Yes I believe this is async payment based on this definition (used in Lightning context): https://bitcoinops.org/en/topics/async-payments/ .
It's not fully trustless though.
Which party is trusted? The sender, the recipient, or someone else?
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Yeah, that's a good question. I don't know how to answer that well. If we are using "trustless" as "NOT trusting any third party outside of Alice and Bob", then I guess it's trustless? But I think the highlight is that Alice can scam Bob in couple ways and Bob may miss on receiving some sats he would otherwise get if we didn't have the "pull back after 2 weeks" clause. This is comparable situation to other schemes, but onchain finality is better experience.
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I think the highlight is that Alice can scam Bob in couple ways
How?
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On further thought I think my comment was not useful, so feel free to disregard.
What I meant is that the usual social tricks that apply to other solutions apply here too. As soon as you have a setup where money can be "clawed back" later, that opens multiple scam opportunities.
  • Alice pays bob in person in some physical corner store, Bob has static address displayed. Alice pays, shows nice checkmark that she paid, Bob believes her and gives the produce in return. Bob doesn't claim the sats for 2 weeks because he's not technical. Alice reverts the payment. Bob notices a week after that and feels scammed.
  • Alice can create scam scheme where she uses a visual proof of payment to gain social engineering leverage over Bob. Most of current "fake microsoft phone support center for seniors" scams are based on this. They make you believe that they accidentally send you extra money and ask you to return it. But you never actually received the money in the first place.
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Alice can do this a lot easier by screenshotting a green checkmark and showing that to Bob
In person merchants need to, and easily can, check their own device immediately. In doing so, it can automatically secure the funds permanently against Alice's pullback by withdrawing to a "real" lightning wallet
Hedgehog is more for situations like online payments and zaps where the recipient might not get online for a few days. Once you do it should automatically secure your funds. And if you don't get the money for two weeks I am of the opinion Alice should have an opportunity to recover it
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