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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4answers
314 views

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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2answers
5k views

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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2answers
320 views

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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1answer
574 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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1answer
446 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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2answers
600 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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1answer
116 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 ...
6
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3answers
682 views

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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2answers
180 views

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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2answers
1k views

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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1answer
45 views

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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2answers
2k views

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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2answers
491 views

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 ...
8
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4answers
569 views

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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1answer
456 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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2answers
208 views

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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2answers
645 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 ...
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2answers
238 views

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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2answers
1k views

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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3answers
167 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 ...
3
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1answer
221 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 ...
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2answers
89 views

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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1answer
275 views

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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2answers
125 views

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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