Questions tagged [majority-attack]

A majority attack, or 51% attack, is an attempt at solo-mining a longer chain to outpace the main chain.

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What is the worst an attacker could do with full control over the blockchain?

Let's assume somebody gains control over 100% of the hashing power and is now free to mine and control as many new blocks as he wants. What would happen? The attacker still could not include any fake ...
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What are the implications of a huge amount of unused hash power?

A not unthinkable scenario is that the Bitcoin price decreases to, say, 10-20% of today's value. This would make mining less profitable, and the difficulty should adapt accordingly. This should lead ...
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Why don't the miners just take profit from our coins and make the coin worthless?

You own a very valuable thing and you want to go to holiday without it, but there is nobody who you trust and who can look after the thing. So you take somebody unknown to guard it. You pay him a fee ...
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How much money would it take to bribe the majority of miners to attack the system?

I think this question is just a re-formulation of the 51% attack, but it has me thinking: miners are monetarily incentivized to not perform a 51% attack, but there must be some amount of money will ...
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Egoistic miners combined with large transactions destroy PoW?

EDIT There is a clearer description of some parts of the problem in the link questions. If there is a transaction value much higher than the payment for mining 10 new blocks, how can you trust this ...
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51% attack clarification

Im just reading a book on the basics of blockchain and I encountered a confusion regarding the 51% attack. If I'm right, it says that an attacker holding 51% or more of the network's computing power ...
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Attack vectors for difficulty retargeting with BCH and BTC?

Since the existence of BCH, miners can now switch chains to mine on. Assuming they mine greedily based on price and difficulty. Can the following attack happen and how could it be mitigated: Assuming ...
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Was the 51% attack a real threat in the early days of bitcoin existence?

The hypothesis of 51% attack is based on a malicious entity is able to control more than 50% hashrate of all mining nodes. It's understandable that there's huge amount of mining power existing ...
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How exactly bitcoin consensus rules are forced?

There are some rules, called consensus rules. For example, block generation fee amount. And it is said that "change to consensus rules is hard-fork". But how exactly the consensus rules are forced? ...
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Understanding reinvestment in a miner growth scenario

I got the following question which I can't figure out: Alice, Bob, Carol, David and Eve are the five major bitcoin miners. They have each invested a million dollars in specialized equipment for ...
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Why wouldn't miners change the protocol? (e.g. change difficulty)

How about a scenario where a few miners change their protocols by setting difficulty to something easy. Let's take it to the extreme and say they are able to accept any block. They would keep ...
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What concerns arise from the heavy miner concentration in China? [duplicate]

As per an Business Insider article last year, approximately 73% of the hash power comes from China. Over 50% just by the top 3. If coordinated, they could cause havoc. Is that a concern to anyone?
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IOTA Security with Tangle

I don't know if this is the best place to ask this, but I've been reading about an interesting cryptocurrency called IOTA which doesn't use a blockchain exactly but instead uses a directed acyclic ...
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What's to stop someone from making a ton of mining nodes as an attack method?

My understanding is that if two miners make a block by completing a hash at the same time, it is then up to the miners to decide which is going to be 'accepted' by vote of which block reaches 51% of ...
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Does the software to conduct a 51% attack exist?

I know that it would cost hundreds of millions of dollars to do a 51% attack on Bitcoin, but if somebody did that, bought the hardware, etc could Bitcoin Core or any other software be easily ...
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How to extract maximum value from a 51% attack

If an attacker were to gain 51% of the network, they can essentially forge arbitrary transactions double spend. But that would quickly lead to a completely loss of trust in bitcoin. In fact, that ...
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Minority Attack on Bitcoins

I read the first paper which described the bitcoins. Most of it is clear except for one thing. I tried to find solutions online but couldn't find it. I am completely aware of the implications of a ...
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What is “If ghash.io hits 51% people would just leave them?” referring to?

I am watching video that explains original Bitcoin whitepaper by Satoshi Nakomoto. I totally understand that as long as 51% of the CPU power is legitimate then using bitcoins is safe. But then the ...
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Incentive and 51% attack

White paper: "The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to ...
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What incentive is there for a miner to not cancel his own 'real' txs

It is said that a Bitcoin miner attacker with enough CPU power to outrun the entire network is better off mining honest bitcoins - which is not correct since by creating a false block chain the ...
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Majority attack no drawbacks (unlike bitcoin wiki suggests)

In the bitcoin wiki article on Majority attack (https://en.bitcoin.it/wiki/Majority_attack) it says: "No amount of confirmations can prevent this attack; however, waiting for confirmations does ...
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Can a malicious majority miner rewrite history?

Is it the case that a malicious miner with the majority of hash power (say, 99%) can perform a double-spending attack by rewriting history? If so, I can't understand how. If not, under what ...
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How much would it cost to do a 51% attack

how much would it cost to carry out an 51%-Attack? If there is a place service in the web that you can rent ASIC's than i would rather hear what renting this would cost. If not then buying the asics ...
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Do we need to maintain the ability to do a reorg over 100 blocks?

The protocol requires that freshly generated coins wait 100 blocks before they can be spent in order to avoid polluting bitcoin addresses with bitcoins that are "uncreated" by a reorg that invalidates ...
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When an attacker publishes a longer chain, does Bitcoin Core emit a warning?

I tried answering a question about a majority-attacker's power to change the blockchain yesterday. There is one thing I haven't been able to get a clear picture on, yet: When a previously unknown ...
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Can an attacker with 51% of hash power change old blocks?

I read what an attacker with 51% of hash power can do in here and here. However, I want to know whether an attacker with 51% of hash power can change old blocks? For example, assume the attacker has ...
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Where is coinbase transaction after a hacker successfully performs >50% attack?

Here is the scenario: Honest nodes build one block from Block_1. Hacker nodes privately build four blocks from Block_1 and broadcast these malicious blocks. Now, where is the honest node's ...
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Why does an adversary have to control 50% of the computing power to double spend?

If transactions in a block are valid, in order to add that block in the block chain, a proof of work needs to be found. I have read the bitcoin paper by Satoshi. If the difficulty of the proof of ...
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Why doesn't bitcoin place additional constraints on competing block chain forks, other than length of chain? (e.g., time and confirmation count)

In Bitcoin's proof-of-work system, consensus on which chain of blocks should be considered the "true" block chain is based only(?) on which chain is longer. Accordingly, to quote a nicely written ...
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Profit possibility for colluding with 51% attacker

The Bitcoin Wiki states "A profit-seeking person will always gain more by just following the rules, and even someone trying to destroy the system will probably find other attacks more attractive." I'...
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Would it be possible to overtake the network by running a secluded mining operation for many years?

I have a scenario. Let's say I start my own Bitcoin mining on a secluded network. I leave this to mine for many years or even pass it down to future generations. To the very point that my chain is ...
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How does CryptoNote prevent a 51% attack and double-spending?

How does CryptoNote prevent a 51% attack and double-spending? I’m interested to know what is the mechanism that protects CryptoNote coins from 51% and double-spending attacks.
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Does hardware specialization provide security against 51% attack via on-demand computing?

I've heard it argued that when a mining algorithm is prone to hardware specialization, the centralization that introduces (e.g. one factory producing 25% of all ASICs) is a security risk. I'm ...
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Supermajority to prevent 51% attack?

I would think that amending the bitcoin protocol to require a supermajority, say 60% or 75%, to verify proof of work help reduce the risk of a 51% attack. If this is so, what are the major obstacles ...
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Can I detect a 51% attack as a developer

I am a developer building an application that accepts payments in cryptocurrencies. Is it possible, in the occurence of a 51% attack, to build a script that detect this, so we can suspend withdrawals ...
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How can we trust any crypto currency if the NSA could use 51% attacks? [duplicate]

My understanding of cryptocurrencies is that with the "51% attack" you can fake transactions and stop anybody from making any transactions. If any crypto currency actually threatens Government backed ...
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Is it possible for more than 21 million bitcoins to exist if 51% agree?

One of the commonly cited advantages of bitcoin is that there's guaranteed to be only 21 million bitcoins. However, my understanding is that the bitcoin protocol is patched by an opensource community,...
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Who would accept confirmations of invalid transactions in a 51% attack?

My understanding is that honest nodes work on the longest valid block chain. Suppose a dishonest node confirms an invalid transaction. If that node manages to continue producing confirmations at a ...
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Can a double spend attack be obfuscated by mimicking the transactions seen before the fork?

An attacker controls the majority of the hashing power and wants to double spend without arousing suspicion. If they mirror the public chain's activity while generating the private fork and the fork ...
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Does Bitcoin's SHA256 proof make a 51% attack more likely?

Ethereum's description says that Bitcoin's mining algorithm requires only a simple SHA256 computation, which caused the creation of specialised ASICs, which centralizes mining in the hands of a few ...
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Can the bitcoin network hashrate be used for a 51% attack on other coins?

Please correct me if I am wrong. The difficulty constantly changes according to the current hash rate. It changes to ensure that a block is mined every 10 minutes. If the hash rate was 1000 TH/s and ...
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What are the pros and cons of P2P mining pools?

I've heard P2P mining pools are the answer to the current threat of mining pools controlling 51% of Bitcoin's hashing power. Is this true or not true? Does anyone have a supporting or critical ...
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I don't understand the “51% attack” problem. Why does a mining pool have power with a 51% share?

What gives a mining pool power to maliciously dominate the system if they're mining over the majority of the coins? Profits are disseminated to miners individually. I really don't understand how this ...
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Has anyone ever gained control of the blockchain?

I've heard discussion that if you have 51% of the network's hash power, you can effectively accept or reject any changes to the blockchain (and therefore create undeserved gain for yourself). Has ...
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Does a 51% attack depend upon difficulty?

Does increasing difficulty also serve to decrease the probability of a 51% attack? It seems that since difficulty is the same for all, this is not the case. Is that correct? If difficulty were ...
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Is a 51% attack really expensive?

In order to perform a 51% attack someone has to concentrate huge amounts of computing power. Obviously this would be very expensive. But in return the attacker obtains the block reward and mining fees ...
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Does Proof of Stake Lead to a Positive Feedback Loop?

(I may have horribly misunderstood PoS, so be gentle!) Reading about PoS, the general idea seems to be that each miner has a "hit rate" proportional to their coins / total coins in the system. Now, ...
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What are “automatic coin choice pools”?

Referenced in this thread about a 51% attack on feathercoin. This would have been a hell of a lot worse without automatic coin choice pools. They routed a ton of hashpower at FTC. This broke the ...
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Is it a 51% attack or a >50% attack?

Is it 51% attack or 50.0000...1% attack? Bitcoin is getting to a point where 1% is a lot of hashing power... My understanding is >50% due to the nature of the protocol.
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What is the Ripple equivalent of the “51% attack?”

In Bitcoin, if a participant gains control of more than 50% of the hash power, they can execute a double-spending attack. The "attack" could come from within, say if the existing powerful miners ...