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Bitcoin Technology

Blockchain's Once-Feared 51% Attack Is Now Becoming Regular (telegra.ph) 168

Monacoin, bitcoin gold, zencash, verge and now, litecoin cash. At least five cryptocurrencies have recently been hit with an attack that used to be more theoretical than actual, all in the last month. From a report: In each case, attackers have been able to amass enough computing power to compromise these smaller networks, rearrange their transactions and abscond with millions of dollars in an effort that's perhaps the crypto equivalent of a bank heist. More surprising, though, may be that so-called 51% attacks are a well-known and dangerous cryptocurrency attack vector. While there have been some instances of such attacks working successfully in the past, they haven't exactly been all that common. They've been so rare, some technologists have gone as far as to argue miners on certain larger blockchains would never fall victim to one.

The age-old (in crypto time) argument? It's too costly and they wouldn't get all that much money out of it. But that doesn't seem to be the case anymore. NYU computer science researcher Joseph Bonneau released research last year featuring estimates of how much money it would cost to execute these attacks on top blockchains by simply renting power, rather than buying all the equipment. One conclusion he drew? These attacks were likely to increase. And, it turns out he was right. "Generally, the community thought this was a distant threat. I thought it was much less distant and have been trying to warn of the risk," he told CoinDesk, adding: "Even I didn't think it would start happening this soon."

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Blockchain's Once-Feared 51% Attack Is Now Becoming Regular

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  • Blockchain+

    Bigger, better, blockier. Just try us.
  • by CaptainDork ( 3678879 ) on Friday June 08, 2018 @11:50AM (#56750618)

    For every motherfucker out there with a computer, there's another motherfucker out there with a computer.

    The strategy for hacking blockchain is no different from hacking anything else: Learn the theory then apply the theory.

    • by Aaden42 ( 198257 )
      No, it's pretty different. Learning the theory is easy. Not really much to a 51% attack, theoretically. To apply it, you need to be the motherfucker with more computers than 51% of the rest of the motherfuckers in the world combined. You need to maintain that for several blockchain cycles to pull it off. That's a little more difficult.
      • A successful attack will also cause bad publicity and a sudden drop in value of the coin, which will hurt the attacker just as well. That's good incentive not to perform an attack.

        • by Khyber ( 864651 )

          You don't understand the speed at which these things happen on smaller blockchains. They happen fast enough for most people to simply not notice until far too late. By then, the attacker has gotten the money, made the exchange out to hard currency, and is out.

        • by jeremyp ( 130771 )

          Not if you have a short position in bitcoins.

          1. borrow bitcoins off somebody
          2. sell them to somebody else
          3. do 51% attack and make sure it is publicised
          4. buy bitcoins back at a fraction of their previous value and give them back to the person you borrowed them from

      • Then you need to read TFA. Their targets are small cryptocurrencies because these currencies still have small networks. Also, they can make money if the condition is right.

        From TFA:

        To make money using this attack vector, hackers need a few pieces to be in place. For one, an attacker can't do anything they want when they've racked up a majority of the hashing power. But they are able to double spend transactions under certain conditions.

        ...

        As such, hackers have found various clever ways of making sure the conditions are just right to make them extra money. That's why attackers of monacoin, bitcoin gold, zencash and litecoin cash have all targeted exchanges holding millions in cryptocurrency.

        By amassing more than half of the network's hashing power, the bitcoin gold attacker was able to double spend two very expensive transactions sent to an exchange.

        Through three successful attacks of zencash (a lesser-known cryptocurrency that's a fork of a fork of privacy-minded Zcash), the attacker was able to run off with about more than 21,000 zen (the zencash token) worth well over $500,000 at the time of writing.

      • by thsths ( 31372 )

        Indeed, and that is what worries me most. It seems that criminals got hold of 51% of the computing power in certain crypto systems. Maybe we need more legitimate interest?

        (And as far as I understand, you can get away with less than 51% and a bit of luck.)

  • by xack ( 5304745 ) on Friday June 08, 2018 @11:50AM (#56750626)
    The entirety of the Netherlands is growing tulips instead of food. People are prostituting them selves for chucky cheese tokens entire coal power stations being built just for funbux.

    I hope the 51%ers wreck as many cryptocurrencies as possible to crash the market so the environment can be saved, graphics cards go back to making graphics and people go back to investing into stocks of real companies that provide real services.
    • by MasseKid ( 1294554 ) on Friday June 08, 2018 @12:22PM (#56750832)
      While I agree with most of your statement, cryptocurrencies do provide a real service. That service is a non-centralized bank transaction. The real value of this non-centralized bank transaction is where the speculation comes into play. That all being said, I don't think see such a network as being sustainable as the cost of transactions is exponential over time.
      • by Anonymous Coward

        And the non-centralized feature is also one of the biggest drawbacks.

        What happens when someone accesses your wallet and steals your currency? Who can reverse the transactions and get your money back?

        What happens when you lose access to your account? Who can verify your identity and restore access?

        Like any anarchist ideal, it only works if everyone doesn't have any ill intent. Once you have ill intent, you need some kind of enforcement capable of setting things right. Something that can govern, if even just

        • by fred911 ( 83970 )

          'And the non-centralized feature is also one of the biggest drawbacks.'
          Dependent upon your viewpoint. Decentralization relies upon verification and trust of all nodes. The hive mentality verifies the trust.

          "What happens when someone accesses your wallet and steals your currency?"
          The same thing that happens when you loose fiat currency.

          "Who can reverse the transactions and get your money back?"
          See above. Even if the transfer was adjudicated as fraudulent the probability of receiving compensation fr

        • Goodness knows why I'm replying to an AC, but the inability to reverse transactions is a feature! People get scammed all the time by customers reversing credit card charges once the transaction is complete. You can go ask Steve Wozniak about it.

          None of the items you mentioned are really drawbacks. Protecting access to private keys is not that difficult if you're competent with computer security.

          you need some kind of enforcement capable of setting things right. Something that can govern, if even just a little bit.

          Cryptocurrencies are clearly not for you! If you need a babysitter you can use the traditional money system.

      • by Anonymous Coward

        While I agree with most of your statement, cryptocurrencies do provide a real service. That service is a non-centralized bank transaction. The real value of this non-centralized bank transaction is where the speculation comes into play. That all being said, I don't think see such a network as being sustainable as the cost of transactions is exponential over time.

        Do you really think that it is all good with non-centralized transaction? There are plenty of ways to exploit it when nobody is controlling or at least some control. New problems will arise and the currency itself will eventually fail.

        Decentralized currency is an "ideal" only and it is extreme. Humans like to do things their own way. For example, if you give a problem and a computer to 1000 people and let each solve the problem on the computer their own way, what do you think would happen? That's why extrem

    • by Gravis Zero ( 934156 ) on Friday June 08, 2018 @12:23PM (#56750850)

      People are prostituting them selves for chucky cheese tokens

      Oh come on! Who among us hasn't given BJs and handies in the ally behind Chucky Cheese for tokens? You do realize they have pizza and video games, right? ;)

    • The entirety of the Netherlands is growing tulips instead of food.

      Flevoland is growing tulips. Actually not true. Noordoostpolder is growing tulips. That's a couple of hundred of sq km worth. The rest of the country on the other hand is not only growing enough food for itself but is also providing food for a fair chunk of the EU as one of the biggest food exporters in the world.

      I hate cryptocurrencies as much as the next guy, but it helps your argument if you don't start the first sentence with senseless hyperbole.

  • OK it's a bug if you want "no single person" to control a blockchain, but it's a feature for "captive" blockchains like bank- or governmetn-backed digital tokens.

    If the US Federal Reserve wants to issue tokens with a fixed value of, say, 1 United States Dollar, they will want to "control" the blockchain, perhaps only allowing banks and other licensed entities to process transactions.

    The same goes for a business that uses transferable tokens as gift certificates - they or their agent will want to control the

    • by Aaden42 ( 198257 )
      Something nobody trying to sell "private blockchain" has ever adequately explained to me: If you have an entity or entities that you want to have full restricted control over the blockchain, why use blockchain? Have them store it in their nice plain old database, publish it on the web if they want, whatever. I can't see any way that burning a ton of coal to solve hashes improves any part of that scenario.
  • by Anonymous Coward

    So there is this old adage. Goes something like this.
    If you build it they will work around it.

    Maybe that is just my cynical take on things which has been learned over years and years of systems development and implementations.

    Bottom line.
    Never say never.
    If it is, someone will find a way to benefit from it and/or work around it, legal or not.

    On that note. I like my finances to be on paper.
    I like my money to have a trail.
    I like that my money is insured and backed.
    I don't worry that my money is going to disa

  • by Anonymous Coward

    Now we can go back to the old ways of buying drugs: Cash and sex.

  • If I were into that kind of thing, I'd use a botnet to do it.

  • ... only for PoW alt-coins which are barely used. Bitcoin and Ethereum are safe. This kind of attack will be impossible against these two currencies unless you have hundreds of millions of dollars to spare.

    PoS coins are not affected but they are vulnerable to another type of attack (network cloning) - no one has carried such an attack yet though.

    • by Balial ( 39889 )

      Given that Ethereum has had a centralized hard-fork and bitcoin has had a mining pool over 50% control, your faith in those coins seems very misplaced...

      https://www.coindesk.com/ether... [coindesk.com]

      https://arstechnica.com/inform... [arstechnica.com]

      • bitcoin has had a mining pool over 50% control

        It doesn't matter how big the pool is. The pool doesn't own all that hardware; they're just managing it for others. If they tried to abuse their position to execute a 51% attack the miners would either shut down their hardware or jump ship to another pool and the misbehaving pool would no longer control 50% of the hash rate.

        As for the smaller altcoins, there is a well-known defense against this issue: merge-mining. This leverages Bitcoin's superior proof-of-work network to provide additional verification fo

  • is https://www.crypto51.app/ [crypto51.app] saying that $630K would make me solely authoritative for the bitcoin BC for a couple hours or so ?

    • For exactly one hour. Also I suspect its theoretical - while this would be cost of computing power it would need to be actually available for rent. If you go down the list you find more practical targets eg Bytecoin with market cap of over 1B$ and cost of attack under 600$/h

    • Seems to be.

      I think there are mafia organizations that a sophisticated enough to spend a couple million to make an attack, pump up the panic that will shock the price of the coin, gain a little lucre on the side from double spending, and scoop up tens of millions from selling the coin short before the attack.

  • "Blockchain's"

    Because there's only one blockchain?

    What is this, Highlander?

    Or just clickbait journalism?

  • "Attack vector?" (Score:5, Interesting)

    by DRJlaw ( 946416 ) on Friday June 08, 2018 @12:16PM (#56750800)

    In each case, attackers have been able to amass enough computing power to compromise these smaller networks, rearrange their transactions and abscond with millions of dollars in an effort that's perhaps the crypto equivalent of a bank heist. More surprising, though, may be that so-called 51% attacks are a well-known and dangerous cryptocurrency attack vector.

    That's not an attack vector, that's using the rules to your advantage. The designers expressly adopted a design rule that says that "51% of the current computing power dictates reality." The designer may not have intended for any one group to amass 51% of the current computing power, but intending that nothing "bad" will ever happen is not sufficient in engineering, contracts, law, or any other aspect of human endeavor that has evolved to survive contact with the real world.

    A bunch of people who want to make money using blockchain technology are become quite ticked off that a group of other people who want to make money using blockchain technology are using that blockchain technology as expressly designed to take their money.

    Thankfully the article seems to be focused on improving the designs rather than demands that governments intervene in these "government not welcome" currency projects.

    • The problem isn't about rules. The rules were originally designed that for disagreements so that transactions 51% of the group decides a dispute. Where this becomes an attack vector is it is possible for a large enough group to create bogus transactions and get them accepted into the chain. After a time, the transactions become permanent and cannot be changed.
      • by DRJlaw ( 946416 )

        The problem isn't about rules. The rules were originally designed that for disagreements so that transactions 51% of the group decides a dispute. Where this becomes an attack vector is it is possible for a large enough group to create bogus transactions and get them accepted into the chain. After a time, the transactions become permanent and cannot be changed.

        I love how you believe that "disagreements" and "bogus transactions" are in any way different, especially in any technical way regarding recording int

        • I love how you believe that "disagreements" and "bogus transactions" are in any way different, especially in any technical way regarding recording into the blockchain.

          They are different in the same technical sense that a buffer overflow is not a privilege escalation. One is a flaw that can occur in programming and one is an attack meant to undermine a system. The intent and use are different. Disagreements in Bitcoin can occur when two competing miners solve a block at nearly the same time and how to resolve who should be awarded. A 51% attack means that some entity can effectively control the whole network and all transactions. Do you see the difference now?

          • by DRJlaw ( 946416 )

            One is a flaw that can occur in programming and one is an attack meant to undermine a system.... Do you see the difference now?

            Yes. One is a flaw that can occur in programming and one is a use of an intentional feature of the design of the programming.

            Of course you've now shifted focus to the programming and not the transactions. The transactions exercising the intentional feature of the design of the programming are not in any way different, especially from a technical perspective. One merely has a "di

            • Yes. One is a flaw that can occur in programming and one is a use of an intentional feature of the design of the programming.

              No, one is a flaw and one is the exploitation of a flaw. A privilege escalation [wikipedia.org] is not an "intentional use" of feature by definition. Please read up on what it is.

              Of course you've now shifted focus to the programming and not the transactions. The transactions exercising the intentional feature of the design of the programming are not in any way different, especially from a technical perspective. One merely has a "disagreement" as to whether a block was solved by a miner, or whether a coin has actually been spent. The fact that you consider mining the block or wanting the transaction spending the coin to complete to be a prerequisite is irrelevant to the system and design.

              Of course you missed the point entirely. The difference as I said are by definition. The difference is intent and use. Please read above. The difference A programmer doesn't intend to have buffer overflows in his program but a hacker can take advantage of them. A 51% attack is an entity trying to take control of the network where a disagreement i

    • because the baseline for crypto currencies is and remains drugs and money laundering. What I'm wondering is if governments will ever crack down on that. If they do expect the value to plummet. Currency is worthless if it can't be exchanged for goods/services, and there's almost nobody taking even bitcoin for anything of actual value, let alone all the other currencies out there.

      If I sound harsh it's because I'm a little ticked that a buddy of mine spend a bunch of real money on one of those "Proof of St
  • Should say "crypto currency's use of blockchain"
  • by Comrade Ogilvy ( 1719488 ) on Friday June 08, 2018 @12:20PM (#56750814)

    The main potential gains from a 51% attack are (1) trashing of a blockchain, primarily reducing its credibility, or (2) double (triple?) spending.

    Basic theory assumes that the financial advantage of playing nice and mining is greater than can be achieved from the above.

    I would like to see the math on that. Because, in theory, I could get a loan of a bunch coin, rent enough computing power for a 51% attack with that coin, short the coin, double (triple?) spend the coin, and then buy the coin I need at a reduced price after the market responds to the shock. Bitcoin itself may be too big to attack in this manner at this moment in time, but...

    I cannot speak to all blockchains, but the basic theory makes assumptions that hardware is a sticky and expensive thing, so the weight of many servers already dedicated to a blockchain will be too high a barrier to scale.

    The new world may utterly crush those assumptions because: (1) there is a large and growing ecosystem of efficient blockchain mining machines that will happily and quickly work on another blockchain for the right fee, (2) that ecosystem is rapidly growing and well beyond the scope of any one blockchain, (3) the ability to simply rent one thousand servers for an hour is getting easier and easier, and cheaper and cheaper.

    • I cannot speak to all blockchains, but the basic theory makes assumptions that hardware is a sticky and expensive thing, so the weight of many servers already dedicated to a blockchain will be too high a barrier to scale.

      What hardware and where? Do you want to gain over 51% of power over Bitcoin? If it were available you could rent that kind of hasing power for $700k for one hour. And one hour is all you'll need to make off with more money than that.

      Fortunately Bitcoin is too big to make that kind of computational power available for rent. Most companies with ASICs massively parallel processors don't offer those kinds of resources.

      On the other hand Zencash was recently 51%ed and the attackers made off with $550000. If they

  • This is more akin to a run on a currency than a bank heist. George Soros did the same to the GBP and the GBP is one of the biggest currencies in the world. Any small country's currency is vulnerable to a similar attack. They protect against it by holding USD reserves. This gives the US way too much control as any country the US wants to f*ck with US can put sanctions so that they cant use US banks and without using US banks its very difficult to hold USD reserves (Iran and North Korea come to mind as being

    • I am a little confused. When one or more cryptocurrencies are under attack, what does "withdraw Bitcoins mean exactly"? You can sell Bitcoins immediately for USD easily enough on some exchange, I suppose. But unlike normal currencies where enormous banks/countries have adequate trust to make monster loans in an emergency based on politics and handshakes in the proverbial smoke-filled backroom, a cryptocurrency may not be able to make any transactions. In theory, that could apply to Bitcoin, too, BTW.

      • by ghoul ( 157158 )

        Well say Verge is about to get to 51% attack and you realize its happening you can go to any online exchange and exchange Verge for Bitcoin. Yes an attack could happen on bitcoin but then a Soros type attack could happen on the USD too. The chances are small. The larger the scale of the currency the more difficult it is to attack.

      • by xvan ( 2935999 )
        Bitcoin price is unregulated. There is no as you say, Big Bank behind it. Exchanges are also unregulated as of today. In case of stupidly high volatility, they could just block shut down.

        I don't think it's possible a 51% scam is possible. Imagine a 51% attack. It's really costly. You have all your investment on ASIC boards, plus all the infrastructure installation (power and bandwidth and storage ). You use your mining power to modify transactions. Immediately after the price of bitcoin plumbs to 0. Real
        • It is plausible that an attack could be made by renting cpus for a couple hours for a few million bucks. Don't you think someone could scoop up 10X that by shorting a coin?

          It all comes down to the numbers. The ability to rent large amounts of cpus changes the game. Whether this is actually practical is not known, but it seems within the realm of plausible.

          • by xvan ( 2935999 )

            It is plausible that an attack could be made by renting cpus for a couple hours for a few million bucks

            It isn't plausible. Bitcoin mining leaders do it by dedicated hardware. Assuming your plan is renting general purpose GPUs on a computing cluster

            Maximum Bitcoin Total Bitcoin Hashrate is 43EH/s https://blockchain.info/es/cha... [blockchain.info] (E stands for Exa = 10^18) For a 51% attack, starting from 0, you'd need to add another 43EH/s to the pool. The Nvidia Tesla S2070 has a hash rate of 749.23

            You'd need to rent 57 Gigas of GPUs plus all the infrastructure to manage that. For context the third largest superco

  • Regular on shitcoins perhaps which only attract the FOMOs and the pump 'n' dumpers.
  • so-called 51% attacks are a well-known and dangerous cryptocurrency attack vector.

    It is a an attack vector, and it threatens far more than cryptocurrencies... What if 51% of voters decide, for example, that a tiny minority of the population ought to be enslaved again? Or that an even tinier minority have "too much" money [salon.com]?

  • This is known from day 1. It is the foundation of collective validation of each others transactions.

    In related news, "Battering Rams are a known attack vectors for doors". yeah. sure.

  • All the splinter chains are vulnerable to Beowulf-cluster alliance attacks.

    Unless you've got 51% of all available blockchain compute over all blockchains held by honest parties, your blockchain is at risk if all the hostile compute coalesces for a quick, selective heist (before going back to its sundry regular programming).

    Even worse: all available blockchain compute includes Amazon's instant army (and any other advanced GPU cloud service), though perhaps the ASIC-advantage presently renders this moot (I do

  • This is why we don't need 600+ altcoins and never did. Blockchains require large groups. These currencies don't have them. Stop inventing new ones thinking you'll get rich, people!
  • Future forks of cryptos may require geographic diversification of mining power using a non-spoofable, terrestrial GPS alternative that supports public key cryptography. http://bit.ly/2xxnDds [bit.ly]

Technological progress has merely provided us with more efficient means for going backwards. -- Aldous Huxley

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