> On 20 Dec 2018, at 6:09 AM, Christian Decker <decker.christ...@gmail.com> > wrote: > > Ruben Somsen via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org > <mailto:bitcoin-dev@lists.linuxfoundation.org>> > writes: > >> Hi Johnson, >> >> The design considerations here seem similar to the ML discussion of >> whether Graftroot should be optional [1]. >> >>> While this seems fully compatible with eltoo, is there any other proposals >>> require NOINPUT, and is adversely affected by either way of tagging? >> >> As far as I can tell it should be compatible with Statechains [2], >> since it pretty much mirrors Eltoo in setup. >> >> My understanding is somewhat lacking, so perhaps I am missing the >> mark, but it is not completely clear to me how this affects >> fungibility if taproot gets added and the setup and trigger tx for >> Eltoo get combined into a single transaction. Would the NOINPUT >> spending condition be hidden inside the taproot commitment? > > I'm not aware of a way to combine the setup and trigger transaction. The > trigger transaction was introduced in order to delay the start of the > timeouts until a later time, to avoid having an absolute lifetime limit > and having really huge timeout. If we were to combine the trigger > transaction with the setup transaction (which is broadcast during > channel creation), all of those timeouts would start counting down > immediately, and we could just skip the trigger transaction > altogether. It'd be more interesting to combine update and trigger > transactions in a sort of cut-through combination, but that doesn't seem > possible outside of Mimblewimble. > > Cheers, > Christian
Correct me if I’m wrong. For the sake of simplicity, in the following I assume BIP118, 143, and 141-P2WSH are used (i.e. no taproot). Also, I skipped all the possible optimisations. 1. A and B are going to setup a channel. 2. They create one setup tx, with a setup output of the following script: <s> CLTV DROP 2 Au Bu 2 CHECKMULTISIG. Do not sign 3. They create the update tx 0, spending the setup output with NOINPUT and locktime = s+1, to the update-0 output with the script: IF 2 As0 Bs0 2 CHECKMULTISIG ELSE <s+1> CLTV DROP 2 Au Bu 2 CHECKMULTISIG ENDIF 4. They create the settlement tx 0, spending the update-0 output with As0 and Bs0 using BIP68 relative-locktime, with 2 settlement outputs 5. They sign the setup tx and let it confirm 6. To update, they create the update tx 1, spending the setup output with NOINPUT and locktime = s+2, to the update-1 output with the script: IF 2 As1 Bs1 2 CHECKMULTISIG ELSE <s+2> CLTV DROP 2 Au Bu 2 CHECKMULTISIG ENDIF and create the settlement tx 1, spending the update-1 output with As1 and Bs1 using relative-locktime, with 2 settlement outputs 7. To close the channel, broadcast update tx 1. Wait for several confirmations. And broadcast settlement-tx-1
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