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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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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Is possible to destroy the Bitcoin for just $500K? (51% attack)

Everytime I read about the 51% attack the answer was something like: is really expensive to get 51% of power on BTC and nobody will invest so much so to destroy the bitcoin. But I found this site ...
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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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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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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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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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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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Why is a 51% attack guaranteed to outpace the rest of the network's miners? Doesn't 51% hashing power give only a slightly higher chance?

I thought hashing power is an expression of the probability of being the one to solve the cryptographic puzzle and placing a new block on the network. If that's true, owning 51% of the hashing power ...
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Why would more confirmations help in a 51% attack scenario?

After the 51% attack on Bitcoin Gold. The developers of the cryptocurrency recommended the exchanges to increase the confirmations. I don't understand why increasing the confirmations would help if ...
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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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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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Can attackers change transactions during a 51% attack?

If in a 51% attack transactions can be reversed, isn't it possible that the chain with more hash rate also changes transactions (for example if x sent 5 btc to y, they would change it to x sent 500 ...
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transactions and 51% attack?

I have a very basic understanding of how the bitcoin blockchain works and am trying to understand how manipulating transactions in a 51% attack works. I just watched a video which stated 51% attacks ...
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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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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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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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How does the bitcoin core protect against initial DNS seed changes?

While the bitcoin network is essentially P2P, one still needs to identify an initial node to connect to. I understand that a method for such initial connections is connecting to known DNS seeds, e.g ...
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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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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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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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What are the benefit of mining an empty block

Something peculiar just happened on the newly mined block number 655534, it contain only the coinbase transaction, nothing else. I have searched for a similar question but only found this one Why ...
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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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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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Why can't a 51% attack change past blocks on the blockchain?

I have read that it is not possible to reverse transactions already added to the blockchain but I do not understand why that is not possible in a 51% attack. If an attacker was to change the ...
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Reversing network hashpower

I'm reading this article by Vitalik Buterin on Problems in Cryptocurrency and don't quite understand what this means: Ideally, after some number of blocks (perhaps logarithmic in the total size of ...
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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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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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Noob question: Why is there not a limit of the number of blocks in a chain revision?

I have a noob idea and I want to understand where I'm going wrong :) Say nodes agreed on a block revision limit, say, 6. This would mean that if they see an incoming chain that is longer than the ...
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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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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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51% attack, miners, nodes or both

If 51% of the hashrate was controlled by bad actors mining invalid blocks, this would become the longest chain. Where do nodes come into the 51% attack? The canonical chain is the longest chain. Is ...
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Did Satoshi Nakamoto (in his blogs or the whitepaper) forecast that mining pools would exist?

Mining pools are common today where users pool their resources together and share profits accordingly. Such pools today can account for significant proportions of a network's hash power and they're ...
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How can Forks and Orphan Blocks be used to attack a Blockchain?

So I'm trying to learn about the security aspects of Blockchains and one of the papers I'm reading (https://arxiv.org/pdf/1904.03487.pdf) states that Forks and Orphaned Blocks can be used to attack a ...
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How does longest chain propagation take place in bitcoin?

Let's say the valid blockchain that Node A has is: B1->B2->B3 Now, I am gonna cheat since I have lots of computing power. What I do is I download the above blockchain that Node A has and start ...
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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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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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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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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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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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Attacker Changing Address to Receive Block Reward [duplicate]

A miner creates a block B which contains address α, on which he wants to receive his rewards. An attacker changes block B, such that instead of α it defines a new address α’, which is controlled by ...
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Why one miner can dig out many blocks continually in one moment?

I am new to bitcoin and blockchain, I browed the website just now. There is a question confusing me, I find that one miner dig out blocks many times even in one hour. For example, this miner dig out ...
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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 ...