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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

#261

Post by CydeWeys »

Semaphor wrote: post #174
CydeWeys wrote: post #47

Earlier quoted context omitted.

It's really obvious once the new chain is broadcasted. "Honest" miners switch over to mine on the deepest chain as soon as they become aware of it. It's very rare to even see a 2-block conflict. When you see a large N-block conflict then it's obvious there's a 51% attack going on.

But isn't the point of the whole thing that you do not broadcast it until after you are done? So yes, it's obvious in hindsight, but the damage will be done.

The question was how do you detect it. You obviously can't detect it until it's broadcasted because until then it's all happening in secret.

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

#262

Post by CydeWeys »

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?

The thing is, the amount of GPU processing power required to attack Ethereum is not readily available, and certainly not at a cost of only $106k. That $106k figure comes from extrapolating out marginal rental cost of a single GPU, never mind that there aren't enough GPUs rental to overwhelm the whole network.

To give you an idea, the overall Ethereum network is currently 190 PH/s, so you'd need significantly more than that to have a high chance of launching a short term attack with reasonable success rate (if you only control 51% then your odds actually aren't great). Let's say you need 300 PH/s.

Well, the average modern AMD graphics card that is suitable for mining Ethereum only does around 30 MH/s. That means that you need 10 million such graphics cards. They simply aren't available for rental anywhere at such scale.

That's why you're not seeing such an attack happening. The raw monetary figures are misleading.

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

#263

Post by CydeWeys »

thaumasiotes wrote: post #258
Robin_Message wrote: post #257

Earlier quoted context omitted.

> guarantees that the ETH blockchain will be longer than the ETC blockchain. Chain length is number of blocks, which is controlled by miners, not "laity". I think your system might prevent double spends; unfortunately it would do so by rendering the network unusable for any new users, who wouldn't have a way to know which is the good network to join. I suppose a central authority could be used to identify the good ch…

> Chain length is number of blocks, which is controlled by miners, not "laity". A block is a set of transactions, transfers of currency from one address to another address. Miners don't just add blocks because they're bored. They add blocks when someone submits a transaction. So the number of transactions that occur is closely related to the number of blocks in the chain.

This is very wrong.

Of course miners are always adding blocks, even when the blocks are empty; they do so because there is a block reward. Even empty blocks, when mined by honest miners, are serving a purpose, because they are increasing the cost of a 51% attack. Look through the histories of many different blockchains and you'll see empty (or nearly empty) blocks that exist for a variety of reasons.

Also, transaction sizes differ drastically depending on what a transaction does, and blocks max out at a given size, not a given number of transactions. So when blocks are full (which they aren't most of the time except for the very highest used cryptocurrencies) the number of transactions per block still varies quite a bit.

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

#264

Post by CydeWeys »

Robin_Message wrote: post #257
thaumasiotes wrote: post #234

Earlier quoted context omitted.

> 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…

> guarantees that the ETH blockchain will be longer than the ETC blockchain. Chain length is number of blocks, which is controlled by miners, not "laity". I think your system might prevent double spends; unfortunately it would do so by rendering the network unusable for any new users, who wouldn't have a way to know which is the good network to join. I suppose a central authority could be used to identify the good ch…

It's worth pointing out that it's not chain length which ultimately wins out, but chain weight, which is the sum of the difficulties of each block on a given chain.

This is an important distinction, because by fudging timestamps you can generate a valid chain of arbitrarily long length where each block has very low difficulty, but said chain would still not be preferred over a chain with fewer blocks of much higher difficulties (i.e. the real chain).

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

#265

Post by CydeWeys »

krrrh wrote: post #166
skwirl wrote: post #99

Earlier quoted context omitted.

>But if you tried to sell some significant fraction of the outstanding coins then the sale price would plummet, and you'd never actually reach $5M total. You can't focus on sellers and ignore buyers when discussing the valuation of something. If many people want to sell and few people want to buy the price will of course go down. But if many people want to buy and few people want to sell then the price will go up. Th…

Another salient point is that when an entity buys all the shares of a company they pay a premium over the current share price indicating that the company is perceived by the market to be more valuable with a single shareholder than with widely dispersed shares. A cryptocurrency with a single sharehodler is a non sequitor and essentially worthless.

You've put it into words better than I have. To acquire all shares of a company requires a premium, but to acquire all shares of a crypto makes it worthless. Companies and cryptos are not remotely the same thing and frankly "market cap" is a misnomer when applied to cryptos; it misleads more than it enlightens.

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

#266

Post by CydeWeys »

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.

And the chance of successfully doing so is incredibly low, and meanwhile you're out all the computational resources you spent on your private chain that ends up being thrown out.

You'd be better off simply placing big bets at a casino

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

#267

Post by matte_black »

rando444 wrote: post #216
matte_black wrote: post #159

Earlier quoted context omitted.

Which government will prosecute?

The person they are swindling can go through their own authorities, and if the authorities in the criminal's country are alerted to his activities, they can go after them as well. Theft and fraud don't take on different meanings just because the currency is digital.

So basically it sounds like you'll never get caught.

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

#268

Post by landryraccoon »

butisaidsudo wrote: post #153
xur17 wrote: post #139

Earlier quoted context omitted.

> You can increase your chances by increasing your mining percentage. Make it a 75% attack and you have an 18% chance of success. To have a 50/50 chance of success you really need to mount about a 90% attack which is pretty ambitious. I'm not sure this is accurate. You don't need to mine 6 blocks in a row on the existing chain. Clients are programmed to recognize the longest chain, so you just need to silently mine n…

I'm trying to understand what "cashing out" would look like in an attack like this. One option would be to send coins to an exchange as you mentioned, and I presume cash them out before publishing your longer chain. However, after the attack wouldn't it be easy to compare both chains and see which coins were double spent? Wouldn't you obviously be the perpetrator, having both double spent, as well as having cashed ou…

You cash out by having a vested interest in damaging the exchange or currency in general. Say for example a hedge fund that shorts all crypto exchanges, or a competing cryptocurrency that wants to undermine confidence in their competition.

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

#269

Post by garmaine »

koheripbal wrote: post #254
garmaine wrote: post #186

Earlier quoted context omitted.

A system that has effectively bifurcated with conflicting chain tips caused by rewriting history with new nodes unable to tell which is original, or a fully centralized stake-mining where a subset of stake voters game the system to unfairly select themselves out of proportion of their stake weight.

Is that reeealy so different from a PoW fork?

A proof-of-work fork is an unstable situation, resolved when more work is applied to one side vs the other, which inevitably happens without active intervention. A proof-of-stake fork is permanent--someone new to the network has no built-in mechanism for deciding which side to prefer: they both seem equally valid.

A properly constructed proof-of-work mechanism has no built-in mechanism for a malicious minority hash power to take control of the protocol, shutting out the higher hash rate majority from mining blocks.

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

#270

Post by garmaine »

jki275 wrote: post #241
garmaine wrote: post #113

Earlier quoted context omitted.

Proof of Stake is a perpetual motion machine. You can't safely tie consensus to something (stake) which is determined by consensus. That's circular reasoning and ungrounded.

And yet we have multiple Proof of stake coins that seem to work just fine.

Until they don't. There have been proof-of-stake failures before, and there will be more. Every proof-of-stake system is either (a) known to be broken, or (b) too complicated to analyze to show how it is broken. As the exploitable order depth in category (b) increases, it becomes worthwhile to invest the hours, days, weeks, months it takes to develop attacks against these Rube Goldberg contraptions and they get moved to category (a).
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