From aj at erisian.com.au  Tue Oct 12 04:48:56 2021
From: aj at erisian.com.au (Anthony Towns)
Date: Tue, 12 Oct 2021 14:48:56 +1000
Subject: [Lightning-dev] Lightning over taproot with PTLCs
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On Tue, Oct 12, 2021 at 04:18:37AM +0000, ZmnSCPxj via Lightning-dev wrote:
> > A+P + max(0, B'-B)*0.1 to Alice
> > B-f - max(0, B'-B)*0.1 to Bob

> So, if what you propose is widespread, then a theft attempt is costless: 

That's what the "max" part prevents -- if your current balance is B and
you try to claim an old state with B' > B for a profit of B'-B, Alice
will instead take 10% of that value.

(Except maybe all the funds they were trying to steal were in P' rather
than B'; so better might have been "A+P + max(0, min(B'+P'-B)*0.1, B)")

Eltoo would enable costless theft attempts (ignoring fees), particularly
for multiparty channels/factories, of course, so getting the game theory
right in advance of that seems worth the effort anyway.

Cheers,
aj