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Cost of a 51% attack for different cryptocurrencies?

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Re: Cost of a 51% attack for different cryptocurrencies?

#71

Post by joosters »

InvaderFizz wrote: post #65
joosters wrote: post #52

Earlier quoted context omitted.

You can do much better than that! The simplest way to profit from a 51% attack is to send some coins to a crypto exchange, wait for the required 'n' blocks to confirm your deposit, then 51% attack the chain to remove your original payment. At the same time, you can either withdraw your ill-gotten coins from the exchange, or trade them for something else and withdraw onto a different blockchain entirely. This mechanis…

This would require funding, exchanging, and double spending all in the span of a few minutes. The more confirmations you have to unwind, the more work you have to do to catch up with the long chain. All that will happen is exchanges require a greater number of confirmations before allowing you to trade deposits.

All true, but it is exactly what happened in this latest attack!

And yes, reportedly exchanges have increased the number of confirmations required to confirm a deposit as a result. But it's too late for the ones who got ripped off by the double spend!

Re: Cost of a 51% attack for different cryptocurrencies?

#72

Post by qertoip »

hudon wrote: post #34

If you're capable of playing a long con, it costs much less than the stated dollar prices. With Bitcoin, for example, a smart malicious actor could infiltrate the Core development team and through their social capital make certain malicious pull requests get merged. This way, if the chain ever splits (let's say, due to a bug you planted), you can actually also influence miners to hop onto a minor chain without you ev…

The double spend is only possible against specific counter-party, for example an exchange or a merchant.

For very large value transfers exchanges are expected to wait for 100 confirmations (~17 hours) until they credit balance.

It's all probabilistic.

Finally, Bitcoin PoW is not security theatre, it is just one piece of the complex security system.

Re: Cost of a 51% attack for different cryptocurrencies?

#73

Post by jandrese »

seibelj wrote: post #47
rocqua wrote: post #32

As I recall, last time this was posted, Monero was still on this list. Now it is not. Did the new PoW algorithm for Monero essentially remove the 'rentable hashing power' available?

There are no ASICs known to work on Monero anymore. As a brief summary, the new algorithm (RandomX) uses a bespoke virtual machine that requires 2GB of memory, and programs are randomly generated until the opcodes take in an input (previous block hash) and have an output (new hash with required difficulty) that pass the requirements. It is very interesting. https://github.com/tevador/RandomX

That sounds fantastically complex. I don't know anything about Monero but I'm already wary that there might be a way to hack the VM to spit out hashes without doing as much work as a stock VM.

Re: Cost of a 51% attack for different cryptocurrencies?

#74

Post by exdsq »

TekMol wrote: post #3

$705k per hour for Bitcoin - these numbers sound very expensive. Do they take into account that during an attack the attacker will earn block rewards and transaction fees? Because if not, then they vastly overestimate the costs. This sounds like it is based on the some energy price that would be needed to do 51% of Bitcoins hashing. Doing so could very well be profitable. The reason it would be hard to do is that the…

There's no way I believe $705k would work. The company they're pricing that off of don't have the computational ability to run a 51% attack. I'd be interested to know how the entire power of the bitcoin network compares to say AWS or Azure?

Re: Cost of a 51% attack for different cryptocurrencies?

#75

Post by pat2man »

7777fps wrote: post #54
pat2man wrote: post #12

Earlier quoted context omitted.

It’s an eventually consistent system, so you can defraud people who don’t take that into account. But internally it will always be consistent.

And by "don't take that into account" you mean "transact anything off chain" including other currencies, goods, services, etc.

You can transact off chain. You just have to calculate the likelihood that your transaction will go through, and adjust accordingly. The cost of a 51% attack for 24 hours is a lot higher than the cost for one hour, so if you want for 24 hours the likelihood goes way up.

Re: Cost of a 51% attack for different cryptocurrencies?

#76

Post by csomar »

joosters wrote: post #52
csomar wrote: post #41

Earlier quoted context omitted.

The thing is, what you can do with a 51% attack is very limited and the big services are probably going to be aware of it. Best case scenario is that you halt transactions for a few hours. This will cost a few million dollars with, maybe, no possible reward. The next problem is that this calculation is based on the current hash-rate cost. However, you don't have that much hardware and it'll be close to impossible to…

You can do much better than that! The simplest way to profit from a 51% attack is to send some coins to a crypto exchange, wait for the required 'n' blocks to confirm your deposit, then 51% attack the chain to remove your original payment. At the same time, you can either withdraw your ill-gotten coins from the exchange, or trade them for something else and withdraw onto a different blockchain entirely. This mechanis…

From my understanding this is not a 51% attack but rather a chain-rewrite which require significantly way more hash rate than the bitcoin network has. (which is why exchanges consider 3-6 confirmations as the safe number).

Re: Cost of a 51% attack for different cryptocurrencies?

#77

Post by bduerst »

InvaderFizz wrote: post #65
joosters wrote: post #52

Earlier quoted context omitted.

You can do much better than that! The simplest way to profit from a 51% attack is to send some coins to a crypto exchange, wait for the required 'n' blocks to confirm your deposit, then 51% attack the chain to remove your original payment. At the same time, you can either withdraw your ill-gotten coins from the exchange, or trade them for something else and withdraw onto a different blockchain entirely. This mechanis…

This would require funding, exchanging, and double spending all in the span of a few minutes. The more confirmations you have to unwind, the more work you have to do to catch up with the long chain. All that will happen is exchanges require a greater number of confirmations before allowing you to trade deposits.

And most exchanges require numerous confirmations for this reason.

Re: Cost of a 51% attack for different cryptocurrencies?

#78

Post by SilasX »

RL_Quine wrote: post #68
Meekro wrote: post #60

There is absolutely no way to 51% attack a major coin like Bitcoin for as little as $700k an hour. They are extrapolating from Nicehash's mining rental prices, but Nicehash doesn't have anything like the capacity you'd need. You can see here[1] that nicehash has about 500 PH/s (500,000 TH/s) available for rent. However, Bitcoin's total hash rate right now is 100,000,000 TH/s[2]. This means that if you rented out the…

Why are you assuming that hashrate would be obtained legally? If you're already assuming criminality, go all out! BGP route hijack the unencrypted, unauthenticated mining traffic and call it your own. Cost is basically nothing to do so, other than some jail time.

Can you clarify what you mean by hijacking mining traffic? If you mean the traffic of mining pools communicating their solutions to the pool's "mother brain", those are already cryptographically attached to a solution that pays out to specified addresses. You can't substitute the transactions in the block/solution without redoing the PoW.

That's why miners can't steal a pool's solutions to begin with.

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