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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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Bitcoin is attacked by China miners by screwing with the network, what will Bitcoin do?

There was a report recently (https://arxiv.org/pdf/1810.02466.pdf) that stated that China controls 74% of the hashing power. They can choose to collude and attack the network by either doing a 51% ...
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Why is it more profitable for a node with more than 51% computation power to abide by the rules in the bitcoin network

The Bitcoin whitepaper states - "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 ...
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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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Developments to prevent 51% hack [duplicate]

How might Bitcoin be made impervious from attack by large monied interests that could atttack with a brute force majority hashrate hack?
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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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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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542 views

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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320 views

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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1answer
311 views

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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165 views

Is there a limit to how many blocks can be rolled back from a 51% attack?

I was wondering if we where to ever face a 51% attack is there some sort of limit as to when the longest chain doesn't matter? For example if I owned 51%+ of the network, mined 1000 blocks privately ...
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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 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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How long does it take to go from 51% hash power to 100% hash power?

Once an attacker has acquired 51% hash power, is it possible to quickly get to 100% hash power by simply refusing to build on blocks created by other mining nodes and therefore discouraging mining ...
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391 views

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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3answers
161 views

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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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 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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Why more confirmations would help in a 51% attack scentario?

After the 51% attack on Bitcoin Gold. The developers of the cryptocurrency recommended the exchanges to increase the confirmations. I don't understand why would increasing the confirmations help if ...
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598 views

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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115 views

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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1answer
440 views

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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115 views

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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double spend attack: Is this actually true for the more time progress the higher the probability of success for attacker

I'm new here. I have a question here. Some experts keep saying that this assumption isn't formally correct and I don't really understand why or why they might be wrong. In the double spend attack; ...
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On a low level, how are long chains kept secret and later broadcast during 51% attacks?

I've been reading about the vulnerabilities of PoW crypto, and there's a part of it that I don't understand. Suppose I wanted to stage a 51% attack on Bitcoin (not really feasible, but bear with me). ...
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227 views

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'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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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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How do I know that the majority of bitcoin miners are not XYZ government's facilities? [closed]

Even if "Satoshi Nakamoto" is/was actually a real person, how can I be sure that XYZ government (XYZ can be US, or China, or ...) does not have now (or will not have in the future) 51% of the hashing ...
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Given that you have the necessary computing power, how does a tampered blockchain get accepted by the network?

I read that you can only tamper with a blockchain if you have more than 50% of the computing power in the network. So say you have 51% of the computing power, then you can create a longer blockchain ...
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183 views

Forking Bitcoin how to prevent a 51% majority attack

Lets say I fork Bitcoin, to lets call it StackCoin. How do I prevent a 51% majority attack when miners are not in abundance? Would I have to setup a lot of miners to create the infrastructure of the ...
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120 views

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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93 views

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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415 views

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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52 views

How prevalent are coin attacks with botique altcoins?

I have deployed several altcoins using various PoW algorithms on my LAN for my buddies and I to mine/learn from. We ultimately want to go the distance of deploying an altcoin to the world, writing the ...
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127 views

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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74 views

Why can a 51% attacker not change the block reward?

It is said that in the case of an attacker having a sustained 51% power, the attack still cannot change the block reward. Why? My naive understanding is that, since consensus is controlled by the ...
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Do you really need more than 50% mining power in order to attack Bitcoin blockchain?

My question is about concept, so code is not related, however, do you really need 51% of the mining power in order to attack/replace the real bitcoin Blockchain? For example, a blockchain has a ...
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248 views

What do we mean by honest nodes?

In his recent paper, Vitalik often mentions the term "honest nodes". What do we mean by that exactly?
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Robustness of bitcoin

I am wondering about the consequences of a potential 51% CPU attack on the bitcoin blockchain. Imagine that a state invests enough computational power to rewrite from scratch an entire blockchain, ...
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214 views

51% attack on New coins

I have experienced 51% attack after launching a new altcoin last month. While i mined only 100 blocks using coin-cli generate 1, i noticed somebody already mined 2000 blocks within minutes attacking ...
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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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51% attack + ignore blocks not mined by yourself [duplicate]

If you own 51% of the mining power and decide to ignore all blocks not mined by yourself. You would eventually end up having the longest chain, and would eat up the 49% of block-reward you werent ...
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1answer
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Are smalltime block chains susceptible to brute force liars?

My understanding is that the integrity of the bitcoin block chain is dependent on the consensus of the masses - that no single actor can write entries at will unless they. controlled over 50% of the ...
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Are Bitcoin and Ethereum really de-centralized? Or is federated a better term?

By looking at the bitcoin and ethereum mining pool hashrate distribution I feel that only 5-10 relevant full nodes exist. So it's more like a federated system among those. Am I seeing something wrong ...
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What happens if an ISP isolates a portion of nodes?

I came to believe that an ISP can easily detect full nodes, BTC connections and isolate them from reaching any other nodes. When and if an ISP decided to do so, could they easily perform a 51% attack ...
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What is the actual threat of a majority attack on the Bitcoin blockchain? [duplicate]

As far as I understand, an attacker (in the role of a malicious miner) controlling a large portion of the current hash power could replace previously accepted blocks with alternatives. But, what does ...
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60 views

What prevents a majority attack from undoing transactions of others?

From the Wiki: If the attacker has the majority of computer power, "the attacker can't reverse other people's transactions without their cooperation." I don't quite understand why this must be the ...
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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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463 views

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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1answer
322 views

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?