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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

#201

Post by setr »

bouncycastle wrote: post #170
ThrustVectoring wrote: post #142

Earlier quoted context omitted.

The attacks tend to do something like "build a chain based off Dinkycoin's previous blocks, but don't publish it until a later date". The difficulty changes can't help because the chain doesn't know about the attack until the attacker publishes a longer chain.

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.

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

#202

Post by lexs »

viraptor wrote: post #14

An update from eth classic amount linked in that thread: (not sure what they mean by selfish mining...) Regarding the recent mining events. We may have an idea of where the hashrate came from. ASIC manufacturer Linzhi confirmed testing of new 1,400/Mh ethash machines #projectLavaSnow - Most likely selfish mining (Not 51% attack) - Double spends not detected (Miner dumped bocks)

Eyal, Ittay, and Emin Gün Sirer. "Majority is not enough: Bitcoin mining is vulnerable." Communications of the ACM 61.7 (2018): 95-102.

https://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf

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

#203

Post by _Codemonkeyism »

"A vote occurred and in July 2016 it was decided to implement a hard fork in the Ethereum code [...].

Ethereum Classic came into existence when some members of the Ethereum community rejected the hard fork on the grounds of "immutability", the principle that the blockchain cannot be changed, and decided to keep using the unforked version of Ethereum."

-- Wikipedia

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

#204

Post by dmurray »

jancsika wrote: post #108
jonahx wrote: post #81

Earlier quoted context omitted.

Would you mind elaborating on this for someone unfamiliar?

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…

> 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.

Could this attack be addressed by changing the "total difficulty" function to value chains published earlier more than competing chains published later? Say a block published today is considered twice as difficult to achieve as a block starting from the same point published in 48 hours. Blocks don't need to be available in real time, but there should be enough communication between the miners to get some consensus on roughly when each block was published.

Intuitively, it seems like there is absolute agreement on the fact that a 51% attack happened (and which chain was mined by the attacker), nobody is saying "we can't be sure, this can sometimes just happen by mistake due to the distributed nature of mining". So if that can be trivially detected, why not build the detection into the mining algorithm in the first place?

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

#205

Post by profalseidol »

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…

Ethereum (the one where "The DAO" hack happened) is project that initially released in July 2015 [1]. The Roadmap was provided in the beginning and it is clearly understood that it is a work in progress. It is not yet ready for general public use.

Bitcoin is an entirely different project. Although it is also a blockchain, it's like a calculator while the former is a fully programmable computer. These two projects are very different, two different groups of developers. I encourage you read into them more to educate yourself.

[1] https://en.wikipedia.org/wiki/Ethereum

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

#206

Post by profalseidol »

martindale wrote: post #154
_n6th wrote: post #141

Earlier quoted context omitted.

You are aware that Ethereum Classic is not the same as the much, much higher-hashpower Ethereum chain, right?

The mining on that chain is largely pointless, as it's directly controlled by Vitalik. If I held assets on either, it'd be on the chain that didn't hard-fork to reverse a single user's transaction.

Mining without knowing that miners collectively have the control is largely pointless.

> If I held assets on either, it'd be on the chain that didn't hard-fork to reverse a single user's transaction.

Enjoy using Ethereum Classic then.

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

#207

Post by raverbashing »

AlexCoventry wrote: post #119
stale2002 wrote: post #112

Earlier quoted context omitted.

Well, the reality is that "attacking" a coin is much more difficult than just spending 3$ on something. You also have to actually do the double spend transactions, and hope that the person that you are stealing money from doesn't do anything about it. It is that step 2 that is actually much harder than a nieve attack might suggest.

Not really, you just have to short the coin in trading, then cover your short when your double-spend discredits the coin's security.

Yes because the crypto futures market is very well developed and is very liquid (for BTC) and exists for every tiny coin out there

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

#208

Post by thaumasiotes »

Robin_Message wrote: post #200
thaumasiotes wrote: post #197

Earlier quoted context omitted.

>> 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…

So, I just ran through the same thought process and the problem is this: How does a new entrant to the network know which is the valid chain? They didn't see the previous 20 confirmations, so the only rule they can use is picking the longest chain. Another way to do it is to have a separate voting system to attest to the "valid" chain, but then you could use an ordinary botnet to outvote the real chain. In short, con…

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 for political reasons. As a new entrant to the ETC network, how do you know which blockchain to use? Well, you use the ETC blockchain, because that's the network you're entering.

[1] I'm describing my understanding of the ETH/ETC split. If they've diverged more than I was aware of, that doesn't affect the argument; just substitute other names for ETH and ETC.

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

#209

Post by yreg »

ceejayoz wrote: post #26
semi-extrinsic wrote: post #22

Earlier quoted context omitted.

How can there be coins with $5M+ market cap where the cost of a 51% attack is $3.00 ?? In an efficient market, thieves should just immediately attack that. Or is the benefit too low?

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?

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

#210

Post by rocqua »

retsibsi wrote: post #180
xur17 wrote: post #155

Earlier quoted context omitted.

It absolutely would be easy to compare both chains and see exactly which coins were double spent, and you'd obviously be the perpetrator. Not that I advocate it, but if you wanted to carry out an attack, you'd likely target an exchange that didn't require verification, and you might exchange and withdraw under another coin (ex: trade ETC for ETH). Then spend and/or clean your ill-gotten gains.

Genuine question, forgive me if it's stupid: what happens immediately after you publish the blocks? Maybe I've misunderstood a step, but I think at this point you're in possession of a) whatever real-world goods or other currencies you bought with your bitcoins from the old chain, plus b) the same number of bitcoins on the new chain. Am I right that the value of bitcoin is now likely to crash rather quickly, as peopl…

The second spend in your double spend needs to be before the re-org is noticed. Make that spend a swap to Zcash / Monero and you can't be traced. So a full scenario would be:

* Swap coin for Zcash and start mining with 51%. * Wait until your chain is longer than the main chain, and you actually hold the Zcash. * Publish the longer chain, and immediately swap your spent coin for Zcash again. (At a different exchange just to be sure).

Now, you got twice the value of Zcash you needed, and due to Zcash shielded transactions can't be traced. You just have to hope that your shenanigans won't tank the value of Zcash.

Similar things could be done with Monero.

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