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Why would Bitmain shut down their customers' hardware? It's a sure way to kill their (quite successful) brand. But even if it happens, all you have to do is up

Why would Bitmain shut down their customers' hardware? It's a sure way to kill their (quite successful) brand. But even if it happens, all you have to do is update the firmware again, and keep mining. But let's imagine someone actually does shut down 70% of the mining power. What's the real consequence? Blocks will be mined somewhat slower (but not even close to 3 times slower) till the difficulty self-corrects. In the very worst case that will take 2016 blocks, or 14 days.

__jal 10y ago
> Why would Bitmain shut down their customers' hardware? I'm not them, so I don't know. That sort of mechanism doesn't build itself, though, so I have to imagine they have at least one scenario in mind... Also, reason #547 I don't take Bitcoin seriously. One vendor gets popular, and 70% of your infra depends on a watchdog not malfunctioning. That is not a sign of a stable ecosystem.
- ekimekim 10y ago
  > That sort of mechanism doesn't build itself, though, so I have to imagine they have at least one scenario in mind... Most likely this is an attempt at DRM, an ability to remotely shut down any units they've deemed infringing or violating their TOS or haven't paid a renewed licencing fee or whatever (I don't know what their business model is)
  - mikekchar 10y ago
    Much more likely IMHO is that it is a testing facility. When you are building equipment that is intended to work in a network mesh, being able to setup, tear down and simulate network problems quickly is important. It should never be in production code, but you know what engineers are like when they are pushed for deadlines.
clarkmoody 10y ago
This comes into play in the event of a contentious hard fork. Since the miners send their MAC, the parent can look up the customer from sales records. If that customer is against the parent's position in the hard fork, they turn off their machines. The "enemy" fork loses massive hash power at a critical moment.
- kzrdude 10y ago
  It becomes a bigger issue just because that conflict is so infected. No room for honest mistakes, then.
Jaecen 10y ago
When the difficulty is adjusted, the next difficulty adjustment is set to happen after the number of blocks the current hash rate will complete in two weeks. If the hash rate drops, it will take more than two weeks to adjust again.
gizmo686 10y ago
If you are an affected miner, then you have a direct financial cost. This is also a motiviation for other miners to exploit this, as they can take advantage of the decreased difficulty to mine more blocks themselves. It is also a network security concern. Bitcoin's 50% security definition is already pretty weak compared to most crypto security definitions. If you have a seperate attack that can take out 70% of the network, then you only need to have power equal to that of 30% of the network to launch a double spend attack. By itself this might not be enough to make an attack feasible, but if the network is vulnerable to enough of these attacks at the same time, they would compound and a succesfully double spend becomes possible.
0x0 10y ago
If you can shut down up to 70% of the mining power, it would make mounting a 51% attack incredibly easy. It would also mean whoever controls the remaining mining power is in for a treat with block rewards for a while.
- olegkikin 10y ago
  51% attack would require a collusion of the large group of the miners, and, if successful, will likely cause a massive price drop. Which is the last thing miners want. P.S. And btw, it's >50% attack, not 51% attack. You don't need that whole extra percent.
  - int_19h 10y ago
    > 51% attack would require a collusion of the large group of the miners If you can shut off 70% of all the miners (because they run backdoored hardware), then you only need >50% of the remaining 30%, no? Which should be a lot easier.
- MertsA 9y ago
  Whoever was left mining after that wouldn't get more block rewards unless it was something more extreme like bricking 70% of miners instead of just disabling them for a short amount of time. They would be able to mine 100% of blocks but there would be a lot more time between blocks until the next difficulty change. Unless it's something that would permanently break miners it wouldn't last long enough to earn the attackers anything extra in terms of extra blocks mined but facing congestion all blocks would be filled with extra high fee transactions so there would be some BTC to gain, but not from the normal block reward.
Phlarp 10y ago
It might open a window allowing a large intact miner to double spend. If bitmain (or an attacker) took down 70% of the mining power but one miner either didn't use any bitmain hardware or was otherwise protected from the shutdown they would very likely have over 50% of the remaining hashrate. This could give them control over the blockchain until other miners got back online and their share of the overall hashrate dropped below 50% again, worse yet a difficulty correction won't fix things if other miners are slow to recover.
- olegkikin 10y ago
  Who is that "large intact miner"?
  - Phlarp 10y ago
    I didn't have a specific miner in thought while commenting, but in this instance it could be 1) a miner that does not use any bitmain equipment 2) a miner that uses bitmain equipment but has otherwise preemptively mitigated this attack vector or 3) Bitmain themselves acting maliciously.
    - olegkikin 10y ago
      Yeah, so can you name that mysterious miner? You can see the big ones here, for instance: https://blockchain.info/blocks https://blockchain.info/blocks Which one is it?
      - Phlarp 10y ago
        I have absolutely zero insight into the security practices of bitcoin mining operations. I suspect at least some of them take it seriously considering the amount of money involved.
  - xg15 9y ago
    Bitmain themselves?
desdiv 10y ago
>In the very worst case that will take 2016 blocks, or 14 days. The difficulty self-corrects every 2016 blocks, or 14 days if there's no major change in the hashrate. If the hashrate drops by 70% then the worst case is 14 / 30% = 46 days of slow mining until the next correction. I agree with your overall point; just here to point out the math error.
- olegkikin 10y ago
  I think you are wrong, blocks will not be mined 3 times slower just because the global hashrate dropped by 70%. Think of it as a race, many participants are running the distance with slightly different speeds. You randomly remove 70% of the runners, and your new top runner will be likely just a tiny bit behind the previous top runner, if at all.
  - nissimk 10y ago
    No, it's not a race to a finish line, it's a race to find a random number that when placed in the block header hashes to a value that is less than the difficulty. The difficulty is adjusted as desdiv said above based on the network performance in the previous period. When network hashrate increases significantly, the next difficulty adjustment happens sooner and if the hashrate dropped dramatically then it would happen slower. The better analogy would be a race to turn over stones looking for the one with the secret on the back but the number of stones was adjusted for the previous number of searchers and now with fewer searchers it will take longer for any of them to find it.
  - stordoff 10y ago
    I don't think your runner analogy holds up, as the difficulty change essentially effects the global work required (lower chance of finding a suitable random value). It's more like measuring the total distance run by all runners - reaching the same total distance with less runners would take significantly longer.
  - MertsA 9y ago
    It's not a race, it's a scavenger hunt. If you remove half of the searchers you'll take twice as long.
pmorici 9y ago
There is no reason to think they would this is just another part of the long running smear campaign against Bitmain by a collective of Bitcoin Core developers calling themselves the "Dragon's Den" so called because that is the name of the slack chat room where they plan their character assassination campaigns against people and companies who disagree with them.
- hutzlibu 9y ago
  So you are saying "Dragon's Den" is responsible for the backdoor? How?
  - pmorici 9y ago
    I'm saying they are responsible for the messaging and pushing this as some kind of evil plot. The Antminer firmware is opensource and has been on GitHub for anyone to inspect for quite sometime.
h1d 9y ago
Why does it have to be Bitmain to shutdown the miners? How about a random hacker who gained control of that home server or the domain? Shorting 100x before shutting them down sounds like a good incentives for those people.

__jal 10y ago

> Why would Bitmain shut down their customers' hardware? I'm not them, so I don't know. That sort of mechanism doesn't build itself, though, so I have to imagine they have at least one scenario in mind... Also, reason #547 I don't take Bitcoin seriously. One vendor gets popular, and 70% of your infra depends on a watchdog not malfunctioning. That is not a sign of a stable ecosystem.

ekimekim 10y ago
> That sort of mechanism doesn't build itself, though, so I have to imagine they have at least one scenario in mind... Most likely this is an attempt at DRM, an ability to remotely shut down any units they've deemed infringing or violating their TOS or haven't paid a renewed licencing fee or whatever (I don't know what their business model is)
- mikekchar 10y ago
  Much more likely IMHO is that it is a testing facility. When you are building equipment that is intended to work in a network mesh, being able to setup, tear down and simulate network problems quickly is important. It should never be in production code, but you know what engineers are like when they are pushed for deadlines.

clarkmoody 10y ago

This comes into play in the event of a contentious hard fork. Since the miners send their MAC, the parent can look up the customer from sales records. If that customer is against the parent's position in the hard fork, they turn off their machines. The "enemy" fork loses massive hash power at a critical moment.

kzrdude 10y ago
It becomes a bigger issue just because that conflict is so infected. No room for honest mistakes, then.

Jaecen 10y ago

When the difficulty is adjusted, the next difficulty adjustment is set to happen after the number of blocks the current hash rate will complete in two weeks. If the hash rate drops, it will take more than two weeks to adjust again.

gizmo686 10y ago

If you are an affected miner, then you have a direct financial cost. This is also a motiviation for other miners to exploit this, as they can take advantage of the decreased difficulty to mine more blocks themselves. It is also a network security concern. Bitcoin's 50% security definition is already pretty weak compared to most crypto security definitions. If you have a seperate attack that can take out 70% of the network, then you only need to have power equal to that of 30% of the network to launch a double spend attack. By itself this might not be enough to make an attack feasible, but if the network is vulnerable to enough of these attacks at the same time, they would compound and a succesfully double spend becomes possible.

0x0 10y ago

If you can shut down up to 70% of the mining power, it would make mounting a 51% attack incredibly easy. It would also mean whoever controls the remaining mining power is in for a treat with block rewards for a while.

olegkikin 10y ago
51% attack would require a collusion of the large group of the miners, and, if successful, will likely cause a massive price drop. Which is the last thing miners want. P.S. And btw, it's >50% attack, not 51% attack. You don't need that whole extra percent.
- int_19h 10y ago
  > 51% attack would require a collusion of the large group of the miners If you can shut off 70% of all the miners (because they run backdoored hardware), then you only need >50% of the remaining 30%, no? Which should be a lot easier.
MertsA 9y ago
Whoever was left mining after that wouldn't get more block rewards unless it was something more extreme like bricking 70% of miners instead of just disabling them for a short amount of time. They would be able to mine 100% of blocks but there would be a lot more time between blocks until the next difficulty change. Unless it's something that would permanently break miners it wouldn't last long enough to earn the attackers anything extra in terms of extra blocks mined but facing congestion all blocks would be filled with extra high fee transactions so there would be some BTC to gain, but not from the normal block reward.

Phlarp 10y ago

It might open a window allowing a large intact miner to double spend. If bitmain (or an attacker) took down 70% of the mining power but one miner either didn't use any bitmain hardware or was otherwise protected from the shutdown they would very likely have over 50% of the remaining hashrate. This could give them control over the blockchain until other miners got back online and their share of the overall hashrate dropped below 50% again, worse yet a difficulty correction won't fix things if other miners are slow to recover.

olegkikin 10y ago
Who is that "large intact miner"?
- Phlarp 10y ago
  I didn't have a specific miner in thought while commenting, but in this instance it could be 1) a miner that does not use any bitmain equipment 2) a miner that uses bitmain equipment but has otherwise preemptively mitigated this attack vector or 3) Bitmain themselves acting maliciously.
  - olegkikin 10y ago
    Yeah, so can you name that mysterious miner? You can see the big ones here, for instance: https://blockchain.info/blocks https://blockchain.info/blocks Which one is it?
    - Phlarp 10y ago
      I have absolutely zero insight into the security practices of bitcoin mining operations. I suspect at least some of them take it seriously considering the amount of money involved.
- xg15 9y ago
  Bitmain themselves?

desdiv 10y ago

>In the very worst case that will take 2016 blocks, or 14 days. The difficulty self-corrects every 2016 blocks, or 14 days if there's no major change in the hashrate. If the hashrate drops by 70% then the worst case is 14 / 30% = 46 days of slow mining until the next correction. I agree with your overall point; just here to point out the math error.

olegkikin 10y ago
I think you are wrong, blocks will not be mined 3 times slower just because the global hashrate dropped by 70%. Think of it as a race, many participants are running the distance with slightly different speeds. You randomly remove 70% of the runners, and your new top runner will be likely just a tiny bit behind the previous top runner, if at all.
- nissimk 10y ago
  No, it's not a race to a finish line, it's a race to find a random number that when placed in the block header hashes to a value that is less than the difficulty. The difficulty is adjusted as desdiv said above based on the network performance in the previous period. When network hashrate increases significantly, the next difficulty adjustment happens sooner and if the hashrate dropped dramatically then it would happen slower. The better analogy would be a race to turn over stones looking for the one with the secret on the back but the number of stones was adjusted for the previous number of searchers and now with fewer searchers it will take longer for any of them to find it.
- stordoff 10y ago
  I don't think your runner analogy holds up, as the difficulty change essentially effects the global work required (lower chance of finding a suitable random value). It's more like measuring the total distance run by all runners - reaching the same total distance with less runners would take significantly longer.
- MertsA 9y ago
  It's not a race, it's a scavenger hunt. If you remove half of the searchers you'll take twice as long.

pmorici 9y ago

There is no reason to think they would this is just another part of the long running smear campaign against Bitmain by a collective of Bitcoin Core developers calling themselves the "Dragon's Den" so called because that is the name of the slack chat room where they plan their character assassination campaigns against people and companies who disagree with them.

hutzlibu 9y ago
So you are saying "Dragon's Den" is responsible for the backdoor? How?
- pmorici 9y ago
  I'm saying they are responsible for the messaging and pushing this as some kind of evil plot. The Antminer firmware is opensource and has been on GitHub for anyone to inspect for quite sometime.

h1d 9y ago

Why does it have to be Bitmain to shutdown the miners? How about a random hacker who gained control of that home server or the domain? Shorting 100x before shutting them down sounds like a good incentives for those people.