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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?

#61

Post by cs702 »

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 it be done? Wouldn't the price of computing power skyrocket?

EDIT: Meekro's comment elsewhere on this page makes essentially the same point in a more concrete manner: https://news.ycombinator.com/item?id=22161500 -- I think his comment is better; read it. Also, see bencxr's analogy with trying to control 51% of global oil supply: https://news.ycombinator.com/item?id=22161575

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

#62

Post by WAHa_06x36 »

billions wrote: post #46
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

There are many more ways to make money off a 51% attack than just altering transactions.

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

#63

Post by urvader »

pat2man wrote: post #39
yangl1996 wrote: post #19

Earlier quoted context omitted.

It does, however, allows "double spending" attacks. In such attacks the attacker first spends a coin to buy some real goods from the victim. She then launches a 51% attack on the blockchain and "rewrites" the ledger to remove the transaction to the victim. Now the attacker gets back her money, plus the goods from the victim.

Yeah stores that accept crypto Currency need to understand this, or use an underlying abstraction that does. Of course for most chains this would make transactions very slow which is not good for commerce.

Stores that sell goods worth 700k in BTC?

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

#64

Post by WAHa_06x36 »

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…

So: Short a large amount of bitcoins, 51% attack until value plunges, earn massive amounts of money.

Of course, the problem with this is that there is no exchange that you can trust enough to actually do this.

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

#65

Post by InvaderFizz »

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…

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.

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

#67

Post by simias »

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?

Because the volume of transaction for these currencies is too low for the market cap to mean anything. Imagine if there are, say, 1 million fancycoins in existence, all owned by me. I manage to convince you to buy one fancy coin for $1. Does it means that I now have $999,999 left in fancycoins "market cap"? In theory maybe, in practice I'll almost certainly never manage to liquidate them at this price.

For these small coins like DeepOnion you'll crash the market completely if you try to sell even a moderate amount of coins. There's simply not enough demand to move a big amount of coins at this price.

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

#68

Post by RL_Quine »

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.

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

#69

Post by RL_Quine »

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 must respond with a hash of data at those addresses, problematically proving that you have the entire file.

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.

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

#70

Post by bencxr »

These numbers are based off the current price of hashrate. As soon as you try to buy significant amounts for larger currencies like Bitcoin, the numbers skyrocket.

The nice-hashable column on the site shows how much hash power is available for purchase.

To read the page naively would be a little like claiming one could hoard 51% of the oil supply given today's price at the pump. In reality, as soon as you started buying in large quantities, the price would skyrocket (making that attack very much more costly), suppliers would cut you off, and others would notice.

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