this in any way replaces ANYPREVOUT or similar) I think lightning is improved by this in that it makes it cheaper to create lightning channels during a high fee period. If you're creating 1000 channels you can do that via a single output with this opcode, and then wait until either there's a low fee period to publish the funding tx cheaply; or until the channel fails and you need to extract the funds which always has the risk of happening during a high fee period. You might be able to slightly simplify eltoo (or conceivably some parts of current lightning); if your eltoo update tx has as it's output [musig(A,B) or (n+1 cltv checksig) or (d CSV COHV(balances))] then your settlement transaction only needs to reveal the 40B script, rather than needing a 65B ANYPREVOUT signature. Cheers, aj _______________________________________________ bitcoin-dev mailing list firstname.lastname@example.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev