<p>No. The 51% hack is considered one of the main ways a hacker could control the network. However, it is almost completely implausible because of the sheer amount of power that would be required to have 51%. For example, the total hash rate of the network is currently 6.09 Exahashes per second. So, if a hacker wanted to take control of the network, he would need to buy about 6.1 Exahashes per second of hash power. An antminer S9, for 3,000 dollars, gives you 14 terrahashes per second. Thus, the supposed hacker would need to buy 435,000 Antminer S9's which would cost 1.305 billion. That's not even considering the growth rate of the network and the sheer amount of space and energy required to host all of those Antminers.</p>

CC BY-SA 3.0
2017-07-12T17:18:11.253Z
No need by buy ASICs to do 51%-attack. Just create a mining pool with 5% bonus available for withdraw after a year of mining. :)
amaclin
CC BY-SA 3.0
2017-07-12T21:25:56.480Z
I believe the question was referring to number of *nodes* not mining power?
meshcollider
CC BY-SA 3.0
2017-07-12T22:36:12.027Z
I should have clarified it, yes. But the mining power is the number that actually matters I believe.
James P.
CC BY-SA 3.0
2017-07-12T23:58:51.480Z
Yes you are correct, but I will post another answer to clarify that for everyone
meshcollider
CC BY-SA 3.0
2017-07-12T17:06:09.383Z
2017-07-12T17:06:09.383Z
James P.
<p>In verifying transactions, it is not the <em>number</em> of nodes that an attacker owns, but the hashing power which matters. Having many bad nodes (Sybil attack) could affect the network in other ways such as not relaying all transactions, etc, but you can't trick an honest node into accepting a different blockchain without mining enough blocks for it to become the largest chain in the network, and that requires more than 51% of the hashing power to race against the rest of the network.</p>

CC BY-SA 3.0
2017-07-12T23:58:09.307Z
2017-07-12T23:58:09.307Z
meshcollider
<p>my question is simply What if a malicious owns more than half of the nodes in bitcoin network? she can simply fraud then. isn't there any algorithm to prevent someone from having more than half of nodes in bitcoin network?</p>

CC BY-SA 3.0
2017-07-12T14:54:02.883Z
maybe you mean "nodes in bitcoin network" but not not in blockchain?
Zergatul
CC BY-SA 3.0
2017-07-12T18:58:49.577Z
Yes you are right, I mean in bitcoin network @Zergatul
ShakibaZar
<buy-bitcoins>
What if a malicious owns more than half of the nodes in bitcoin network?
ShakibaZar
# What if a malicious owns more than half of the nodes in bitcoin network?

(Asked by: username_0 on 2017-07-12)

my question is simply What if a malicious owns more than half of the nodes in bitcoin network? she can simply fraud then. isn't there any algorithm to prevent someone from having more than half of nodes in bitcoin network?

**Tags:** buy-bitcoins

> **Comments:**
> **username_1**: maybe you mean "nodes in bitcoin network" but not not in blockchain?  
> **username_0**: Yes you are right, I mean in bitcoin network @username_1  

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## 2 answers

### Answer by username_2 on 2017-07-12. Score: 2 | Accepted answer

No. The 51% hack is considered one of the main ways a hacker could control the network. However, it is almost completely implausible because of the sheer amount of power that would be required to have 51%. For example, the total hash rate of the network is currently 6.09 Exahashes per second. So, if a hacker wanted to take control of the network, he would need to buy about 6.1 Exahashes per second of hash power. An antminer S9, for 3,000 dollars, gives you 14 terrahashes per second. Thus, the supposed hacker would need to buy 435,000 Antminer S9's which would cost 1.305 billion. That's not even considering the growth rate of the network and the sheer amount of space and energy required to host all of those Antminers.

> **Comments:**
> **username_3**: No need by buy ASICs to do 51%-attack. Just create a mining pool with 5% bonus available for withdraw after a year of mining. :)  
> **username_4**: I believe the question was referring to number of *nodes* not mining power?  
> **username_2**: I should have clarified it, yes. But the mining power is the number that actually matters I believe.  
> **username_4**: Yes you are correct, but I will post another answer to clarify that for everyone  

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### Answer by username_4 on 2017-07-12. Score: 2

In verifying transactions, it is not the *number* of nodes that an attacker owns, but the hashing power which matters. Having many bad nodes (Sybil attack) could affect the network in other ways such as not relaying all transactions, etc, but you can't trick an honest node into accepting a different blockchain without mining enough blocks for it to become the largest chain in the network, and that requires more than 51% of the hashing power to race against the rest of the network.


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