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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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51% attack - apparently very easy? refering to CZ's “rollback btc chain” - How to make sure such corruptible scenario can never happen so easily?

I was shocked to see binance CZ comment to literally "roll back" the bitcoin chain by just "calling" in some favors from "friendly" Asian miners . This ONE person could effectively do it??? I mean ...
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If there are 20 nodes in network and all are receiving transaction and after 10 min

Question 1) If there are 20 nodes in network and all are receiving transaction and after 10 min all will pick transaction from their transaction pool and start creating block, now will all nodes will ...
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Is 10K full nodes enough to bitcoin to avoid 51% attack?

As I know bitcoin has about 10K full nodes. And the question is in my mind is that: This number is not huge! If someone has 6K servers, Can control the bitcoin via 51% attack? I was thinking if ...
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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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Majority attack against a new blockchain with few miners?

My friend wants to create a new blockchain to verify a type of transaction (details unimportant). His computer would probably be the only one doing mining / verifying the transactions, at least for ...
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How to do a 51% attack on my own altcoin [closed]

recently I have been curious about 51% attacks so I created a fork of litecoin and want to do a 51% attack on the coin but don't know how to. please can you tell me how to do it. Thanks,
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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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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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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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51 views

Is a 51% attack on bitcoin likely?

Given that the majority of bitcoin processing is done in China (source: https://bitcoinmagazine.com/articles/report-links-74-bitcoin-mining-china-sees-threat-network/), is it possible for a single ...
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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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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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Other people mining my coin without my permission, how to avoid this?

I have created an altcoin and i wanted to solo mine all coins myself. I disabled generate function in wallet, hidden the source code as private in github. I run one main node and i mine in my laptop. ...
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1answer
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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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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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Why do we call it a 51% attack instead of a 50% attack?

From the Bitcoin paper: p = probability an honest node finds the next block q = probability the attacker finds the next block qz = probability the attacker will ever catch up from z blocks behind qz ...
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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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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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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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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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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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Why does Bitcoin no longer have checkpoints?

I've read that checkpoints in Bitcoin were removed because they were not preventing any meaningful attack. Why should a regular checkpoint not prevent majority attacks? For instance, if a checkpoint ...
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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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Why has BCH not received a 51% attack yet?

BCH right now has around 10% of BTC total hashrate. There are multiple pools that control 10%+ of the total BTC hashrate why haven't any of those just allocated a few hours of hashrate to do a 51% ...
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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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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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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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Do multiple miners contribute to mining the same block even if they are not in the same pool

Assuming that this is reliable, according to an article on investopedia on the 51 percent attack: 51% attack refers to an attack on a blockchain – usually bitcoin's, for which such an attack is ...
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Is it more dangerous when 51% attack happens than just having a pool with >50% hashrate?

Many people told me that, if a mining pool performs a 51% attack, the price of the coin will drop. But I disagree. There are pools with >50% hash power already for a long time. Flypool is an example....
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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 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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POW based blockchains systems Majority Attack

TL;DR: With only 30% of network power a Majority Attack is possible and profitable. Am I missing anything? Generally speaking, blockchains based on Proof-of-Work authentications are using amount of ...
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51% attack and rewriting to the latest checkpoint

This is not a question about the consequence of a 51% on the price nor as to the motivation of the attacker. Let say we don't care that it's not realistic and we don't care that the attacker wouldn't ...
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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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59 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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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 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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1answer
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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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1answer
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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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1answer
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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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1answer
459 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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2answers
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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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1answer
321 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?
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887 views

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 ...