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> In the third section I analyze its security model, specifically the cost of mounting a 51% attack on the assumption that hash power is available for rent and

> In the third section I analyze its security model, specifically the cost of mounting a 51% attack on the assumption that hash power is available for rent and doesn't need to be purchased by the attacker. Bitcoin mining requires special devices (ASICs). These ASICs would lose their value if Bitcoin lost its value. Given this fact, why would anyone rent them out, or rent out the hash power?

pcthrowaway 4y ago
If your hash power typically translates to $X per day and someone offers you 2X $ to rent the hash power for a day, I suspect most people would rent them out
- yellowapple 4y ago
  Why would someone offer you that, though?
JumpCrisscross 4y ago
> mining requires special devices (ASICs) Profitable mining does. If you’re looking to make money, you need ASICs. If you’re just looking to disrupt the network, e.g. for military purposes, commandeering a cloud or two would do.
- wyager 4y ago
  > commandeering a cloud or two would do. No; The ASICs are orders of magnitude faster and more efficient per dollar. Every GPU on earth couldn't touch the bitcoin hashrate.
  - JumpCrisscross 4y ago
    > ASICs are orders of magnitude faster and more efficient per dollar Every supercomputer in either the U.S. or China plus its cloud resources would be able to mount a 51% attack. And this isn’t counting e.g. the NSA or GCHQ’s supercomputers, which are optimised for code cracking.
    - overthrow 4y ago
      Remember that general-purpose computers use orders of magnitude more energy than specialized hardware for the same task. So if bitcoin uses (say) 0.05% of energy globally, matching the hashrate using general-purpose hardware (assuming an alternate reality where the planet has enough hardware for someone to attempt this) would require something like 5% of global energy usage. Diverting that much energy away from the rest of the world is not even remotely feasible.
      - JumpCrisscross 4y ago
        > would require something like 5% of global energy usage Fair enough, supercomputers + cloud was optimistic. They can’t do 40 zettaflops. Half of that, worst case, we could, though not triviallt. For bursts at a time. (Worst case because the math supercomputers designed to break encryption do is similar to that required to break Bitcoin.) Practically speaking, were we to do this, we’d procure the ASICs. (And target in-jurisdiction mining, lowering the hurdle.) No private party is particularly incentivised to launch such an attack de novo. We may never need to actually attack: a law appropriating tens of billions to create a crypto deterrent would crash prices on its own.
        overthrow 4y ago
        > a law appropriating tens of billions to create a crypto deterrent would crash prices on its own Doubt that. All that would happen is driving the industry underground or overseas. It wouldn't be the first time a government overplayed its hand and failed to acknowledge that bitcoin is a global technology. https://data.nasdaq.com/data/BCHAIN/HRATE-bitcoin-hash-rate https://data.nasdaq.com/data/BCHAIN/HRATE-bitcoin-hash-rate That isn't slowing down. I have exactly 0 faith that governments across the world could start from scratch and cooperate to outpace and then surpass the private sector in a chip fabrication project, no matter how many billions they throw at it.
        JumpCrisscross 4y ago
        > cooperate to outpace and then surpass the private sector in a chip fabrication project You move to seize it. ASICS are manufactured in China and among American allies.
medellin 4y ago
51% of the bitcoin mining hashing power being available for rent is so far fetched that it’s silly to even consider as a valid critique
- ursuscamp 4y ago
  The author really undersells how difficult/nearly impossible this is and will be for a long time, at the very least. If the market transfers successfully from miner subsidy to transaction fees, then it will always be nearly impossible.
osigurdson 4y ago
>> Bitcoin mining requires special devices (ASICs) Nitpick: Any computer can mine bitcoin. Economic bitcoin mining requires special devices.
- latchkey 4y ago
  My favorite way to mine bitcoin! https://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html https://www.righto.com/2014/09/mining-bitcoin-with-pencil-an...

pcthrowaway 4y ago

If your hash power typically translates to $X per day and someone offers you 2X $ to rent the hash power for a day, I suspect most people would rent them out

yellowapple 4y ago
Why would someone offer you that, though?

JumpCrisscross 4y ago

> mining requires special devices (ASICs) Profitable mining does. If you’re looking to make money, you need ASICs. If you’re just looking to disrupt the network, e.g. for military purposes, commandeering a cloud or two would do.

wyager 4y ago
> commandeering a cloud or two would do. No; The ASICs are orders of magnitude faster and more efficient per dollar. Every GPU on earth couldn't touch the bitcoin hashrate.
- JumpCrisscross 4y ago
  > ASICs are orders of magnitude faster and more efficient per dollar Every supercomputer in either the U.S. or China plus its cloud resources would be able to mount a 51% attack. And this isn’t counting e.g. the NSA or GCHQ’s supercomputers, which are optimised for code cracking.
  - overthrow 4y ago
    Remember that general-purpose computers use orders of magnitude more energy than specialized hardware for the same task. So if bitcoin uses (say) 0.05% of energy globally, matching the hashrate using general-purpose hardware (assuming an alternate reality where the planet has enough hardware for someone to attempt this) would require something like 5% of global energy usage. Diverting that much energy away from the rest of the world is not even remotely feasible.
    - JumpCrisscross 4y ago
      > would require something like 5% of global energy usage Fair enough, supercomputers + cloud was optimistic. They can’t do 40 zettaflops. Half of that, worst case, we could, though not triviallt. For bursts at a time. (Worst case because the math supercomputers designed to break encryption do is similar to that required to break Bitcoin.) Practically speaking, were we to do this, we’d procure the ASICs. (And target in-jurisdiction mining, lowering the hurdle.) No private party is particularly incentivised to launch such an attack de novo. We may never need to actually attack: a law appropriating tens of billions to create a crypto deterrent would crash prices on its own.
      - overthrow 4y ago
        > a law appropriating tens of billions to create a crypto deterrent would crash prices on its own Doubt that. All that would happen is driving the industry underground or overseas. It wouldn't be the first time a government overplayed its hand and failed to acknowledge that bitcoin is a global technology. https://data.nasdaq.com/data/BCHAIN/HRATE-bitcoin-hash-rate https://data.nasdaq.com/data/BCHAIN/HRATE-bitcoin-hash-rate That isn't slowing down. I have exactly 0 faith that governments across the world could start from scratch and cooperate to outpace and then surpass the private sector in a chip fabrication project, no matter how many billions they throw at it.
        JumpCrisscross 4y ago
        > cooperate to outpace and then surpass the private sector in a chip fabrication project You move to seize it. ASICS are manufactured in China and among American allies.

medellin 4y ago

51% of the bitcoin mining hashing power being available for rent is so far fetched that it’s silly to even consider as a valid critique

ursuscamp 4y ago
The author really undersells how difficult/nearly impossible this is and will be for a long time, at the very least. If the market transfers successfully from miner subsidy to transaction fees, then it will always be nearly impossible.

osigurdson 4y ago

>> Bitcoin mining requires special devices (ASICs) Nitpick: Any computer can mine bitcoin. Economic bitcoin mining requires special devices.

latchkey 4y ago
My favorite way to mine bitcoin! https://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html https://www.righto.com/2014/09/mining-bitcoin-with-pencil-an...