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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

#191

Post by lkdjjdjjjdskjd »

labster wrote: post #175
dragontamer wrote: post #128

Earlier quoted context omitted.

51% attackers mine in secret. Basically, you spend your coins today, while controlling a 51% share. When everyone else's 49% hash-power creates 98 blocks, your 51% share will create 102 blocks. But secretly. That's the key. Now that your chain is +4 ahead (or wait even longer and become +10 ahead), you can spend your coins on the public chain. Then, you publish your 102 alternative blocks (which barely adds any hash…

If only we had a currency that was immune to 51% attacks because a government was willing to use force to preserve its value, and therefore doesn't need a massive use of energy for its proof of work.

Maintaining that force also costs a lot of energy. Abnd such a currency doesn't do the same things as crypto currencies.

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

#192

Post by askmike »

thaumasiotes wrote: post #190
speakeron wrote: post #188

Earlier quoted context omitted.

> These statements directly contradict each other. They don't contradict each other at all. > Once block 26 comes online, block 6 is a permanent feature of the blockchain. What defines the 'blockchain'? It's the chain with the most work. Outside of a centralized checkpointing mechanism, the only definition of the valid blockchain is the one with the most work behind it.

>> These statements directly contradict each other. > They don't contradict each other at all. 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. > What defines the 'blockchain'? It's the chain with the most work. No, it's the chain accepted by a group of min…

> 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 they require 6 confirmations per transaction before they credit it?

> 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).

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

#193

Post by kordlessagain »

askmike wrote: post #178
labster wrote: post #175

Earlier quoted context omitted.

If only we had a currency that was immune to 51% attacks because a government was willing to use force to preserve its value, and therefore doesn't need a massive use of energy for its proof of work.

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…

Splitting the network causes it to become a marketing problem.

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

#195

Post by aiCeivi9 »

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…

People reacted in so irrational ways to any BTC news related to crypto (the "this is good for bitcoin" meme), that I am not sure if it would crash the price. On hte other hand a "bank run" on attacked exchange is likely. And the victim of attack will almost always be the exchange. BTW no matter what crypto fans claim ("code is law") getting anything from a service and then canceling transaction that paid for it by 51% attack will be a criminal act under many jurisdictions. Considering that shorting crypto is probably better solution. Thought I am not sure if it is even possible to borrow required amount of coins.

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

#196

Post by rspeer »

stcredzero wrote: post #58
shaki-dora wrote: post #46

Earlier quoted context omitted.

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. l…

This comment sounds like Erlich Bachman on Silicon Valley.

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

#197

Post by thaumasiotes »

askmike wrote: post #192
thaumasiotes wrote: post #190

Earlier quoted context omitted.

>> These statements directly contradict each other. > They don't contradict each other at all. 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. > What defines the 'blockchain'? It's the chain with the most work. No, it's the chain accepted by a group of min…

> 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 confirmed.

As far as I can see, this is just a design mistake. (And equivocating over the meaning of "confirmed".) The current system never treats any block as confirmed. The only statuses a block can have are "invalid" and "provisionally accepted". There is no "accepted" status, and a valid block may be revoked at any time, no matter how long it may have been valid for.

But there's also no reason not to have an "accepted" status, and to reject candidate blockchains which alter accepted blocks. This should be part of the mining protocol. Treating it as non-binding advice to merchants misses the point.

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

#198

Post by nearbuy »

thaumasiotes wrote: post #190
speakeron wrote: post #188

Earlier quoted context omitted.

> These statements directly contradict each other. They don't contradict each other at all. > Once block 26 comes online, block 6 is a permanent feature of the blockchain. What defines the 'blockchain'? It's the chain with the most work. Outside of a centralized checkpointing mechanism, the only definition of the valid blockchain is the one with the most work behind it.

>> These statements directly contradict each other. > They don't contradict each other at all. 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. > What defines the 'blockchain'? It's the chain with the most work. No, it's the chain accepted by a group of min…

I don't follow. Even if the current group of miners decided older blocks are irrevocable, if there was a prolonged 51% attack, it would mean the majority of miners would be saying, "Hey, those confirmed blocks... that's not what actually happened. Look, here's the real history, with the real confirmed blocks."

And then everyone else on the network would say, "Crap, who should we believe? Let's go with the majority." And the attack would win.

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

#199

Post by antocv »

vkou wrote: post #63
wcoenen wrote: post #62

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. Yes. But it's the same for the market cap of company stocks. So saying that "the market cap isn't truly $5M" is missing the point a bit. The market cap can truly be $5M without $5M having been invested. That's just not what market cap means.

No, this is precisely why trying to calculate the market cap of a crypto-currency is pointless. A company is a productive enterprise, that produces value for you, if you sit on shares of it. Something like bitcoin is a purely speculative instrument, that produces no value if you sit on it. The market cap for a company is an imprecise proxy for all expected revenues, discounted by time[1]. The market cap for a currenc…

> A company is a productive enterprise, that produces value for you

Hmm, does this mean Boeing, Saab Aerospace, the ammo factory is also a productive enterprise, which produces value for me? The bombs dropped on people in sandals in Yemen, how is that producing value for anyone owning the stock of war companies? Also owning said stock indirectly through pension funds.

How many companies are not in any definition "productive" and end up bankrupt, restructured or just bailed-out?

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

#200

Post by Robin_Message »

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…

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, confirmations are there for vendors to be sure a few blocks weren't mined at the same time, but they do nothing against a 51% attack.

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