Super Testnet13d agoA layer two (aka "second layer") is a service where users can send their bitcoins and then transact on the service with reduced impact on bitcoin's blockchain, where users can withdraw their bitcoins by getting one or more bitcoin transactions confirmed. It is not a second layer if, without changing bitcoin's consensus rules or using a 51% mining attack, a group of one or more third parties, and/or the service itself, can render any user's ability to withdraw invalid.
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waxwing13d agoInteresting. If we think of LN, we have that: not only ability to withdraw, but also ability to maintain currently held funds, passively, can be violated even without 51% attack but merely through censorship by miners, or even pure unavailability or pricing out through fees > available balance. Hence someone put it in some pithy statement that I can't remember along the lines of "in Lightning censorship resistance is a security requirement" (meh I can't remember exactly but you get it). But then is that overlapping with a 51% attack, or not? I always thought of the latter as specifically referring to attempts to "undo" payments, so changing inclusion and/or ordering of txs. I think I'm trying to say that, with this definition, even LN doesn't count as an L2, does it?
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Super Testnet13d agoIn my mind, a lightning withdrawal that pays sufficient fees can only be censored if a sufficiently large group of "anti-withdrawal" miners collude to reject it. If the anti-withdrawal miners have less than 99.9% hashrate, then, given that, per the LN protocol, there are 2016 blocks to mine the withdrawal tx, there is a good chance the remaining miners (0.1% or more) will mine it. And at that point, miners have to perform a 51% attack to "undo" it.
But I suppose, if you define "merely refusing to mine it" as different from a 51% attack, my definition does allow an edge case where, if 99.999% of hashrate consists of anti-withdrawal miners, then even if they won't perform a 51% attack, you're still unlikely to get your withdrawal transaction mined, because too few miners are "on your side" -- the ones who are, are unlikely to find a block in LN's 2016 justice window.
But even in that edge case, I think my definition still works: I carefully chose the phrase "render...invalid" so that it would call to mind transaction validity. Your transaction would not be invalid just because 99.999% of miners refuse to mine it. If the withdrawal transaction(s) remain valid, the service still counts as a layer two, even if most miners refuse to mine it.
One might wonder if that also means my definition can be shortened by removing the reference to a 51% attack, since, by most definitions, a transaction is not rendered invalid just because miners attack it with a 51% attack. But I think the reference is still useful, because in the case of lightning, the justice tx competes with the finalization tx to spend the same input, and so, if a 51% attack causes the finalization tx to get sufficient confirmations before the justice tx can get them, then the justice tx is actually rendered invalid -- because it tries to spend an input that has already been spent.
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Brunswick13d agoYes, that is why liquid, as useful as it may be, is not a layer 2, and ecash is not a layer 3. Ecash is a custodial lightning service.
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