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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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What can an attacker with 51% of hash power do?

Suppose organization X has 51% of the hash power for a period of 1 week. In this week, what exactly can and can't X do?
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How much would it cost to execute a 51% attack?

I know that it's commonly said that they're not really in the realm of possibility right now, but how much would it really cost to execute a 51% attack on the network? And are there any organizations ...
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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 ...
johnsmiththelird's user avatar
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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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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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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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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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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 ...
Nick's user avatar
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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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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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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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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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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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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 ...
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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 ...
Computerish's user avatar
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7 answers
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Is performing a 51% attack / double spend on Bitcoin illegal?

Suppose I had an ultra large ASIC from the future, and could perform a double spend on the core Bitcoin network. At this point in Bitcoin's development, it is no longer a game - there's real money ...
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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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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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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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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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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 ...
David's user avatar
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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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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/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 ...
David's user avatar
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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 ...
Will's user avatar
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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 ...
Cedric Martin's user avatar
6 votes
3 answers
280 views

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) ...
Artem Kaznatcheev's user avatar
6 votes
2 answers
349 views

Is there any software available for testing of Bitcoin security?

I'm currently in the process of working on my thesis about Bitcoin security and I'm wondering if there's any software available for testing of Bitcoin security? For example, are there any programs ...
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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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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 ...
Abbas Gadhia's user avatar
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2 answers
974 views

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 ...
scolnick's user avatar
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2 answers
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How does the network protect itself against attacks where one miner with a lot of hashing power lies that it takes 10 minutes to create a block?

Assume some very "strong" miner that can produce a new block (find a correct nonce) on average every 3 minutes. Everything is fine as long as he sets the right timestamp (the one ...
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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 ...
Curious's user avatar
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Can the two biggest bitcoin mining pools lock out all others?

I just noticed that the two biggest bitcoin mining pools already have more than 52.5% of the hashing power (as of 11/12/23 Foundry USA had 27,7% and AntPool 24.88%) and am wondering about the ...
Dr. Hans-Peter Störr's user avatar
4 votes
3 answers
786 views

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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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 ...
René Nyffenegger's user avatar
4 votes
1 answer
368 views

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 ...
Werner Thumann's user avatar
4 votes
1 answer
371 views

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 ...
user15628's user avatar
4 votes
1 answer
238 views

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, ...
nnnnnn's user avatar
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4 votes
2 answers
739 views

How many consumer computers would it take to launch a 51% attack [closed]

What is the hash rate of a standard laptop using the default client and what is it for the whole of Bitcoin? I am interested in this, because I want to understand what it would take to get to 51% of ...
David's user avatar
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4 votes
1 answer
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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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Can a 'China' or similar actor with more than half of the hash power really destroy Bitcoin?

More of a general question as I've recently gotten into investing in cryptocurrencies. I really love the vision for the future this technology provides, the freedom, ease of use, lack of middlemen, ...
user avatar
4 votes
1 answer
902 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 ...
JacKeown's user avatar
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1 answer
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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 ...
user avatar
4 votes
3 answers
396 views

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 ...
user avatar
4 votes
1 answer
295 views

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 ...
cryptonaut's user avatar
3 votes
4 answers
914 views

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 ...
Rhonda's user avatar
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3 answers
131 views

Don't miners control who is allowed to make transactions?

Simple question really, considering theres a very small group of miners controlling the chain ATM. Whats to stop them from being forced by the goverment to disallow certain transactions or just mining ...
user2741831's user avatar
3 votes
3 answers
782 views

How exactly are Bitcoin's consensus rules enforced?

There are some rules called consensus rules, for example the block generation amount. And it is said that "a change to consensus rules is a hard-fork". But how exactly are the consensus ...
Dmitry Andrievsky's user avatar
3 votes
1 answer
778 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 ...
Tail of Godzilla's user avatar