What if network hash rate drops?

[GuiltySpark343]

This is never gonna happen, but interesting to think about: if I understand correctly, the bitcoin network difficulty adjusts every 2000 or so blocks, in order to keep blocks being generated once every 10 minutes.

Now at current network hash rate of 130 TH/s (well, more like 150 TH/s recently), the difficulty is 15,605,633. What if suddenly the network hash rate drops by 90%? Although the difficulty will adjust downwards to compensate, that difficulty will take 2000 blocks to "readjust" since it doesn't happen instantaneously.

But if the network hash rate is reduced by 90%, it'll take a looooooong time to generate 2000 blocks before the network difficulty compensates. Is it feasible that a sudden, extended drop in hash rate will lead to a long, dry spell due to the lag time before the difficulty drops in response?

[eleuthria]

This is never gonna happen, but interesting to think about: if I understand correctly, the bitcoin network difficulty adjusts every 2000 or so blocks, in order to keep blocks being generated once every 10 minutes.

Now at current network hash rate of 130 TH/s (well, more like 150 TH/s recently), the difficulty is 15,605,633. What if suddenly the network hash rate drops by 90%? Although the difficulty will adjust downwards to compensate, that difficulty will take 2000 blocks to "readjust" since it doesn't happen instantaneously.

But if the network hash rate is reduced by 90%, it'll take a looooooong time to generate 2000 blocks before the network difficulty compensates. Is it feasible that a sudden, extended drop in hash rate will lead to a long, dry spell due to the lag time before the difficulty drops in response?

While it's doubtful it would ever happen (ASICs have no reason to turn off and they make up roughly half the network now), I'm reminded of when that happened to namecoin.  Before merged mining, people would hop between BTC and NMC based on profitability.  At one point, NMC was hugely ramped up in difficulty, and then it became so unprofitable there was virtually no hashing done, and nearly killing namecoin.  It's the reason merged mining was created, to bootstrap a blockchain to another's hashrate and ensure such massive swings wouldn't happen again.

[k9quaint]

If the hash rate dropped by 90%, then it would take a couple of months to get to the next difficulty adjustment.
Meanwhile, pictures of cats would be viewed on the internet.

I think what would happen would depend more on why 90% of the hash rate disappeared, than the fact that it did.
For instance: If a backlash by governments arresting miners caused it, then Bitcoin itself would be under attack and I don't think people's first worry would be the block reward.

[bcpokey]

If the hash rate dropped by 90%, then it would take a couple of months to get to the next difficulty adjustment.
Meanwhile, pictures of cats would be viewed on the internet.

I think what would happen would depend more on why 90% of the hash rate disappeared, than the fact that it did.
For instance: If a backlash by governments arresting miners caused it, then Bitcoin itself would be under attack and I don't think people's first worry would be the block reward.

There are other effects than just miners not getting their precious bitcoin rewards. Transactions are confirmed by the continued progression of the blockchain. This is the real detriment that alt-coins like the previously mentioned namecoin suffered from.

Imagine that instead of 30min-1hr minutes to confirm your payment, it took 8+ hours, with the real possibility of it taking days. Would that be a good formula for a workable internet payment system? And it would stay that way for months before difficulty adjusted. Admittedly it would only happen due to other extreme circumstances, but just by itself it is bad enough.

[erk]

It will happen at some point. One possible scenario is the cost of mining goes so high in terms of new hardware required to keep up, and the power cost, so much that ASICMINER goes bust, switches off, and hundreds of TH/s suddenly disappears from the network.

Not singling them out, this is a serious possibility with any BTC mining consortium that needs to make a profit to survive.

[suryc]

This is never gonna happen, but interesting to think about: if I understand correctly, the bitcoin network difficulty adjusts every 2000 or so blocks, in order to keep blocks being generated once every 10 minutes.

Now at current network hash rate of 130 TH/s (well, more like 150 TH/s recently), the difficulty is 15,605,633. What if suddenly the network hash rate drops by 90%? Although the difficulty will adjust downwards to compensate, that difficulty will take 2000 blocks to "readjust" since it doesn't happen instantaneously.

But if the network hash rate is reduced by 90%, it'll take a looooooong time to generate 2000 blocks before the network difficulty compensates. Is it feasible that a sudden, extended drop in hash rate will lead to a long, dry spell due to the lag time before the difficulty drops in response?

Also possible, albeit very unlikely, are the potential for intentional sabotage or some kind of natural disaster. I don't know if all of Asic Miners capability is in one location/region, but if it is, that would be dangerous. If for some reason 20% of the network suddenly disappeared that would significantly slow things down. But again its a very improbable scenario.

[andrewsg]

This is never gonna happen, but interesting to think about: if I understand correctly, the bitcoin network difficulty adjusts every 2000 or so blocks, in order to keep blocks being generated once every 10 minutes.

Now at current network hash rate of 130 TH/s (well, more like 150 TH/s recently), the difficulty is 15,605,633. What if suddenly the network hash rate drops by 90%? Although the difficulty will adjust downwards to compensate, that difficulty will take 2000 blocks to "readjust" since it doesn't happen instantaneously.

But if the network hash rate is reduced by 90%, it'll take a looooooong time to generate 2000 blocks before the network difficulty compensates. Is it feasible that a sudden, extended drop in hash rate will lead to a long, dry spell due to the lag time before the difficulty drops in response?

One more thing to note, difficulty cannot go up or down by more than a factor of 4x per retarget, regardless of hash rate changes. So if the hash rate is reduced by 90% right after a retarget (worst case scenario) and then remained constant, one retarget would not be enough to bring the difficulty in line, it would take 2 retargets and unless my math is wrong close to 6 months total time.

[tycho]

This has happened with a number of altcoins recently. Basically the only solution was for them to patch the client and hard fork.

[Rannasha]

This has happened with a number of altcoins recently. Basically the only solution was for them to patch the client and hard fork.

Exactly, the altcoins are a nice micro-environment for testing extreme scenarios such as this.

The outcome has been that some altcoins have implemented much faster difficulty-retargeting (such as every 100 blocks instead of 2000 for example). This greatly mitigates the negative effects of a drop in hashrate, as the difficulty is fixed more quickly.

[ethereumhunter]

If the hash rate dropped by 90%, then it would take a couple of months to get to the next difficulty adjustment.
Meanwhile, pictures of cats would be viewed on the internet.

I think what would happen would depend more on why 90% of the hash rate disappeared, than the fact that it did.
For instance: If a backlash by governments arresting miners caused it, then Bitcoin itself would be under attack and I don't think people's first worry would be the block reward.

i can not imagine if the network hash rate is drop but it might be possible as network is not always get stable so far. i am thinking if this is happen, the difficult is getting lack to incrase and we should see the next difficult in few month like k9quaint said. and i think this will affect with the price too since the miners getting low revenue from the mining itself.

but i wonder, if the situation is like this, can we see the price is stable and stagnan in one range of the price? i think if bitcoin price is stable, the altcoin will be increase soon and this i think is what i wish, i guess 

[Amph]

It will happen at some point. One possible scenario is the cost of mining goes so high in terms of new hardware required to keep up, and the power cost, so much that ASICMINER goes bust, switches off, and hundreds of TH/s suddenly disappears from the network.

Not singling them out, this is a serious possibility with any BTC mining consortium that needs to make a profit to survive.

90% is unlikely no pool is holding a high hasrate like that, no farm either, 10% might be but it's hardly a factor in this, in fact when knc miner went bakrupt nothing really changed, and they were big enough at that time

This has happened with a number of altcoins recently. Basically the only solution was for them to patch the client and hard fork.

we can't even hard fork for 2mb , you think bitcoin will hard fork for this? the consensus will never reach an agrrement

[GMPoison]

Mining is a win-win situation in my eyes.

Price of bitcoin rises? Profit.

Network hash rate drops? Difficulty drops. Profit.

Difficulty rises? People shut their miners off. Difficulty goes down. Profit.