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We can confirm that there was a successful 51% attack on Ethereum Classic

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Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#231

Post by oblio »

ahje wrote: post #217
oblio wrote: post #183

Earlier quoted context omitted.

So for cryptocurrencies to be the "better solution" you just need your entire country to have a total meltdown lasting multiple years?

> you just need your entire country to have a total meltdown That happens more often than one might think. There are quite a few countries, that are currenly on the brink of collapse, so it is not unlikely that one or more of them will adopt a cryptocurrency some time in the not to far-off future.

I agree, but it's a super narrow niche for most people. Definitely one much smaller than the current hype for blockchains.

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#232

Post by dpark »

rini17 wrote: post #211
askmike wrote: post #178

Earlier quoted context omitted.

We call it a 51% attack an attack, but from the perspective of PoW it's always about the chain with the most work. Anyone is just as valid as anyone else to propose blocks. That's the point of Bitcoin: a way to always figure what the truth is, and make it as expensive as possible for people to attack/change this truth. The only problem here is that PoW only knows one cost: hashing, and due to macro shifts in mining h…

Due to probabilistic nature of most PoW protocols, you don't actually need to have the chain with the most work. Attacker can keep trying till they are are lucky, with less than 50% hashpower.

In the same way you can endlessly throw money at the craps table until you get lucky and bankrupt the casino?

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#233

Post by ceejayoz »

yreg wrote: post #209
ceejayoz wrote: post #26

Earlier quoted context omitted.

There's no demand for those coins. $PAC may have a $5M market cap, but it had $6,500 in volume in the last 24 hours. Some (most?) of that volume is likely to be people just moving stuff around rather than actual buying/selling between people. You might get rich on paper, but good luck getting anyone to help you convert your riches into spendable currency.

But even for the top currencies, it is quite cheap. Ethereum 51%/h for 106k? Wouldn't the attacker be able to get much more out of it?

That should tell you just how thin the order books actually are, despite the supposedly enormous "market caps".

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#234

Post by thaumasiotes »

Pyxl101 wrote: post #214
thaumasiotes wrote: post #208

Earlier quoted context omitted.

I don't follow this. A new entrant to the network knows which is the valid chain because the chain the network uses defines "the network". Consider the case[1] of Ethereum Classic (ETC) versus Ethereum (ETH). They are exactly the same, except for the chain each group of miners follows. The ETC blockchain is a valid ETH blockchain and the ETH blockchain is a valid ETC blockchain, but miners adhere to one or the other…

What you're missing is the process by which new blocks are added onto an existing chain. Let's say that you take the "true" Bitcoin or ETC blockchain, if you want to think of it that way, and now multiple actors are proposing to add blocks onto it, potentially multiple blocks. Which one of those additions wins? The one that's the longest and has the most work behind it - that one wins. If you propose an addition that…

> When multiple branches exist on the blockchain, some consensus process has to reconcile which of them wins. That process is that miners select the longest chain.

I've been arguing that this is a design mistake, and that the following selection algorithm would be superior:

- Instead of selecting the longest chain, select the longest chain which does not alter any blocks which I, personally, consider permanent.

Robin_Message correctly identifies that this algorithm doesn't do anything for a new entrant, because a new entrant doesn't have the exposure to history that an established miner has. But I don't see why this is an issue, as to enter a particular network, you must already copy that network's existing blockchain, and this step -- which you already have to take -- will give you the same exposure to history as the miner you copy it from.

Imagine that two blockchains, ETH and ETC, diverge for political reasons. The ETH blockchain is more beloved among the people (the laity, not the miners), and for this reason a greater number of transactions occur in ETH than ETC over time. This guarantees that the ETH blockchain will be longer than the ETC blockchain. By the selection algorithm you identify, the ETC blockchain will be wiped out, because the ETH blockchain can always be re-proposed and will always dominate it. But in reality, the ETC miners will reject the ETH blockchain, because rejecting the ETH blockchain is the whole point of ETC.

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#235

Post by acdha »

sgeisler wrote: post #162
lokedhs wrote: post #156

Earlier quoted context omitted.

Are they though? I'm honestly curious as to what those things could be. A lot of people talk about good uses of blockchains, but all examples I've seen are either not actually good uses, or they have some flaw that makes practical implementation impossible (or at least highly unlikely). What examples of good use of blockchains are you thinking of?

* Trustless time stamping to proof that you had certain information at a certain point in time without revealing it https://opentimestamps.org/ * (depending on your stance on personal liberty) censorship resistant, pseudonymous e-cash/e-gold (Bitcoin)

> censorship resistant, pseudonymous e-cash/e-gold (Bitcoin)

Bitcoin not only doesn’t deliver on those claims, it’s actively dangerous because it leaves an immutable public record of your activities, as numerous court cases have shown. There’s a reason why the mob doesn’t publish their ledgers.

“Censorship resistant” is also a complex claim since the network is trivially blocked as a whole, and the inability to comply with legal demands means that anyone legitimate faces risks which will encourage them to stop participating, reducing the defense for allowing it at all and removing the traffic everyone else is hoping to hide behind.

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#236

Post by ric2b »

nostrademons wrote: post #67
hacker_9 wrote: post #3

Amazing, this blockchain technology really just keeps on giving. I have to say, it's quite entertaining to watch. It's pretty much a car crash happening in slow motion at this point. At least it provides something else to nerd joke about by the watercooler that isn't brexit for once.

That's what it was like in 2016. I remember seeing the headline for the DAO hack on HN back then and thinking "Wow, good thing I didn't invest in this Ethereum thing". Someone had told me about it in 2015, I took a quick glance and passed thinking "Looks like a scam." Then 2017 happened and the joke was on me. Then 2018 happened and the joke was on them again. New technologies are always shitshows when they get start…

> Someone had told me about it in 2015, I took a quick glance and passed thinking "Looks like a scam." Then 2017 happened and the joke was on me. Then 2018 happened and the joke was on them again.

Pretty sure the joke is still on you when comparing to someone that told you about it in 2015.

The highest price for ETH in 2015 was $2.19, lowest in 2018 was $85. So even with the worst possible entry/exit in those years we're still talking about a 3881% ROI in 3 years. Again, that's the WORST possible ROI for entering in 2015 and leaving in 2018.

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#237

Post by ryani »

thaumasiotes wrote: post #197
askmike wrote: post #192

Earlier quoted context omitted.

> They do; for a transaction to be revocable means you haven't accepted that it went through. If every block is revocable indefinitely, then you can't say that 20 confirmations confirm a block, because they don't. From the blockchain perspective a block with a confirmation is confirmed. But everyone else can make new rules on top regarding payments: Do you consider most crypto exchanges to not support "Bitcoin" since…

>> With a consensus of decentralized, less-than-perfectly-synchronized miners, you'd want a fuzzier boundary -- which is what "wait for 20 following transactions" provides. > This is done to raise the cost of reversing the transaction (the more confirmations deep, the more expensive your attack needs to be). No, it isn't done at all. You state as much: > From the blockchain perspective a block with a confirmation is…

Let's say there was a catastrophic event that split the internet and disconnected Australia and the surrounding islands from the internet for 36 hours.

Let's also say for the sake of argument that 10% of the BTC mining capacity is in that region.

The network self-adjusts so that every hour 6 blocks get confirmations, but over this short time period you wouldn't expect this to happen. This means that every hour the Australia split would confirm 0.6 blocks and the non-Australia split would confirm 5.4 blocks.

After 36 hours Australia would have confirmed ~21 blocks, and according to your proposal, the first of these is now 'accepted' and can't be rolled back.

In the same time the remainder of the network would have confirmed ~194 blocks, many of which are now accepted.

What would actually happen according to the consensus protocol is that RestOfWorldBTC is the longer chain and therefore "is" BTC, and AustraliaBTC would get thrown away. Any BTC transactions made in Australia during that time would get rolled back.

But if blocks become permanently accepted then these 2 chains are fundamentally incompatible; they are no longer the same coin. Your proposal says that the network should fork into 2 coins here -- AustraliaBTC and RestOfWorldBTC. This would be a pretty disruptive event. People who traded BTC for services in Australia would claim that they paid their obligation (after all, it's in an 'accepted' block) and therefore don't owe their counterparty any RestOfWorldBTC. But AustraliaBTC would likely become worthless very quickly, given that most of the transactions in those 36 hours were confirmed on the RestOfWorldBTC chain. Australian counterparties would get stiffed pretty hard.

OTOH, if you roll back those transactions and accept the mainline, those counterparties can more easily argue that you still need to pay them. Note that the network can't enforce you paying these obligations, but the legal system still exists! And assuming the actors were acting in good faith and didn't attempt to double-spend their coins, their transaction would get re-propogated automatically and get included in a future RestOfWorld BTC block once the network split ended.

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#238

Post by SilasX »

thaumasiotes wrote: post #179
jancsika wrote: post #108

Earlier quoted context omitted.

Imagine all the Bitcoin miners out there right now using their ASICs to do extremely efficient hashing in the hopes of generating a block reward. Let's didactically suppose there are 100 such miners total. Now imagine Dinkycoin comes along and releases their cryptocurrency that uses the same hashing mechanism for the block reward. Initially they have the block difficulty level pretty low as there aren't that many peo…

> suppose Dinkycoin says you need 20 confirmations before accepting that a transaction "went through." > Once the Bitcoin miner has a competing branch with greater total difficulty than the rest of the network, the network must accept that branch as the winner. These statements directly contradict each other. The very, very obvious solution is to say that, if 20 confirmations validate that a transaction happened, the…

But once you start forcing the agreement that "this specific history up to block X is the official one", you're re-introducing centralization, which Bitcoin was introduced precisely to avoid.

Sure, it's less centralization than just trusting one party to determine the latest block [1], but it's a matter of degree.

[1] The further you go back in time/blocks, the less disagreement and resistance there will be to locking in a history.

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#239

Post by jki275 »

mikeyouse wrote: post #104
jonahx wrote: post #81

Earlier quoted context omitted.

Would you mind elaborating on this for someone unfamiliar?

Most proof of work coins use unique hashing algorithms and the miners are custom-designed ASICs that are extremely efficient at that one specific algorithm. If per chance, your coin uses the same algorithm as Bitcoin [ SHA-256(SHA-256(Block Header)) ], a small portion of the much larger Bitcoin mining community could turn their miners toward the smaller coin and quickly overwhelm their network to perform a 51% attack…

Doing the attack tends to drive said shitcoin's value to zero, so the incentive to do it is often not there.

Re: We can confirm that there was a successful 51% attack on Ethereum Classic

#240

Post by jki275 »

setr wrote: post #201
bouncycastle wrote: post #170

Earlier quoted context omitted.

Yes, of course! And once the damage has been done, it's even harder to reverse. Perhaps if Dinkycoin's devs are fast enough, they could release a fork to undo it?

As long as the attacker maintains 51%, he can eventually just repeat the attack, regardless of the number of forks.

You change the POW function in the fork to eliminate the attack.
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