<p>From <a href="https://bitcoin.stackexchange.com/questions/658/what-can-an-attacker-with-51-of-hash-power-do?rq=1">What can an attacker with 51% of hash power do?</a></p>

<blockquote>
  <p>Prevent some or all other generators from getting any generations</p>
</blockquote>

<p>So, yes. However, it doesn't immediately give him more mining income. Once the block readjustment happens two to six weeks or so after the attack, the bitcoin network will notice that far fewer blocks were made, and the difficulty will go down.</p>

CC BY-SA 3.0
2013-04-20T19:38:58.753Z
If I understand your answer correctly, you're saying that the only way to tell when it's no longer worth trying to mine any more coins is to look at the new adjusted difficulty level. Is that right? I was thinking more like if you're generating valid blocks and they're still getting rejected then maybe it's time to quit mining. But how long would it take for the rest of the 49% to notice this? I mean, is there a formula?
Manish
CC BY-SA 3.0
2013-04-20T19:43:45.180Z
Also, what if it's not an external attack but rather an internal buyout (i.e. a big company just bought 51% of the hash power)? In this case there's no new hash power added to the network.
Manish
CC BY-SA 3.0
2013-04-20T20:02:57.197Z
@Manish `only way to tell when` I think a better way would be to look at all of the pool operators now complaining that they're not making any money. `Also, what if it's not an external attack but rather an internal buyout` Can't be detected purely by looking at the network.
Nick ODell
CC BY-SA 3.0
2013-04-19T17:02:06.527Z
2013-04-19T17:02:06.527Z
2017-04-13T12:47:36.647Z
Nick ODell
<p>Remember that one would have to gain over 400 petaflops of processing power to gain 51% of the network. The top ten supercomputers in the world combined aren't even powerful enough:</p>

<p><a href="http://bitcoinwatch.com/" rel="nofollow">http://bitcoinwatch.com/</a></p>

<p><a href="http://www.top500.org/lists/2012/11/" rel="nofollow">http://www.top500.org/lists/2012/11/</a></p>

CC BY-SA 3.0
2013-04-19T19:08:28.087Z
Note that flops stands for FLOating Point operations per Second, and is perhaps not the best measure of a mining algorithm that uses no floating point operations.
Nick ODell
CC BY-SA 3.0
2013-04-20T02:37:25.197Z
You and your semantics. I'm just trying to demonstrate that taking the network down via a 51% attack isn't going to happen
Charles Hoskinson
CC BY-SA 3.0
2013-04-20T19:28:59.303Z
@CharlesHoskinson George Soros could just buy out most of the miners. Then what? Anyway, I see your point.
Manish
CC BY-SA 3.0
2013-04-20T20:09:36.727Z
Doing so should greatly increase the value of the bitcoin resulting in more people entering the market to mine. Thus Soro's play fails
Charles Hoskinson
CC BY-SA 3.0
2015-06-09T22:59:09.513Z
This misses the question.
Murch
CC BY-SA 3.0
2013-04-19T18:20:50.997Z
2013-04-19T18:20:50.997Z
Charles Hoskinson
<p>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 entirely?</p>

<p>If 51% guarantees 100%, how quickly can this transition (from majority to total control) be expected to occur?</p>

<security><hashpower><majority-attack>
How long does it take to go from 51% hash power to 100% hash power?
Manish
# How long does it take to go from 51% hash power to 100% hash power?

(Asked by: username_0 on 2013-04-19)

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 entirely?

If 51% guarantees 100%, how quickly can this transition (from majority to total control) be expected to occur?

**Tags:** security, hashpower, majority-attack


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## 2 answers

### Answer by username_1 on 2013-04-19. Score: 3

From [What can an attacker with 51% of hash power do?](https://bitcoin.stackexchange.com/questions/658/what-can-an-attacker-with-51-of-hash-power-do?rq=1)

> Prevent some or all other generators from getting any generations

So, yes. However, it doesn't immediately give him more mining income. Once the block readjustment happens two to six weeks or so after the attack, the bitcoin network will notice that far fewer blocks were made, and the difficulty will go down.

> **Comments:**
> **username_0**: If I understand your answer correctly, you're saying that the only way to tell when it's no longer worth trying to mine any more coins is to look at the new adjusted difficulty level. Is that right? I was thinking more like if you're generating valid blocks and they're still getting rejected then maybe it's time to quit mining. But how long would it take for the rest of the 49% to notice this? I mean, is there a formula?  
> **username_0**: Also, what if it's not an external attack but rather an internal buyout (i.e. a big company just bought 51% of the hash power)? In this case there's no new hash power added to the network.  
> **username_1**: @username_0 `only way to tell when` I think a better way would be to look at all of the pool operators now complaining that they're not making any money. `Also, what if it's not an external attack but rather an internal buyout` Can't be detected purely by looking at the network.  

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### Answer by username_2 on 2013-04-19. Score: -3

Remember that one would have to gain over 400 petaflops of processing power to gain 51% of the network. The top ten supercomputers in the world combined aren't even powerful enough:

<http://bitcoinwatch.com/>

<http://www.top500.org/lists/2012/11/>

> **Comments:**
> **username_1**: Note that flops stands for FLOating Point operations per Second, and is perhaps not the best measure of a mining algorithm that uses no floating point operations.  
> **username_2**: You and your semantics. I'm just trying to demonstrate that taking the network down via a 51% attack isn't going to happen  
> **username_0**: @username_2 George Soros could just buy out most of the miners. Then what? Anyway, I see your point.  
> **username_2**: Doing so should greatly increase the value of the bitcoin resulting in more people entering the market to mine. Thus Soro's play fails  
> **username_3**: This misses the question.  

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