Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [majority-attack]

A majority attack, or 51% attack, is an attempt at solo-mining a longer chain to outpace the main chain.

130
votes
8answers
47k views

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?
26
votes
5answers
2k views

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 ...
20
votes
4answers
3k views

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 ...
15
votes
3answers
4k views

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 ...
4
votes
3answers
349 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 ...
21
votes
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 ...
12
votes
3answers
2k views

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 ...
8
votes
3answers
998 views

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. ...
3
votes
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?
2
votes
1answer
511 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 ...
3
votes
1answer
246 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 ...
1
vote
1answer
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 ...
4
votes
2answers
639 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 ...
3
votes
1answer
2k views

I don't understand the “51% attack” problem. Why does a mining pool have power with a 51% share?

What gives a mining pool power to maliciously dominate the system if they're mining over the majority of the coins? Profits are disseminated to miners individually. I really don't understand how this ...
11
votes
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 ...
8
votes
4answers
563 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 ...
7
votes
5answers
373 views

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 ...
5
votes
2answers
1k views

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 ...
4
votes
1answer
646 views

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 ...
3
votes
1answer
207 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 ...
7
votes
7answers
2k views

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 ...
3
votes
1answer
123 views

When an attacker publishes a longer chain, does Bitcoin Core emit a warning?

I tried answering a question about a majority-attacker's power to change the blockchain yesterday. There is one thing I haven't been able to get a clear picture on, yet: When a previously unknown ...
2
votes
1answer
96 views

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 ...
1
vote
2answers
274 views

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 ...
1
vote
1answer
113 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 ...
0
votes
2answers
99 views

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 ...
-1
votes
1answer
37 views

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 ...