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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?

#41

Post by csomar »

glofish wrote: post #21

It feels surprisingly cheap. Take bitcoin, a 105Billion cap can be subverted for just 700K per hour? Not to mention DeepOnion for 3 bucks an hour. I can see people do that just for lulz.

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 rent half of bitcoin mining rate. So such an attack will be order of magnitudes more expensive if even possible.

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

#42

Post by skitout »

yodsanklai wrote: post #29
skitout wrote: post #25

Earlier quoted context omitted.

The market cap does not fit into the equation on how an attack works ; it just gives you idea on how big/small is this blockchain Blockchain don't have a centralized entity to "validate" and secure each transaction, so had to come with a solution to securely do so in a decentralized manner... Most blockchain use Proof of Work to do so : to participate on the validation process you have to "pay", by working on some ma…

But if it costs only $3 to break the system, how come the market cap is so high?

This is enough to do some double spending (= you won't get much here!)... if no one is noticing (if hey notice they can increase the cost / decrease the reward).

I guess some people still think DeepOnion have potential in the future...

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

#43

Post by pat2man »

yodsanklai wrote: post #17
pat2man wrote: post #4

Since it took a while for me to understand this. A 51% attack doesn’t let you steal money from anyone. It essentially lets you block all transactions from making it to the blockchain. Nodes will still verify all transactions and ignore transactions that are invalid. Edit: you can also create multiple forks and switch between them. External viewers will see both forks and if they don’t or can’t handle the difference t…

My understanding is that the goal is double-spending. The attacker will make a transaction to a victim. The victim would be convinced it owns the coins, as the transaction appears in the chain. The attacker will then start mining a new chain (starting at a block before the transaction) which does not contain the transaction to the victim. If the attacker has enough computing power, it will be able to make the new cha…

Yeah. Is the part where they are convinced that is the actual double spend.

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

#44

Post by SkyMarshal »

ecwilson wrote: post #23
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…

I was actually shocked that it could be this low and thought it must be wrong. Other sources have suggested it would cost over $1B: https://u.today/guides/blockchain/bitcoin-51-attack-how-it-w... > The hash rate is currently about six exahashes per seconds. Considering the most efficient ASIC miner with a hash rate of about 13,000 GHS (using the SHA-256 algorithm) being sold for about $2,100, an attacker will require…

I think the site assumes you already have the hardware, and is just calculating the OpEx of the attack, not the CapEx. Like, if a major mining pool decided to 51% attack a coin.

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

#45

Post by caymanjim »

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…

$705k/hr is so low as to be unbelievable. You need to at least temporarily out-compute everyone else in the world, and there's a lot of horsepower behind Bitcoin.

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

#46

Post by billions »

skitout wrote: post #5

1) If a big crypto-community notices an attack, the cost of a 51% attack would rise 2) There are mechanisms to offer smaller cryptocurrencies Bitcoin level security, like Komodo's Delayed Proof of Work ( https://komodoplatform.com/security-delayed-proof-of-work-dp... )

The number of transactions that can be altered from a sustained 51% attack would be so few and recent (last 10 minutes) in comparison to cost that it makes it not worth it

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

#47

Post by seibelj »

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

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

#49

Post by tromp »

Retric wrote: post #28
pat2man wrote: post #4

Since it took a while for me to understand this. A 51% attack doesn’t let you steal money from anyone. It essentially lets you block all transactions from making it to the blockchain. Nodes will still verify all transactions and ignore transactions that are invalid. Edit: you can also create multiple forks and switch between them. External viewers will see both forks and if they don’t or can’t handle the difference t…

A presumably legal and profitable 51% attack can be to simply ignore other miners. Effectively someone with 45% hashing power get’s 45% of the block rewards + fees. However someone with 55% hash power can get 100% of the rewards plus fees a significant bonus. Alternatively, double spends let someone sell the same coins to multiple people though at legal risk for doing so while also theoretically collecting all block…

> However someone with 55% hash power can get 100% of the rewards plus fees a significant bonus.

Note that, until the 2-week boundary where difficulty adjusts, they only get 100% of the roughly 45% less frequent rewards, since the 45% orphan rate will slow down overall progress.

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

#50

Post by meowface »

hn_throwaway_99 wrote: post #26
glofish wrote: post #21

It feels surprisingly cheap. Take bitcoin, a 105Billion cap can be subverted for just 700K per hour? Not to mention DeepOnion for 3 bucks an hour. I can see people do that just for lulz.

The issue with saying how much a 51% attack "costs" is that ALL cryptocurrencies (and, really, ANY currency) is just based on the trust that the currency has "value", meaning that it would be accepted as payment for real goods and services. A 51% attack on bitcoin would be easily noticeable. If a 51% attack was really "viable", it means that essentially bitcoin would have $0 value, because all of its value is based o…

How would the community collectively agree to ignore the rogue chain in a timely fashion? If a client announcement is sent out, that'd help, but there'd still be a lot of people stuck on the original chain (for example, some people on vacation or something). For at least a few days, there'd probably still be a lot of trust to capitalize on, and they could possibly get away with a few big heists (e.g. making a big purchase with BTC and then reversing the transaction after you've received the items).

Also, if the community does ignore the rogue chain, what's to stop the attackers from switching their attack to the other non-rogue chains as soon as they seem to gain traction? If they can hypothetically reliably sustain 51%+ power for weeks, they could potentially perform a DoS on an entire currency. And you're right, Bitcoin would probably soon reach close to $0 (though would probably slowly bounce back once/if the attack seems to be permanently thwarted).

If I'm understanding your last sentence right ("probably boost other existing resources to back it out"), then I also think that'd be the most likely scenario. A serious sustained 51% attack (lasting beyond several days) would turn into a Dragonball Z-like battle, with both sides firing continuous energy beams at each other in parallel. Each side would be trying to increase the magnitude of their beams to keep the other side's beam from collapsing theirs. I think the legitimate mining team would have a lot more energy in reserve (e.g. good samaritans who start mining for the first time to help push away the attackers - kind of like Goku's Spirit Bomb, which Frieza can't replicate) and would probably win. However, if for some reason the attackers can win for weeks at a time, then it'd be a serious DoS.

Disclaimer: I might be misunderstanding something important here. Not a cryptocurrency expert whatsoever.

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