From rusty at rustcorp.com.au Fri Oct 12 06:36:57 2018 From: rusty at rustcorp.com.au (Rusty Russell) Date: Fri, 12 Oct 2018 17:06:57 +1030 Subject: [Lightning-dev] Commitment Transaction Format Update Proposals? In-Reply-To: References: <87in2769wc.fsf@rustcorp.com.au> Message-ID: <87woqn4qnq.fsf@rustcorp.com.au> ZmnSCPxj writes: > Good morning Rusty and list, > >> >> 1. Rather than trying to agree on what fees will be in the future, we >> should use an OP_TRUE-style output to allow CPFP (Roasbeef) >> > > My understanding is that this would require some base-layer changes at Bitcoin level first? At minimum IsStandard() modification, and I believe luke-jr suggested, to make a consensus rule that OP_TRUE would not be spendable beyond the block it appears in (i.e. it is used only for CPFP hooking) to reduce UTXO database size at lower layer. If you look further down, it's actually a P2WSH to "OP_TRUE". Wastes some space, but it works today. >> 3. The CLTV timeout should be symmetrical to avoid trying to game the >> peer into closing. (Connor IIRC?). > > I know this has been discussed before, but I wonder the rationale for the original asymmetric design, and the rationale for the new symmetric design. The original design does the minimum necessary (you *must* have a to-yourself delay to give time for the penalty tx to work). But, when combined with fee asymmetry (funder pays), it can lead the fundee to not care whether it forces the funder to perform a unilateral, or does a graceful mutual close. It's not a major issue, but aligning incentives (to mutual close) makes sense if we're changing other things I think. Cheers, Rusty.