Regardless of a pleasant few months this summer season after Burak, notorious slayer of the Lightning Community, dropped his proposal for the brand new second layer protocol Ark the place folks had plenty of dialogue round completely different covenant proposals, drivechains are as soon as once more changing into a dominant matter of dialogue. There are numerous issues with drivechains, from the rationale for supporting them, to claims about how they do not have an effect on incentives being inaccurate, and even causes for why they could truly damage miner earnings as a substitute of accelerating it. On this piece I’ll focus solely on the problems concerning incentives for brevity’s sake.
In case you are not acquainted with the particular technical workings of BIPs 300 and 301, you may learn a succinct abstract of that right here.
Separation of Considerations: Mainchain Miners and Sidechain “Miners”
One of many core claims from drivechain proponents is that the activation of this BIP introduces no new necessities or prices for miners who take part in securing these sidechains. Whereas that is strictly technically true, it doesn’t require or mandate something new from miners, the incentives of the design naturally create a funnel motivating miners to tackle full duty for operation of those sidechains themselves to maximise revenue. Over time as a result of aggressive nature of mining, this may ultimately make miners operating sidechain nodes and dealing with block building themselves to take care of their financial competitiveness.
The design of blind merge mining (BMM) in BIP 301 specifies a mechanism for customers who don’t interact in Bitcoin mining to overtly bid within the mempool for miners to pick out their sidechain block for affirmation. For miners to simply accept a particular bid from some sidechain “miner” they need to embrace an identical dedication to choosing their block of their coinbase transaction. The consensus guidelines of the proposal make any bid transactions from sidechain miners invalid until the corresponding message is included within the coinbase. This each ensures that miners can’t declare funds from a sidechain miner until they really verify their sidechain block. It additionally prevents them from claiming funds from a number of sidechain miners whereas solely commiting to certainly one of their sidechain blocks.
The proposal is designed this manner with the aim of permitting miners to gather income from sidechains with out having to really validate them or contain themselves in developing blocks for the sidechains. In accordance with proponents, sidechain miners will merely bid the charges paid to mainchain miners as much as be nearly everything of the sidechain’s earnings, and miners will seize ~99% of the worth with out having to do something. This assertion utterly glosses over the truth and nuances of the incentives concerned on this association.
It’s recurrently claimed that “anybody can take part in developing sidechain blocks.” This isn’t true. Whereas it’s an open course of to take part in, it is not free. It requires capital within the type of bitcoin to really be a sidechain miner, and this capital requirement grows in proportion to the expansion in payment income generated by a particular sidechain. So if a sidechain generates solely 0.0001 BTC per block, it is going to be a really open course of that nearly anybody can take part in. However as an example that sidechain generates 1 BTC in charges every block, that may be a very completely different sport. Additionally, the withdrawal interval for a drivechain is three months; that is roughly 90 days earlier than you may truly withdraw something you have got earned, so at 1 BTC per block with 144 blocks in a day as much as 12,960 BTC are required to pay miners for confirming sidechain blocks. Consider in principle it is a aggressive factor, in order that price can be break up between all of the profitable sidechain miners, however that’s nonetheless an enormous quantity of capital (only for one sidechain). Even a extra modest 0.1 BTC remains to be 1,296 BTC in that interval.
This brings me to the crux of the issue. Do you actually assume that almost all of the charges collected on a sidechain are going to be paid to miners? Individuals will collectively half with and put in danger over 1200 BTC in a 3 month interval simply to have a shot at incomes a piece of 12 BTC? The complete rationale for miners by no means having to do something is that ~99% of accessible income can be given to miners attributable to aggressive pressures, and it’ll not be definitely worth the 1% reward to mine the sidechain’s themselves. That 12 BTC represents the 1% left over. Over 1200 BTC is in danger for the potential reward of 12 BTC. If that assumption is fallacious, and sidechain miners that aren’t additionally mainchain miners won’t spend that quantity of capital for that low of a return, then there’s a a lot greater % that mainchain miners should not capturing on the desk. The one solution to seize it in that scenario can be to turn out to be a sidechain miner themselves too. Miner’s complete incentive is to maximise revenue, leaving important revenue on the desk will inspire them to seize it. And this is the ultimate kicker: miners need not have and spend that BTC capital up entrance with the intention to mine the sidechain, they only have to stay a dedication to a sidechain block of their coinbase. For the miners themselves that is free.
The belief of how a lot of the charges can be paid to mainchain miners being fallacious primarily creates an incentive spiral that results in the very same kind of mining centralization stress conventional merge mining or one thing like a blocksize enhance would create. In different phrases, it means the declare about BMM fixing mining centralization is fake.
Second Layer Price Sniping
One of many sport theoretical considerations with Bitcoin long run is a matter referred to as payment sniping. Publish block subsidy when most of miners’ income comes from charges, when irregular payment spikes happen, miners truly do have an incentive to carry out brief reorg assaults and battle over blocks that accumulate these abnormally excessive charges. Proper now if an enormous payment spike happens miners can at all times depend on the block subsidy within the subsequent block even when they missed out on that payment spike. As that subsidy disappears and miners rely upon the variance of the payment market alone to pay the payments, exaggerated sufficient spikes in charges change the equation and make it price reorging (or redoing work) for a time to battle over that exaggerated earnings. This may make sense till the price of redoing work on the identical block time and again with no reward collected approaches the purpose of being an financial loss, after which miners would rationally stop the battle.
The way in which that drivechains BMM specification works adjustments the dynamic of this. In conventional merge mining you would need to reorg the mainchain with the intention to reorg a sidechain. In drivechains you do not. The identical manner that mainchain blocks have a pointer again to the earlier block, drivechains do as effectively. The factor is, you do not have to take away a dedication to a sidechain block with the intention to level to a distinct one. Have a look at this instance under, the numbers in parentheses are the blocks the present one is pointing again to:
A sidechain block when utilizing drivechains is simply one thing dedicated to within the mainchain, and whereas the mainchain goes marching ahead with out going again, the sidechain can travel between a number of forks. The sidechain software program remains to be following a longest chain rule (which miners are trusted to respect), however in contrast to the mainchain reorgs these blocks do not simply disappear. The dedication to them nonetheless exists within the mainchain, and nonetheless must be scanned.
So what does this need to do with payment sniping? Every little thing. For miners to payment snipe on a sidechain it would not require redoing work, it would not require giving up the mainchain charges (and even charges from different sidechains). So when that sidechain miner collects twice the charges as regular and solely pays the mainchain miners what they usually do, a mainchain miner can come alongside and reorg that block on the sidechain and accumulate the sidechain charges whereas the miner who acquired cash on chain for the unique model of that sidechain block nonetheless retains that payment. So the unique sidechain miner earns nothing, and loses what they paid in mainchain charges. So one miner can feesnipe with out the primary miner dropping what they earned. If a miner will get fortunate, the identical miner may even double accumulate the unique payment on the mainchain and the sidechain charges by reorging it in the event that they mine two blocks in a row. Solely the sidechain miner who would not mine on the mainchain loses cash on this scenario, and since they don’t even have hashrate there’s nothing they’ll do about it.
Now to ensure that the mainchain miner to efficiently pull this off, the sidechain miners need to construct on their block as a substitute of the unique. If a pool is large enough, they’ve respectable odds of simply discovering the subsequent block themselves, the place in fact they are going to construct on their very own block. They may even overtly bid like a sidechain-only miner to extend their odds. This may require paying an precise mainchain payment, however the preliminary reorg was free. Different miners may even simply construct on the reorg block as a substitute of the unique as a result of it’s newer, these particulars come right down to how the precise software program implementation swimming pools deploy is constructed.
General although there’s a giant asymmetry in threat between sidechain-only miners and mainchain miners in relation to sidechain reorgs. Mainchain miners who’ve a sidechain block reorged from them endure the chance price of dropping further potential income, sidechain-only miners truly lose cash they already had. And all of this happens with no reorg disruption to the mainchain itself. It is a large drawback, and disincentive, for sidechain-only miners to take part on this course of.
Even eradicating sidechain-only miners from the image, this dynamic change nonetheless exists in a scenario with solely mainchain miners. If we take a look at mainchain miners doing this to one another although, the truth is it’ll doubtless fall into equilibrium the place everybody is not reaching optimum earnings, however better than they’d with out sidechains. Some may query whether or not that may prevail on condition that 26% of miners can cease all pegout transactions from sidechains, and that the tail finish of swimming pools may achieve this in protest of disproportionate advantages for bigger swimming pools. All that may accomplish is to create an natural incentive for almost all of miners who stand to realize from the withdrawal going by means of to orphan the mainchain blocks of the miners stalling it. So whereas this nonetheless disproportionately advantages bigger swimming pools who will statistically discover a number of blocks in a row extra usually, smaller swimming pools have an incentive to simply accept it. This dynamic is yet one more centralizing stress for miners by itself, and in addition another excuse the incentives push the association in the direction of miners validating and mining these sidechains themselves.
MEV
Miner Extractable Worth is changing into an enormous downside, notably within the ETH ecosystem. MEV is any kind of technique to revenue the place the miners/stakers/and so on. have an uneven benefit over everybody else in gathering that revenue. Sometimes that is accomplished by means of controlling the order of transactions in a block, akin to trades interacting with a DEX contract, however in summary that isn’t strictly obligatory. The revenue margin that sidechain-only miners hold for themselves mentioned above is itself a really primary type of MEV, it’s worth sitting on the desk that miners have a bonus in having the ability to declare. This type of MEV isn’t very difficult, costly to research, and is well extractable by mainchain miners merely operating primary sidechain software program.
Let us take a look at a transaction ordering type of MEV, like a DEX on ETH. Decentralized Change protocols permit non-custodial buying and selling of belongings between buying and selling events utilizing a sensible contract as a mediator. It atomically fulfills either side of the commerce, or none. The factor is although, if you may make a revenue in making such a commerce, the one solution to accumulate it’s if miners embrace that transaction in a block. And the easy reality of broadcasting that transaction offers miners the within scoop on out there revenue earlier than it is truly confirmed in a block. This offers them the chance to entrance run you and accumulate these earnings for themselves. A sidechain-only miner participating in such actions would doubtless have the ability to bid a lot greater than different sidechain miners, getting a lot nearer to 100% of the payment rewards instantly out there in that block. Nonetheless, in doing so that they sign to mainchain miners that a chance for even better revenue exists. Provided that F2Pool is at the moment taking part in MEV video games entrance operating different Stacks individuals, Luxor bought and is constructing out Ordinalshub, miners trying to generate new streams of income is a reality of actuality and never a hypothetical. That is yet one more incentive for miners to turn out to be sidechain miners themselves.
However the MEV threat would not cease there with simply extra miner centralization threat. There are conditions the place miners can’t simply simply seize the MEV worth themselves. Say an organization or group ran a entrance finish for an enormous DEX to make it simpler to make use of (nearly each DEX on ETH has such gamers), and sourced the person orders earlier than they even hit the mempool and privately constructed a block to bid for to mainchain miners. Mainchain miners would not have the ability to examine the contents of this block till after it was confirmed and propagated between sidechain nodes, so they are going to be incapable of frontrunning within the mempool to extract this worth, they must truly reorg and feesnipe the sidechain. This clearly would damage the sidechain miner working the DEX entrance finish and the mainchain miner may be double paid, however the mainchain miner can by no means truly extract this worth himself entrance operating the mempool as a result of the precious transactions by no means enter it. And by reorging and placing the sidechain miner/DEX entrance finish operator out of enterprise, they’re destroying that supply of worth. That is a extra concerned effort, and extra divergent from their fundamental enterprise of simply operating nodes, or selectively changing issues they see of their mempool.
There are additionally conditions the place mainchain miners extracting MEV is basically unattainable. Think about a sidechain spun up particularly to facilitate funds for items on Amazon, or combine with some Amazon cloud service. The oblique new income this sidechain’s existence may generate is actually solely capturable by Amazon. For miners to extract that worth, they’d actually need to construct an organization that may out of date and substitute Amazon. That is simply not occurring.
So ultimately not solely do MEV dangers on drivechains exacerbate incentives for mainchain miners to instantly take part in them, it additionally has the potential of introducing exterior affect into mining incentives. What if Amazon solely shared its MEV worth with the few largest swimming pools? It might incentivize miners to modify to them to earn a minimize. It offers them a level of direct affect over miners income streams.
However Merge Mining Already Exists
That is the frequent response to those considerations: merge mining already exists. Sure, it does, however for freely valued shitcoins. Namecoin is the frequent instance introduced up, however Namecoin represents primarily nothing in share phrases of miners earnings. Quite a few SHA256 cash have been merge mined with Bitcoin, nearly none of them are anymore as a result of their worth crashed to the purpose of it not being definitely worth the effort. That’s the empirical historic development right here. These techniques observably don’t pose wherever close to the identical incentive threat as a coin pegged to Bitcoin, that can’t merely independently crash in worth to the purpose that it isn’t price involving your self with.
Some folks may convey up federations, however the actuality is nobody appears to have curiosity in utilizing federated sidechain pegs. They generate no demand, the place there appears to be loads of clambering for a drivechain hashrate escrow peg. That might essentially alter the equation right here and create demand giant sufficient to trigger damaging incentive distortions the place they in any other case would not exist. On the opposite aspect, mining swimming pools organising a federation would supply no actual dynamic membership to who controls the cash (as the present keyholders must explicitly add new members and switch cash), and features no actual worth from being merge mined. It is usually one thing mining swimming pools that begin it may run independently of precise miners, i.e. if 100% of hashrate left mining swimming pools that began a federation, the swimming pools with no hashrate may nonetheless function it. They may signal blocks, and any prior merge mined scheme is basically meaningless as a result of the swimming pools management the cash on chain. It is primarily only a federation like Liquid that has some phantasm of an overlap with mining at that time.
So, the large claims concerning drivechains are that mainchain miners do not need to care about them, and that they don’t alter mining incentives in any manner. I’ve laid out the most important (however not at all all) of the arguments exhibiting they do in truth alter them in very substantial methods. These prices must be one thing severely thought-about when considering this proposal, as regardless of the declare by many drivechain advocates, they’re very actual.
