Subnostr

Speaking for myself only, my primary concern about Drivechain has to do with the peg-out mechanism.

Since miners vote on withdrawals with hashrate, a 51% attacker can sweep escrowed funds. This is a new power that such an attacker did not have previously. It breaks the your-keys-your-coins contract or Bitcoin in a new way because such an attacker doesn’t have to rewrite history to carry it out.

Increasing the centralization pressure on miners is a risk worth serious consideration. Unfortunately, Drivechain proponents seem not to recognize this risk, claiming instead that Drivechain is risk-free for mainchain users.

j 2y ago

It is true that a 51% attacker can steal from the drivechain escrow. Of course, your funds will only be at risk if you put them on a drivechain, the 51% attacker would have to rewrite history to steal mainchain funds.

I don't think it follows that this increases centralization pressure on miners.

Here's how I think about it: If an entity manages to get 51% of the hashrate they can orphan blocks and win all block rewards from then on, censor transaction, increase transaction fees arbitrarily etc. Bitcoin just doesn't work if any entity controls 51% hashrate for long. Whether it's hashrate escrow funds or all future block rewards the prize for a 51% attacker would quickly become worthless since the value of Bitcoin would fall when people realized that mining was controlled by one entity.

So there's really no rational pressure for miners to centralize (as it would ruin Bitcoin's value prop). Each miner wants more hashrate but also wants Bitcoin to remain decentralized (so that the block rewards they earn continye to have value).

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Discussion

j 2y ago

What we really need to worry about is not the miners centralizing and attacking us (their incentives are aligned with Bitcoin) its the state using mining to attack Bitcoin at a loss. They would actually want Bitcoin's value to go to zero!

The best defense is lots of revenue for honest miners. Drivechains is designed to give miners more revenue.

jimbocoin 🃏 2y ago

> Drivechains is designed to give miners more revenue.

I’ve heard Sztorc make this claim. But the mechanism is unclear to me.

As I understand it, miner revenue can come from three possible sources: block subsidy, fees, and direct payments.

The block subsidy schedule is immutable, ruling that out. So does this alleged increase in miner income arise from increased on-chain fees? Or via direct payments?

j 2y ago

Merge mining fee revenue

j 2y ago

so, fees

jimbocoin 🃏 2y ago

Do you mean sidechain fees (via merged mining) or mainchain fees or both?

j 2y ago

side chains fees are aggregated and paid to mainchain miners as mainchain bitcoin in a single merge mining transaction

jimbocoin 🃏 2y ago

Makes sense. It sounds like the merge mining revenue comes out of the escrowed funds then.

The degree to which this constitutes “additional” revenue would be a function of how it compares to the mainchain revenue lost in reduced fee pressure, I would imagine.

j 2y ago

Very good point. Of course there's some things, like zero knowledge proofs, that are not possible on the mainchain and so any fees earned for those use cases are strictly a win for miners.

jimbocoin 🃏 2y ago

> the prize for a 51% attacker would quickly become worthless since the value of Bitcoin would fall when people realized that mining was controlled by one entity.

I’m more optimistic, personally, because of the possible market responses to such an attack. Censored parties can increase fees to incentivize non-censoring miners to join the network, for example.

You’re right that honest miners are disincentivized from establishing a standing majority to avoid this risk under the status quo. We have seen this empirically as miners move hash between pools when any gets too large.

I don’t know if the existential risk is sufficient to dissuade an attacker from attempting a majority escrow sweep. It is a different category of prize from previous 51% attacks, which require history rewriting.

An otherwise honest pool (or cohort of cooperating pools) can sweep escrow without rewriting history. The game theory of these interactions is not clear cut, IMO, and what we’re gambling with here is the finest money ever devised.

j 2y ago

Mostly agree here, that means only the hashrate escrowed funds would be at risk, no reason to continue the attack beyond that (that risks ruining the value prop of bitcoin).

If that happens the drivechain experiment is over and there were no negative consequences for anyone that didn't opt-in.