LN-Symmetry Project Recap

[instagibbs]

@ProofOfKeags

Can you elaborate on precisely why this is the case. I’m not sure I intuit why this is necessary. In theory the injunction period in the existing protocol is two rounds max: breach and justice. In eltoo, my understanding is that it is still two rounds: breach and fast-forward.

Fairly simple to explain and obvious in retrospect:

1. Alice and Bob do some channel ops
2. Alice then sends update_signed which is a MuSig2 partial sig
3. Bob smirks now that he’s the only one with the full signature, goes silent
4. Alice goes to chain with prior state, waits however long the “update phase” has a timelock for the “settle transaction” to be valid
5. Right before timelock expires, Bob publishes the final state
6. wait for this timelock to expire… publish settle tx
7. finally can settle HTLCs

that’s 2x the update phase timelock, not 1x. I know there’s some “sandwiching” you can do to compress it a bit(conversations between LN engineers I didn’t understand!), but it’s north of my once expected 1x.

This game also shows up in the “layered eltoo” design from [Lightning-dev] Layered commitments with eltoo which was supposed to get rid of the additional delta values altogether.

@ProofOfKeags

I’m thoroughly unsurprised by this as CTV/Covenant schemes can, in principle, give you state-graph cut-through on any state machine encoded into Bitcoin transactions. However, I do have a question as to whether alternative covenant schemes also give you this property? I suspect but am not certain that they can.

OP_CTV is probably the ideal here? I never validated it end to end or carefully looked though. I emulated it for a few more vbytes using APO.