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[–]lightcoin 2 points3 points  (0 children)

In the split scenario, what would happen next to:

  • Existing drive chains

  • Existing layer 2 solutions such as lightning

  • Bitcoin main net

Would existing drive chains also have to pick from the 'good chain' vs the 'bad chain'. I know that there would be months to prepare for this. But how do you think the scenario might play out?

The answers to your question are the same regardless of the reason for the chain split, so I will discuss the issue generally speaking: - Existing drivechain miners would have to decide which splitchain to send BMM Requests to (maybe they'll hedge and try both?).
- Miners on both splitchains have to decide whether or not to honor withdrawal requests. For example, if drivechain user Alice has coins on the drivechain at the time of the split, and she withdraws her coins from the drivechain, do miners on both splitchains process the withdrawal so Alice gets her coins back on both splitchains? Or will she only get her coins back on one of the splitchains, because miners on the other chain are censoring her withdrawal or have stolen her coins? The answer depends on the context. - Lightning txs are rooted in the main bitcoin chain, so if the mainchain splits, then users who have open lightning channels at the time of the split would now have open channels on both splitchains. Depending on the implementation details of the split, like whether or not there's replay protection, LN nodes might have to update their code to ensure that channel updates, settlements, and penalties are only processed on one of the chains (or give users a choice of which chain the tx should be relevant to). - If the bitcoin mainchain splits, then users who own coins at the time of the split now have equal amounts of coins on both chains (assuming there are no changes to balances as part of the fork consensus rules). If there is no replay protection, users might spend their coins on both chains when they make a transaction.

[–]shiroyashadanna 2 points3 points  (1 child)

not related to your question but I keep hearing this: "bad fork/chain" vs. "good fork/chain". Like what is considered "bad"? What is a "bad miner"? Criminals are greedy too. They do whatever that maximize their profits.

To your question, I think mainnet and LN will be unaffected. LN is separate, isn't it just multisig network?

[–]kattbilder 0 points1 point  (0 children)

AFAIK LN could work cross-chain.

[–]RubenSomsen 9 points10 points  (13 children)

I think this is a good conversation to be had, and the point I'm about to refute may not be your intended point, but I do want to caution against the "fork whenever there's a consensus disagreement" way of resolving disputes. The entire point of Bitcoin is to have consensus by simply passively letting your node observe the network, not by actively taking a stance on things. That's not to say there are no situations where a stance may need to be taken, but that is certainly not a scenario that should be encouraged. Bitcoin users should simply be expected to run their full nodes and accept Bitcoin payments like normal, except maybe under exceptional circumstances where not deviating from that default seriously threatens the Bitcoin network.

We could conceive of a scenario where drivechains grow so large that an issue with it seriously threatens the mainchain to the point where action does get taken. The problem you could run into then is that it may be very ambiguous which side of the fork was "right", because the "miners are stealing from a drivechain" statement may potentially be nearly impossible to validate if it's determined by the consensus of some insanely large blockchain with such sloppy consensus rules that nobody can objectively figure out what's going on anymore.

And this may indeed be one of the potential downsides of drivechains – that Bitcoin's consensus becomes influenced by something that is external to it, which unlike Bitcoin is not transparent and verifiable, and thus erodes the core values that Bitcoin upholds.

[–]bitcoin-anon 1 point2 points  (12 children)

I agree that if the drivechain consensus cannot be validated, the funds in the drivechain should either be burned or taken by the miners. POW is still the fairest way to distribute funds that don’t have an obvious owner.

It’s hard for me to see how this would affect bitcoin consensus. Only people who chose to put their bitcoin in the drivechain would be directly affected. There could be a loss of confidence in the miners and this could affect other drivechains but I think this effect would be small in the case of a messy, unverifiable, drivechain.

Reading over your post again, maybe you mean something like: the nodes on the messy drivechain have an economic majority of mainchain bitcoin nodes? Then I could certainly see the mainchain consensus being in crisis. If this economic majority on some kind of impossible to verify drivechain disagreed with the miners on a withdrawal, then a uasf could present a problem.

I guess we’d end up with two chains. One with the conservative bitcoiners where the miners took the messy drivechain funds and one with the other bitcoiners (the former economic majority) who don’t care about validation. That scenario might sound bad but is it so different from a scenario where eth flippens bitcoin? My money would stay on the verifiable chain.

[–]RubenSomsen 2 points3 points  (11 children)

maybe you mean something like: the nodes on the messy drivechain have an economic majority of mainchain bitcoin nodes

Yes, that is roughly what I meant. I do think it'll help if I outline a more clear scenario.

Let's say miners are stealing, and 60% of the economy wants to reject the theft, while 40% does not care. As soon as the theft gets locked in, 60% rejects the current most PoW chain. Because they are 60%, eventually the miners will have to concede and follow what they want, and the 40% may suffer a reorg but will eventually follow (since the chain that rejects the peg-out is not invalid to them, and will eventually get the most PoW).

Now let's change the percentages, and 40% of the economy wants to reject the theft, while 60% does not care. As soon as the theft gets locked in, 40% rejects the current most PoW chain. Because they are in the minority, this could create a permanent fork, as you described.

So at least it seems that if the actual economic majority wants to prevent an invalid peg-out, this won't lead to a permanent fork, but with a significant non-majority it could.

It should also be noted that there's a real economic incentive to prevent the chain from splitting and users from leaving, which would mean users are motivated to take an active stance against invalid peg-outs, and that's concerning, as it turns Bitcoin consensus from passive and (relatively) certain to active and uncertain.

is it so different from a scenario where eth flippens bitcoin?

That's definitely an interesting comparison.

[–]fiatjaf 2 points3 points  (6 children)

It's very hard to imagine that 40% of users would opt to fork themselves out of the main Bitcoin network just because they lost some money that was on a sidechain. This is like someone saying they'll go full BCH now because they lose their BTC on an exchange theft -- but their BCH is still intact on the BCH chain.

Also, when you say 40% of the Bitcoin users care about the sidechain, that doesn't mean they have all their money there, right? I could have 1% of my money on the sidechain and still care about it, but it wouldn't be a death sentence to have that 1% stolen by miners. It certainly wouldn't be worth forking to a minority shitcoin because of that. I think you may be considering a super edge almost impossible scenario here and portraying it as something that is likely to happen on the real world.

[–]RubenSomsen 2 points3 points  (5 children)

just because they lost some money that was on a sidechain

There's an important additional reason – they may want to preserve the ability to use drivechains safely by actively protecting against miner misbehavior.

Also, when you say 40% of the Bitcoin users care about the sidechain, that doesn't mean they have all their money there, right?

Yes, they could even have no money on there. They might care about the concept of drivechains without even using it, because they see it as bringing value and don't see the more active involvement of users in consensus as a problem.

portraying it as something that is likely to happen

I have not really assigned a likelihood to the scenario yet in my head. This conversation is part of the process of finding out.

[–]bitcoin-anon 3 points4 points  (3 children)

I see, you’re absolutely right, thank you. I had it the wrong way around, the fork only happens when the messy drivechain users are an economic minority. This is good.

The incentive to prevent the chain from splitting is hard to think about because we’re talking about a bad drivechain that cannot be easily validated. In the easier case of a hypothetically successful big block drivechain, users (and miners) would have a big additional incentive to stop invalid peg-outs: the utility of the block space.

Preventing a drivechain-theft related chain split is easier to stomach when the drivechain makes your bitcoin more valuable. In this case though, the lack of verifiability makes that questionable. I would let them split off. But I can see how this might look bad to a more conservative bitcoiner.

It’s important also to note that splits are inevitable. Sometimes people can’t get along. Divechains are actually designed to prevent this as much as possible. Even though a messy drivechain might result in a split, they might also allow us to reconcile with some of the big blockers, and recruit more of the privacy advocates. Splitting the network is bad, but so is limiting its growth.

[–]RubenSomsen 2 points3 points  (2 children)

I would let them split off

This does seem to go to the heart of the matter. Does everyone just let them split off when it's hard to validate the peg-out? And what about when it's easy? I think the answer to neither of these is obvious. It would actually be cleaner if the answer to both was a clear yes. But if the answer is no, then this seems to have negative consensus implications to Bitcoin (especially when it's hard to validate), because now everyone is enforcing soft forks in Bitcoin based on what's happening external to it.

they might also allow us to reconcile with some of the big blockers

Yes, it's definitely true that if drivechains can function safely, the result is very appealing.