Which ephemeral anchor script should lightning use?

[t-bast]

@harding

Reduction in reorg safety: a counterparty that works with a miner can pay the full value of a keyed anchor to their wallet, leaving both the commitment transaction and the CPFP transaction as zero fee in a block.

I hadn’t considered this case, thanks! I think this is fine though, because lightning nodes will only consider transactions irrevocably confirmed after a long enough delay to protect against reorgs. In this case, the honest node will keep rebroadcasting his anchor-spend (and the associated commitment), which honest miners should pick up?

HTLC delays should always be large enough to ensure that reorgs aren’t an issue (e.g. cltv_expiry_delta = 144 blocks) so this shouldn’t put funds at risk?

@harding

it may be possible for your counterparty to make good guesses about when your node will be offline for ~10 minutes.

While this may apply to small nodes (who probably aren’t a meaningful target since they’re small), I don’t think this applies to serious nodes (our node never has a 10 minutes downtime), so I think it could still be valuable to have the option to claim back some of the dust HTLCs instead of having them go entirely to fees? Even if you’re not able to claim it back 100% of the time, it’s still valuable if you’re able to claim it back sometimes?