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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

#31

Post by naveen99 »

pietjepuk88 wrote: post #25
aetherspawn wrote: post #2

What does this mean? (Not all of us know a whole lot about how crypto works or why this is good or bad and what it means for our investments)

The most typical way to profit from this, is to have quite a bit of ETC, and then sell it on an exchange or buy something expensive. This transaction would then end up on the block chain, and eventually be considered secure / part of history. Privately, you are building a chain where said transaction did _not_ occur. Because your hash rate is high enough, you are generating blocks at at least the pace of the public c…

so to be safe, an exchange should require more confirmations depending on size of deposit. Basically the number of confirmations you could finance an attack for with the deposit.

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

#32

Post by Klathmon »

kryogen1c wrote: post #21
Klathmon wrote: post #6

Earlier quoted context omitted.

That's like saying "this whole programming thing just keeps on giving" every time a bug is discovered in any program. Those involved have been warning of the insecurity of smaller chains for a long time now, and they aren't representative of the entire ecosystem.

> That's like saying "this whole programming thing just keeps on giving" every time a bug is discovered in any program. No it's not. Programming is a tool to create programs with. Block chain is a technological buzzword being used (and implemented) wildly inappropriately. 51% attacks are a fundamental vulnerability in decentralization. It would be like inventing programming when everyone pretends bugs don't exist at…

You won't find any disagreement from me that there is a LOT of garbage out there using blockchains and cryptocurrency tech inappropriately.

The extreme vast majority is trash, manipulative, and awful in most every way. Not to mention the charlatans and fanboys that hype it as able to do everything and anything perfectly.

But the few that use it well are doing fairly well, and innovation is happening. You shouldn't loop the entire ecosystem as one big unit making terrible choices together.

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

#33

Post by makomk »

orblivion wrote: post #11
bonyt wrote: post #8

Earlier quoted context omitted.

In this kind of blockchain network, the longest chain of blocks is considered to be the valid one. However, someone that has 51% of the hashing power (i.e. more hashing power than everyone else combined) can create a chain that grows faster than the chain used by everyone else. This means that they could tamper with their chain, potentially rewriting history on it, and because it is the longest chain, it will be acce…

Being only somewhat familiar, I wonder this: Why don't clients have a simple rule against accepting changes to history that are more than one or two blocks old?

In short, because they don't know that the chain they saw first is the chain that other nodes saw first (especially if they weren't online at the time). At least in theory, an attacker can exploit this to permanently fork the chain.

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

#34

Post by acomjean »

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.

To be fair, as someone who is cynical and lived through the turn of the century dot-com crash we needed a few high profile failures after the pets.com sock puppet, myspace and cue-cats almost 20 years ago.... Thank goodness for Amazon...

But honestly I missed the crypto currency expansion completely. Bitcoin when I noticed it at $50, bah.... It hasn't lived up to its promise of an alternative form of payment, but it certainly increased in value rapidly. But I wouldn't count it out completely, there may be a use case that in hindsight is obvious, that we aren't seeing yet. I doubt it but it is possible (my track record is good but mixed. I was the proud owner of buy.com stock.. that didn't work out so well.. )

Plus the algorithms are kind of interesting, and the fact it works at all is kind of miraculous.

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

#35

Post by tuesdayrain »

kryogen1c wrote: post #21
Klathmon wrote: post #6

Earlier quoted context omitted.

That's like saying "this whole programming thing just keeps on giving" every time a bug is discovered in any program. Those involved have been warning of the insecurity of smaller chains for a long time now, and they aren't representative of the entire ecosystem.

> That's like saying "this whole programming thing just keeps on giving" every time a bug is discovered in any program. No it's not. Programming is a tool to create programs with. Block chain is a technological buzzword being used (and implemented) wildly inappropriately. 51% attacks are a fundamental vulnerability in decentralization. It would be like inventing programming when everyone pretends bugs don't exist at…

Blockchains are just another datastructure. A poor implementation of one doesn't necessarily mean the whole idea is fundamentally useleas.

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

#36

Post by [deleted] »

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)

[deleted]

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

#37

Post by gus_massa »

eloisant wrote: post #9
aetherspawn wrote: post #2

What does this mean? (Not all of us know a whole lot about how crypto works or why this is good or bad and what it means for our investments)

Because crypto-currencies are validating transactions by having them validated by the network as a whole, a group who controls more than 50% of the computing power can do whatever they want: reject valid transaction, create (and validate) fake transactions...

You can't create fake transactions[1]. You can reject some valid transactions or reject all transactions freezing the network for some time, and also try to double spend your money.

[1] The idea is that the miner just pick the last block and select a bunch of the current transactions and a random number and makes a hash of all of them. If the hash has enough zeros at the beginning then it is a new block and it is distributed to all the network. The other nodes of the network validate all the transactions and also that this bunch of transactions with this random number produce a hash that has enough zeros at the beginning. Any invalid transaction of a wrong random number make all the other nodes of the network ignore the fake block.

Once the last block and the bunch of transactions are picked, the difficult part is selecting a random number that with them produces a has that has enough zeros at the beginning. So the mines must try, try, and retry with different random numbers until they are lucky (or someone else is lucky). They must try millions of millions of millions (gillons?) of times, because it's difficult to pick the correct one. This uses a lot of electricity to power the computer. The other people just validate with the lucky number, so it's much cheaper.

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

#38

Post by nickik »

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.

That's why Proof of Stake is a nice concept. Its like buying 51% of a company and then crashing it into a wall.

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

#39

Post by Klathmon »

naveen99 wrote: post #31
pietjepuk88 wrote: post #25

Earlier quoted context omitted.

The most typical way to profit from this, is to have quite a bit of ETC, and then sell it on an exchange or buy something expensive. This transaction would then end up on the block chain, and eventually be considered secure / part of history. Privately, you are building a chain where said transaction did _not_ occur. Because your hash rate is high enough, you are generating blocks at at least the pace of the public c…

so to be safe, an exchange should require more confirmations depending on size of deposit. Basically the number of confirmations you could finance an attack for with the deposit.

Yes, and most do. Many will semi-routinely increase the number of confirmations during times where it could be necessary (like chain splits or network upgrade events), or adjust the number of confirmations depending on the size of the currency and overall usage.

Another mitigation is to shut down trading until the attack is over. Maintaining a 51% attack is expensive (assuming there is at least SOME usage of the coin), and if you just say "we won't be doing business for the next 24 hours", the attacker now has to maintain that attack for the next 24 hours, and if the company wants, they can just extend the time. Eventually (hopefully!) the attacker will run out of money, and the "correct" chain will take it over again.

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

#40

Post by CydeWeys »

johndunne wrote: post #7

This is inevitable. Ethereum Classic (ETC) isn't the only currency such attacks have been successful on. The site https://www.crypto51.app/ puts the cost of running a 51% attack on ETC at ~$5k per hour. The incentive for running these attacks for profit becomes higher as the market cap of these coins increases, making long-term 'investment' in these coins nonsensical.

If you're not on the largest coin for any particular interchangeable hashing algorithm then you're susceptible to these attacks, as people from a larger coin could simply turn their hardware against you and take you out.

That means: For SHA256^2-specific hardware, Bitcoin (the real one, not Cash, Gold, or SV), for scrypt, Litecoin, and for anything mined on GPUs, Ethereum (not Classic).

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