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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?

#81

Post by RL_Quine »

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

A GPU is an ASIC, which can mine RandomX. The idea that you could make something that's able to only be computed by a general purpose GPU, and not something more specialized, is just absurd. Even if that's just removing the unnecessary display hardware from the GPU and whatever parts of the shaders aren't being used, you still have an advantage.

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

#82

Post by [deleted] »

cs702 wrote: post #61

By definition, to execute a 51% attack on Bitcoin, you would need to buy computing power greater than 100% of the entire network's current computing power. In other words, you would single-handedly double the global demand for computing power in this market . Is there enough supply readily available to satisfy a doubling of global demand? How much would it cost to bring such computing power online? How quickly could…

[deleted]

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

#83

Post by GuB-42 »

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.

For all the big cryptocurrencies, the price assume that you can buy unlimited hashing power if you have the money. That's obviously not true. Once you have rented all available hardware, having more money to spend won't help.

That's what the "NiceHash-able" column is for. To put it simply, if it is less than 100%, you are going to have trouble renting enough hashing power, and conducting the attack will be impossible in practice, or at least much more expensive than the listed price.

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

#84

Post by RL_Quine »

SilasX wrote: post #78
RL_Quine wrote: post #68

Earlier quoted context omitted.

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.

All miners connect to pools using a protocol called stratum. This is JSON piped over TCP with newline terminations. There is no authentication for this protocol and no encryption. You can simply intercept the communication here and have all the miners on a pool actually mine for your replacement pool, and nobody will ever catch on until its far too late.

> 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.

That's not correct in practice. There's no authentication of the work going to the miner at all, so an attacker can just change the destination before the miner even sees the work.

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

#88

Post by gambler »

RL_Quine wrote: post #69
gambler wrote: post #51

Computational power is not a good proof of anything. It devours energy and disproportionately rewards weird market actors (like people with custom mines ASICs). I always wondered whether storage could be used as proof of stake. It might use less energy and it probably will have much better effect on the IT industry as a whole. First, mining ASICs are not general computational devices and cannot be used for anything u…

> Computational power is not a good proof of anything. It devours energy and disproportionately rewards weird market actors (like people with custom mines ASICs). It's literally what it says it is, proof of work. Consumption of electrical power in a way that can't be re-used for anything else. > If you want to transact with someone, they send you a challenge that consists of a set of addresses in a large file. You mu…

> I'll cheat by making my "large file" the output of a PRNG, meaning I don't have to store any of it, but other people do because they don't know the seed.

This will work, but only until the file is sufficicently changed/expanded by the networks as the result of transactions.

(I probably should have said it explicitly: the file would be shared by all participants.)

You can also generate the file by recording something random everyone can observe, like records of a stock market, temperature of some location, etc. I don't see any reason it would have to be perfectly, cryptograhically random.

And yes, a single participant could "help" other nodes by responding to challenges instead of them. But think about the economics of how that would work over time.

I'm not saying that what I described is a full, working, tamper-proof protocol, but I think something interesting can be built based on the core idea.

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

#89

Post by RL_Quine »

exdsq wrote: post #74
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?

AWS and Azure would be using CPUs, GPUs, and FPGAs, which have nowhere near the sort of speeds as dedicated hardware. It's something in the order of a trillion desktop CPUs to equal the same hashrate as the bitcoin network is currently.

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

#90

Post by bufferoverflow »

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.

That's not how any of this works. There's no massive mining traffic. Most of the mining is done in private data centers. They only broadcast their transactions when they "solve" the hash.
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