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This is inevitable. Ethereum Classic (ETC) isn't the only currency such attacks have been successful on. The site https://www.crypto51.app/ https://www.crypto51

• NathanCH 8y ago
  Some of these numbers are very low. $30/h for Bitcoin Private? Seems inexpensive, what am I missing?
  • brianwawok 8y ago
    No one uses it. So you attack it. Cool. You can't turn it into USD or anything else, so you just spend $30 for nothing.
    • IncRnd 8y ago
      And, that's exactly why it only costs $30.
    • matte_black 8y ago
      But you still get the prestige of having taken down a coin.
      • baddox 8y ago
        What makes you think there would be any such prestige earned?
        • matte_black 8y ago
          It’s not very often you get a chance to take down a currency. In 30 years from now you’ll be able to brag about how back in your day you took down entire cryptocurrencies with 51% attacks.
          • vasilipupkin 8y ago
            51% attacks are quite possibly wire fraud so I would refrain from bragging about them. More accurately, trying to double spend the coins is wire fraud.
            • AlexCoventry 8y ago
              Not if you have the consent of the counter-parties (or are the counter-parties.) It might be against some other law to manipulate the price like that, though.
            • matte_black 8y ago
              Which government will prosecute?
              • rando444 8y ago
                The person they are swindling can go through their own authorities, and if the authorities in the criminal's country are alerted to his activities, they can go after them as well. Theft and fraud don't take on different meanings just because the currency is digital.
                • matte_black 8y ago
                  So basically it sounds like you'll never get caught.
          • deleted 8y ago
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          • brianwawok 8y ago
            In 30 years no one will use crypto and people that invested in crypto will be laughed at.
      • stale2002 8y ago
        "prestige" is exactly what smart criminals are attempted avoid. "Prestige" is how people end up in jail, or otherwise...
    • xur17 8y ago
      It's listed on several exchanges [0], so assuming you can carry out the attack, you could pretty easily profit. Not a ton of volume, but you could make some money. [0] https://coinmarketcap.com/currencies/bitcoin-private/#markets https://coinmarketcap.com/currencies/bitcoin-private/#market...
  • johndunne 8y ago
    You're not missing anything. The coins are literally worthless other than to those who trade them on crypto exchanges, to steal each other's lunch money. Plus, launching an attack isn't just a case of paying $30 per hour. You need to have a client able to perform whatever your aim is for the attack, which requires a level of coding knowledge. And dev's at that level of knowledge are probably earning real money for their time.
    • deleted 8y ago
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• semi-extrinsic 8y ago
  How can there be coins with $5M+ market cap where the cost of a 51% attack is $3.00 ?? In an efficient market, thieves should just immediately attack that. Or is the benefit too low?
  • ceejayoz 8y ago
    There's no demand for those coins. $PAC may have a $5M market cap, but it had $6,500 in volume in the last 24 hours. Some (most?) of that volume is likely to be people just moving stuff around rather than actual buying/selling between people. You might get rich on paper, but good luck getting anyone to help you convert your riches into spendable currency.
    • nickik 8y ago
      That's why Proof of Stake is a nice concept. Its like buying 51% of a company and then crashing it into a wall.
    • yreg 8y ago
      But even for the top currencies, it is quite cheap. Ethereum 51%/h for 106k? Wouldn't the attacker be able to get much more out of it?
      • ceejayoz 8y ago
        That should tell you just how thin the order books actually are, despite the supposedly enormous "market caps".
      • CydeWeys 8y ago
        The thing is, the amount of GPU processing power required to attack Ethereum is not readily available, and certainly not at a cost of only $106k. That $106k figure comes from extrapolating out marginal rental cost of a single GPU, never mind that there aren't enough GPUs rental to overwhelm the whole network. To give you an idea, the overall Ethereum network is currently 190 PH/s, so you'd need significantly more than that to have a high chance of launching a short term attack with reasonable success rate (if you only control 51% then your odds actually aren't great). Let's say you need 300 PH/s. Well, the average modern AMD graphics card that is suitable for mining Ethereum only does around 30 MH/s. That means that you need 10 million such graphics cards. They simply aren't available for rental anywhere at such scale. That's why you're not seeing such an attack happening. The raw monetary figures are misleading.
• CydeWeys 8y ago
  If you're not on the largest coin for any particular interchangeable hashing algorithm then you're susceptible to these attacks, as people from a larger coin could simply turn their hardware against you and take you out. That means: For SHA256^2-specific hardware, Bitcoin (the real one, not Cash, Gold, or SV), for scrypt, Litecoin, and for anything mined on GPUs, Ethereum (not Classic).
  • lvs 8y ago
    A defense against this is merged mining (e.g. Dogecoin and Litecoin, Namecoin and Bitcoin).
  • sp332 8y ago
    people from a larger coin could simply turn their hardware against you and take you out. Only at the expense of leaving their coin more vulnerable to a similar attack.
    • CydeWeys 8y ago
      Not if you're much larger than the alternatives, which tends to be the case.
      • kuhhk 8y ago
        Or they could just hop amongst 50 $smallCoins, destroying each, before jumping back into BTC/ETH. Thereby destroying all $smallCoins and driving users into $bigCoin
    • deleted 8y ago
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    • garmaine 8y ago
      Not until the difficulty adjusts, and the attack takes less time than that to execute. And they'd have to be equally sized to actually leave the other coin vulnerable in any case, not asymmetric as in this case.
  • 8y ago
• dragontamer 8y ago
  > The incentive for running these attacks for profit becomes higher as the market cap of these coins increases, making long-term 'investment' in these coins nonsensical. I disagree that market cap is the primary indicator. Note that market cap (or really, price of ETC on major exchanges) has dropped dramatically in the past 3 to 6 months. So Market Cap / Price of ETC is a minor factor. In contrast: the ABSOLUTE COST of a 51% attack drops each time the difficulty drops. That's what I personally think is the main contributor here, because the market-caps of all coins have dropped dramatically the past few months. In effect: its not so much that the potential profit out of a hypothetical 51% has gone up (it hasn't: Ethereum Classic is way cheaper than it used to be). Its that the DIFFICULTY of ETC has dropped dramatically, finally making the 51% profitable.
• danra 8y ago
  Really surprised by the relatively low cost of attacking Bitcoin with 51% for one hour - claimed to be about $300k. Is this number for real? I can think of many actors for whom this is just small change, and who might have incentive to break trust in the Bitcoin network by successfully performing such an attack.
  • tgsovlerkhgsel 8y ago
    I believe the number assumes that you can get hashpower at the current price for (a small amount of) hashpower. However, as demand increases, the price goes up, making the attack more expensive in practice. Also, if people notice what you're doing, they'll probably stop selling hashpower to you (since you're attacking what makes their hardware valuable), driving your costs up further.
  • tokai 8y ago
    That is a really low cost. That's within crowdfunding territory. If a potato salad could make it big, why not fund a major event in web history? I'm thinking stretch goals like t-shirts and mugs.
  • baddox 8y ago
    Seems like it would be very difficult to make back your $300k with a double-spend in one hour, based both on my intuition and the fact that it doesn't appear to be happening.
    • michaelmrose 8y ago
      If I'm reading it correctly you need 600k to have a 50/50 chance at double spending. So say you acquire 500k in bitcoin and you spend $600k to have your chance to double spend the 500k. Assuming your $600k in mining actually gets you $600k in bitcoins mined the expected result is. 50% chance spend 1.1 million get 1.1 million back minus substantial overhead. Say 10% overhead although I have no idea what the actual overhead would be. So negative 100k. 50% chance spend 1.1 million + 100k overhead get 1.6 million back. Net gain of 400k So average gain of 200k assuming you can find a market to move that much bitcoin that quickly and always assuming your creativity isn't rewarded with jail time. People with substantial resources can find way to make money that are repeatable and don't involve finding new and exciting ways to go to jail.
• bouncycastle 8y ago
  The tweet mentioned that it was a "chain reorganization". These happen all the time, even in Bitcoin, by design. The simplest way to defend against these is just to wait for more confirmations to arrive, thus making an attack more expensive. Many exchanges require a lot more confirmation for some of these smaller market cap coins.
• lukifer 8y ago
  Yet another reason why Proof of Stake is destined to outcompete Proof of Work. ;)
  • garmaine 8y ago
    Proof of Stake is a perpetual motion machine. You can't safely tie consensus to something (stake) which is determined by consensus. That's circular reasoning and ungrounded.
    • drb91 8y ago
      What would failure look like?
      • garmaine 8y ago
        A system that has effectively bifurcated with conflicting chain tips caused by rewriting history with new nodes unable to tell which is original, or a fully centralized stake-mining where a subset of stake voters game the system to unfairly select themselves out of proportion of their stake weight.
        • koheripbal 8y ago
          Is that reeealy so different from a PoW fork?
          • garmaine 8y ago
            A proof-of-work fork is an unstable situation, resolved when more work is applied to one side vs the other, which inevitably happens without active intervention. A proof-of-stake fork is permanent--someone new to the network has no built-in mechanism for deciding which side to prefer: they both seem equally valid. A properly constructed proof-of-work mechanism has no built-in mechanism for a malicious minority hash power to take control of the protocol, shutting out the higher hash rate majority from mining blocks.
    • 8y ago
• philwelch 8y ago
  I wonder if there's a formula for the maximum wallet or transaction size you can safely have on a particular cryptocurrency given the cost of a 51% attack. If a 51% attack costs $5,000 per hour, you're only going to do it if you can extract more than $5,000 of value (or if your motivation is to see the world burn). In theory you might be able to set things up such that the cost of a 51% attack is necessarily greater than whatever financial gain you could get from it.
  • schoen 8y ago
    Budish (2018) gives some attempts at formulas to determine attackers' incentives under various hypotheses: http://faculty.chicagobooth.edu/eric.budish/research/Economic-Limits-Bitcoin-Blockchain.pdf http://faculty.chicagobooth.edu/eric.budish/research/Economi... It's tricky to directly apply these to cryptocurrency adopters' risk, although they apply more directly to "transaction size" than to "wallet size". You can probably apply some of Budish's calculations to transaction size unless you anticipate there's a way that your transaction counterparty could be defrauding you and other people in roughly the same way at roughly the same time. (For transaction size, the main risk is that you give someone something else of value in exchange for a transaction that's subsequently removed from the consensus history.) But for wallet size, the risk is not that someone steals your cryptocurrency from your wallet, but that your cryptocurrency becomes less valuable because other people recognize risks more immediately as a result of discovering and publicizing a successful attack. But that has most to do with how other people respond to the news of the successful attack, which is harder to predict.
    • philwelch 8y ago
      > But for wallet size, the risk is not that someone steals your cryptocurrency from your wallet, but that your cryptocurrency becomes less valuable because other people recognize risks more immediately as a result of discovering and publicizing a successful attack. But that has most to do with how other people respond to the news of the successful attack, which is harder to predict. And that's going to be governed by irrationality, especially given the irrationally exuberant bubble effects of the cryptocurrency market in the first place. But once that wears off...I don't know. If you somehow managed to make a cryptocurrency that couldn't be profitably attacked, and made the base minimum cost of such an attack high enough, you'd still be vulnerable to a state-level adversary, but every system is vulnerable to a state-level adversary.