<p>I grasp your question, mining becomes unprofitable so mining hardware is turned off and the difficulty reduces. Then, an attacker coerces miners to turn on their hardware in a bid to attack the network.</p>

<p>This would be difficult to achieve. First, you would have to identify where the mining hardware that is turned off is, identify who it is that operated it and, make contact with them. Then, you would need to convince them to go along with your attack.</p>

<p>As mining is largely anonymous, at best you could potentially source <em>some</em> of the IP's that miners are connecting through. Nothing says that the IP a miner is connecting through is their IP and even less identifies the mining operator working behind a particular IP, and still convince enough to go along with your attack to make up 51% of the hash power. This attack is infeasible.</p>

CC BY-SA 3.0
2018-02-04T09:30:51.583Z
2018-02-04T09:30:51.583Z
Willtech
<p>This is a tautology. The hardware used to build a longer chain (a 51% attack) is hardware that is profitable to mine with. Thus you cannot use unprofitable hardware.</p>

CC BY-SA 3.0
2017-12-05T13:16:47.803Z
Well, yes, but it might be profitable for the wrong reasons, such as being funded by a government that wants to undermine bitcoin.
Daniel R
CC BY-SA 3.0
2017-12-05T13:18:21.097Z
That happens in a 51% attack in the sense that that hardware could be used to mine and make a profit but instead it is funded by someone else with the scope of attacking the blockchain. (You cannot build a 51% attack with obsolete hardware)
Emil R
CC BY-SA 3.0
2017-12-05T13:23:07.360Z
Yes, but isn't the case today that it is hard to amass the amount of hash power that you need for a 51 % attack? If difficulty goes down drastically, hash power is there, somewhere, and can be powered up easily for malicious reasons.
Daniel R
CC BY-SA 3.0
2017-12-05T13:32:31.163Z
If that were to happen that would be a 51% attack and the solution to that is a pow change.
Emil R
CC BY-SA 3.0
2017-12-05T13:33:38.897Z
Do you mean a pow change such as a change of hashing algorithm rendering all mining hardware useless?
Daniel R
CC BY-SA 3.0
2017-12-05T13:36:01.363Z
yes. that is the only solution we have to a prolonged 51% attack
Emil R
CC BY-SA 3.0
2017-12-05T13:37:56.547Z
Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/69738/discussion-between-daniel-r-and-emil-r).
Daniel R
CC BY-SA 3.0
2017-12-05T13:15:46.097Z
2017-12-05T13:15:46.097Z
Emil R
<p>A not unthinkable scenario is that the Bitcoin price decreases to, say, 10-20% of today's value. This would make mining less profitable, and the difficulty should adapt accordingly.</p>

<p>This should lead to a large amount of unused hash power, that could be made available to some majority attacker. </p>

<p>What are the implications of just knowing that someone (although unlikely) could be covertly using this hash power to mine a parallel and longer blockchain before difficulty adjusts, causing all sorts of trouble?</p>

<p>Can this scenario be remedied somehow by altering the protocol?</p>

<security><difficulty><hashpower><majority-attack>
What are the implications of a huge amount of unused hash power?
Daniel R
# What are the implications of a huge amount of unused hash power?

(Asked by: username_0 on 2017-12-05)

A not unthinkable scenario is that the Bitcoin price decreases to, say, 10-20% of today's value. This would make mining less profitable, and the difficulty should adapt accordingly.

This should lead to a large amount of unused hash power, that could be made available to some majority attacker.

What are the implications of just knowing that someone (although unlikely) could be covertly using this hash power to mine a parallel and longer blockchain before difficulty adjusts, causing all sorts of trouble?

Can this scenario be remedied somehow by altering the protocol?

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


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## 2 answers

### Answer by username_1 on 2018-02-04. Score: 2 | Accepted answer

I grasp your question, mining becomes unprofitable so mining hardware is turned off and the difficulty reduces. Then, an attacker coerces miners to turn on their hardware in a bid to attack the network.

This would be difficult to achieve. First, you would have to identify where the mining hardware that is turned off is, identify who it is that operated it and, make contact with them. Then, you would need to convince them to go along with your attack.

As mining is largely anonymous, at best you could potentially source *some* of the IP's that miners are connecting through. Nothing says that the IP a miner is connecting through is their IP and even less identifies the mining operator working behind a particular IP, and still convince enough to go along with your attack to make up 51% of the hash power. This attack is infeasible.


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### Answer by username_2 on 2017-12-05. Score: 0

This is a tautology. The hardware used to build a longer chain (a 51% attack) is hardware that is profitable to mine with. Thus you cannot use unprofitable hardware.

> **Comments:**
> **username_0**: Well, yes, but it might be profitable for the wrong reasons, such as being funded by a government that wants to undermine bitcoin.  
> **username_2**: That happens in a 51% attack in the sense that that hardware could be used to mine and make a profit but instead it is funded by someone else with the scope of attacking the blockchain. (You cannot build a 51% attack with obsolete hardware)  
> **username_0**: Yes, but isn't the case today that it is hard to amass the amount of hash power that you need for a 51 % attack? If difficulty goes down drastically, hash power is there, somewhere, and can be powered up easily for malicious reasons.  
> **username_2**: If that were to happen that would be a 51% attack and the solution to that is a pow change.  
> **username_0**: Do you mean a pow change such as a change of hashing algorithm rendering all mining hardware useless?  
> **username_2**: yes. that is the only solution we have to a prolonged 51% attack  
> **username_0**: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/69738/discussion-between-username_0-and-username_2-r).  

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