Comment by turkeytotal | Hacker News Reader

Comment by turkeytotal | Hacker News Reader

Parent Full thread

That is a contentious hard fork with a rule change, completely different from a normal fork caused by an orphan race. With proof of stake there is no marginal cost to playing multiple forks, ultimately opening up the network to a flood of competitive same-rule forks that have to be resolved using "weak subjectivity."

Adding layers of complexity like Ethereum's Casper to solve the incentive incompatibilities caused by the nothing at stake and long range attacks do not address the fundamental issues, as consensus then require users to agree on a list of bonded validators (for which there is no switching cost). "Phone a friend" consensus is objectively weaker as a security model compared to POW which just requires users to validate the rules and calculate the chain with the most work.

POW is secure because it requires energy from outside the system to be provably burned. It's thermodynamically sound in that respect. /u/nullc recently described POS as a logical tautalogy which I think captures the issue well. If chains were a car, Bitcoin would be fueled by gas and a POS coin would be fueled by the leather on the seats. You're not going to get very far.

> It's thermodynamically sound

Due to the algorithms being inefficient

If that is resolved then the entire history will be suspect

And any thermodynamically similar future will have to compete on constants and exponents

Or you could regulate the hardware, 'this blockchain is only compatible with, and so calculated on, a gateway lt1700 with exactly 640k of ram' ;P

>> It's thermodynamically sound

> Due to the algorithms being inefficient

This is by design, when the hardware gets better Bitcoin network starts requiring even more work, so being "efficient" is actually what is not desired here. See: https://en.bitcoin.it/wiki/Difficulty

You seem to have a deeply intuitive knowledge of blockchain tech, and you've posted with a throwaway. I'm assuming you are a well known member of the community.

At risk of being petty, no, they don't and aren't. See sibling thread: they're not disputing the core point I raised (that PoW schemes are not immune to being weakened by forks), but changed the topic to different one and seem to have copy-pasted general arguments in favor PoW. (It's copypasta because they have a cryptic reference to a poster on a different forum, /u/nullc that doesn't help us find the argument here without searching their history on reddit [I guess.])

It doesn’t sound like you’re disagreeing with my claim that forks under PoW (at least of a specific kind) can make the branches vulnerable to attack as soon as the hash power sloshes away; your comment is only speaking to PoS and a different kind of Bitcoin fork that doesn’t match the BCH one.

No, I am disagreeing with you. You are claiming that the hashpower oscillations between BTC and BCH contradict the GP's comment, when in fact you have you missed exactly what I and the GP have said:

>the miners must select one chain to mine

I am pointing out that the "sloshing" is in fact perfect evidence that they are only mining one chain at a time, or splitting their hashpower to varying proportions. This is completely normal and healthy miner behavior, they are simply greedy actors looking for the most profit. They cannot however mine both chains with their full hashpower for free (as you can with PoS), and this is an essential understanding when analyzing the security model of a consensus algorithm.

Also, the oscillations are most commonly exploitable only when the difficulty adjustments happen very quickly (see: BCH's EDA), so if 70% of the hashpower left, even if 16% of the remaining hashpower was malicious, the efficacy of a 51% will be handicapped by the disproportionately high difficulty.

Sorry if I’m being dense here, but I don’t actually see how you’re disputing that the threshold for attacking a single fork has (in the example) fallen from 51% of all bitcoin-capable miners, to 16%.

I don’t care whether sloshing is “normal healthy behavior”. I care whether a fork has become easy to attack. You seem to focus on every topic but that one.

I guess you are missing the entire point of this conversation. It is about the marginal cost of participating on multiple chains with PoW. You can point out oscillations as much as you like, it doesn't change the marginal cost. You are pointing out something that is entirely orthogonal.

Your point was different from my point. I entered the thread to dispute that PoW schemes aren't weakened by forks. Here's the exchange where I came in[1]:

Original comment: "Also, with Proof of [Work] you get protection against an explosion of too many hard forks..."

My reply: "That's not what happened with the Bitcoin Cash fork though ... any given time, one of the networks is easy[er than 51%] to attack."

If you're not disputing that point, then you're not refuting my objection to that original comment.

[1] https://news.ycombinator.com/item?id=15606486

Reply on news.ycombinator.com