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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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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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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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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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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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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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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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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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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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Can a 51% attack be detected and dealt with?

If someone got 51% hash power and started rewriting the blockchain from scratch (building a longer chain with a completely different history), could this be detected? Could "the honest users" revert ...
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What can xxxCoin do to stop the impending 51% attack?

Within the coming weeks both Namecoin and SolidCoin have been threatened with the same attack. What can be done by the users, pool operators and developers of these forks to either; A. Minimise ...
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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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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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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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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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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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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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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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Is possible to control the network? [duplicate]

Can anyone with enough computing power, take over the network ? This is following from a previous comment where I was asking : ... how can that be possible (to control the network) if mining tend ...
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Could miners create a cartel to raise transaction fees?

Could miners with enough mining powers (say >95% of all blocks) form a cartel where they demand absurdly high transaction fees? Of course, I still could could hope for a miner not in that cartel to ...
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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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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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1answer
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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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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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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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Is the minimum amount of money required to purchase >50% hash power equal to max worth of all existing bitcoins?

20 BFL Bitforce Mini Rigs (each, $30k) will give about 30THash/Sec hash power for $600k. That's way above 60% of hash power of then total 51THash/Sec. 10.694M total Bitcoin * $18.5 current mtgox best ...
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Are big miners a threat for Bitcoin?

According to this graph, the biggest miner is so big that combined with two of the three runners-up they would have more than 50% of the hashing power. Is that to be considered a threat to the ...
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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 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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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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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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What can be done about the no-transaction block relayer (currently 71.123.170.150)?

An unknown major solo miner (currently IP 71.123.170.150), most likely a botnet, is relaying blocks with zero transactions. Two weeks ago this miner constituted ~15% of the network, now it constitutes ...
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What is/Is there the relation between the value of a bitcoin and the prices of video cards?

A significant number of Video Cards (significant investment) are required to reduce the possibility of 51% attacks. What would happen to the price of a Bitcoin if the prices of Video Cards suddenly ...
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Can someone with 51% computing power earn more than he deserves?

See also What can an attacker with 51% of hash power do? This may have been discussed elsewhere, but I'm not sure what the answer is - if someone owns 51% of the hash power, can't he just ignore the ...
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Do miners have both the incentive and ability to keep the reward at 50BTC?

There has been some concern about the fact that transaction fees (in their current form) are not an adequate replacement for the current 50BTC block reward. Gavin has said as much, as have others. ...
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Are there any attacks with a plurality of computing power?

There has been some discussion about possible attacks if one has the majority (over 50%) of the computing power of the bitcoin network. What happens if an attacker (or coordinated group of attackers) ...
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String-along, is this possible and is it an attack?

I haven't seen this discussed before, if it has been please provide a link. If I find a block while mining but then discover that another miner broadcast a block mere moments ago, I could begin ...
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Could the EC2 infrastructure be used to efficiently launch a 51% attack?

This excellent answer from Serith states that one would need 31150 ATI 5870 graphics cards to launch a 51% attack. Amazon EC2 offers computers for rent for 2.10$ per hour. These instances have 2 x ...
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Can someone with an unlimited amount of money compromize the network?

I was reading this interesting discussion in the comments section on ZH where this guy was talking about how a single entity (think corrupt government and banksters) can throw money and processing ...
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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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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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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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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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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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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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Why did BitcoinEXpress plan a 51% attack on Namecoin?

I don't understand this post. What is "ArtForz modified exploit"? What does "Gavin's patch will not work for the exchanges" mean? Any more important details I'm missing?
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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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DDoS on big mining pools: a quick way to 51%?

Slush's Pool, the second biggest mining pool around, is currently down, allegedly due to a DDoS attack: News 16.04.2013 Pool is under DDoS attack. I'm working on recovering the service back to ...
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Why would you need to “catch up” in the 51% attack?

There is a lot of information on the 51% attack where an attacker is able to branch the chain and "catch up" and build a new branch that is longer than the old branch. Other than requiring more than ...
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Would any of the current botnets be able to launch and sustain a 51% attack?

The "owners" of botnets probably runs them as businesses, meaning that they will always seek profit-optimization. Do you believe that it is a matter of time before they will seek to launch and sustain ...
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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 ...