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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

#51

Post by pietjepuk88 »

sf_rob wrote: post #44
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…

Upvoted for explaining the attack well but RE:longest chain, Blocks are added at a standard rate so the chain with the greatest accrued work is the "truth".

You are totally correct :) I figured it would be easier to forgo the explanation of "difficulty" and difficulty adjustments (which ETC/ETH do much quicker than e.g. Bitcoin does).

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

#52

Post by orblivion »

makomk wrote: post #33
orblivion wrote: post #11

Earlier quoted context omitted.

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.

Hmm. The humans at the exchanges seem to be able to tell the difference. I wonder if it could be encoded.

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

#53

Post by ajkjk »

I'm not sure I think the word 'attack' is right here. Crypto by design says that if anyone controls over half the network, they get to say what happens. Sounds like democracy, specifically the 'tyranny of the majority': over half the network votes that they get more of your money, so they do!

Of course if you're in the other 49% you might feel attacked, but ultimately this is working as intended.

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

#54

Post by theamk »

albertgoeswoof wrote: post #29
kryogen1c wrote: post #21

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. 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…

There are some cool things you can do with blockchains, they’re just a little over hyped. It’s pretty neat to send funds to someone without going via a 3rd party, it’s cool to run code on a global computer, it’s awesome to have digital assets that can’t be doled out on a whim by a central authority.

... It's great when you can lose lots of money by spilling soda on your computer?*

*more money than this computer's price

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

#55

Post by pryce »

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?

Other people have answered this from a more technical perspective.

Philosophically, what the distributed blockchain is, is an agreement for adjudicating whose record (eg list of transactions) should be agreed on as "the valid one". If you already have a different, reliable external way of deciding this question, that is (arguably) conceding that you didn't need a distributed blockchain in the first place.

EDIT: I've realised my comment could be misinterpreted as endorsing the blockchain 'movement'. I am among those who are quite skeptical of these many blockchain projects.

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

#56

Post by CWuestefeld »

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…

Of course, doing this only makes sense if what you gain outweighs the costs of performing such an attack.

If the hardware to accomplish the attack is available for your use, the cost of the mining should net out at zero-ish, because you're also getting the rewards for doing the mining. So the net cost of the attack is just the overhead for the mining hardware.

Coincidentally, economist Alex Tabarrok just wrote about this today: https://marginalrevolution.com/marginalrevolution/2019/01/bi...

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

#57

Post by pslam »

ajkjk wrote: post #53

I'm not sure I think the word 'attack' is right here. Crypto by design says that if anyone controls over half the network, they get to say what happens. Sounds like democracy, specifically the 'tyranny of the majority': over half the network votes that they get more of your money, so they do! Of course if you're in the other 49% you might feel attacked, but ultimately this is working as intended.

The intent is a currency which can be reliably used for exchange of goods and services. This would seem to cause a failure of the basic reason for its existence.

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

#58

Post by stcredzero »

shaki-dora wrote: post #46
stcredzero wrote: post #17

Earlier quoted context omitted.

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... The above part pretty much applies to humanity as a whole, going back at least 200k years.

Yeah, except a good portion of the errors made in those 200k years at least had the excuse of being new . Blockchain stands apart as repeating every single problem the financial system solved over the last 300 years, while being driven by a community best defined by their arrogant dismissal of that very financial system they are reinventing, piece-by-piece. Turns out civil society (i. e. laws, courts, institutions, e…

Yeah, except a good portion of the errors made in those 200k years at least had the excuse of being new.

Blockchain stands apart as repeating every single problem the financial system solved over the last 300 years

Forgetting then repeating the mistakes of the past is yet another long standing hallmark of human beings. In every age, in every place, the deeds of people remain the same.

Turns out civil society (i. e. laws, courts, institutions, economics, shared fictions of value, and trust) cannot actually be replaced by an...

An algorithm. A new religion. A new social theory. A new lifestyle. A new understanding...

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

#59

Post by Klathmon »

jeremyjh wrote: post #50
Klathmon wrote: post #39

Earlier quoted context omitted.

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…

The attack cannot be observed until it is accomplished. Naturally the chain will be long enough to target the exchange the spend was made at.

it can't be observed until it's acted on, but it may not be done after the first "attack", especially if it's cheap enough to launch on that specific coin.

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

#60

Post by zeroname »

semi-extrinsic wrote: post #22
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.

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?

The only way to profit is to double-spend, so you'll have to buy or already own a substantial amount of those junk coins and then sell them. After you performed the attack, those coins that you now could theoretically sell again may be suspended from trading or should at least trade at a substantially lower price.

Add in the opportunity cost of exercising such an attack and it's not clear that you could turn a profit.

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