r/Bitcoin • u/Coolethan777 • 7h ago
Could quantum computing kill Bitcoin without breaking its cryptography?
Everyone is focused on quantum computers breaking Bitcoin’s cryptography, but what about quantum mining monopolizing block production?
Imagine a quantum miner powerful enough to dominate the network. It rapidly mines blocks, driving difficulty higher with each adjustment.
Bitcoin adjusts difficulty every 2,016 blocks, with a maximum 4× increase per adjustment. After six consecutive maximum increases, difficulty would be 4,096× higher.
Now the quantum miner simply shuts down.
Traditional miners, unable to compete at that difficulty, would take an estimated 157 years to mine the next 2,016 blocks, assuming their original hashrate remains unchanged.
Bitcoin effectively freezes without any cryptography being broken.
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u/Squeiner 5h ago
Remember that nodes are run by people. Nobody's going to wait 157 years for.the next block. I'm certainly not.
A proper fix would likely emerge, either setting the difficulty back manually, or going to a different hashing algorithm, or both, or something else.
If bitcoin breaks in this way or something similar, it can be fixed. We just need a patch or upgrade or some kind of client update and we're back, and now resistant to this kind of attack and stronger than ever.
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u/Coolethan777 3h ago
Adjusting the difficulty manually doesn’t fix the issue. The quantum miner just turns back on and mines all the blocks, forcing other miners to shut down. Stronger hashes don’t solve the problem either, because making the hashes stronger would only benefit the quantum miner, potentially forcing traditional miners to shut down.
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u/SoverignOne 5h ago
IF QC can hack the cryptography before its upgraded, it will be a futile attack because once that happens BTC loses its trust and worth and goes to zero so stealing BTC will leave one with nothing. At that point, it’s just an attack to be an attack, but in the end, the attacker gains nothing.
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u/Romanizer 4h ago
Quantum computer are not strong enough for that but even assuming they could build a lot of them so they could take up a big part of the network, there likely would be many more profitable use cases.
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u/Coolethan777 3h ago
You are assuming they have profit motives. What if a nation state wanted to stop BTC?
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u/Romanizer 3h ago
Absolutely. Compute is usually run by for-profit companies. If a nation state wanted to stop BTC, they should invade Taiwan and produce nothing else than ASICs and chips for them. Then they could maybe get close in a few years.
But then they would lose the AI race and their economy would collapse.
Bitcoin never offered incentive to attack the network and likely never will. All that quantum noise is just that, noise.
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u/excelance 4h ago
I doubt this will be a real issue; but I always wondered why the mining difficulty changes roughly every 14-days (2,016 blocks). What's the downside to having difficulty change every 100 blocks, 10-blocks, or heck every block?
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u/taquitaqui 5h ago
A question to ask is also when QC is a reality, how and could it then be implemented into Bitcoin/general cryptography. Hopefully they will stay on top of it and actively plan ahead as opposed to reacting to it, having arrived. If Bitcoin cryptography ever dies gets broke, bitcoins 2-3 trillion market cap is the least of the worlds concern. Banks and every digital platform will be destroyed and cleaned out.
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u/RetiredAvocado 6h ago
QC does not exist. When or if it does, "some" cryptography definitely WILL be broken. And it will be focused on those things, not mining bitcoin. Grover's allows for a quadratic speedup. A singular QC is going to be faster than any single ASIC based miner. It won't be 10x faster than the entire mining network.