4 ms·

Could bitcoin miners use this to "guess" the next block?

LZ_Khan 2y ago
Yes, but I'm pretty sure the moment this is achieved bitcoin's price will collapse. And the investment required to produce such a machine is undoubtedly in the XX billions.
- TZubiri 2y ago
  "Yes, but I'm pretty sure the moment this is achieved bitcoin's price will collapse." Not necessarily. There's two interpretations to the question: 1. QC would be very efficient and mine efficiently. 2. QC would break SHA and would be able to reverse the hashing function at O(1). In scenario 1. The difficulty would increase. The mining rate globally always stays the same. And the voting power would be distributed amongst the holders of the new compute, this has happened before with ASICs. Usually there's some graduality to it, and the capital is distributed so that there is never a 51% monopoly. It's especially relevant how big the jump is, if the new computer is stronger than all of the existing miners combined, then they get 100% theoretically (although with malice). In that case there would probably be a fork or as you put it, BTC would collapse. However, if you have that power, holding BTC is probably not that important anyway. The actual compute is worth more. On scenario 2. Yes BTC would crash, but then again the actual compute power would be more impactful. BTC would crash but so would encryption, and planes and the world.
  - Solvitieg 2y ago
    > BTC would crash but so would encryption, and planes and the world. Sad to see Bitcoin advocates use this dismissive argument. Centralized systems will update their software as the threat increases. Meanwhile, there are no serious proposals for a quantum-resistance Bitcoin. Some are estimating the update will require a hard fork and take 1 year to update.
    - TZubiri 2y ago
      Not sure I would say I'm a bitcoin advocate, nor whether the argument is dismissive, or what it's supposed to be dismissive.
astrange 2y ago
IIRC Bitcoin is quantum-safe because SHA-256 is quantum-safe.
- chickenbigmac 2y ago
  [dead]
mapmeld 2y ago
Not really. The primary issue with Bitcoin x quantum computers is that older Bitcoin transactions contained a full public key (and not a fingerprint / wallet address), so a quantum computer could manipulate that to make a false signature on wallets including Satoshi's (this would be obvious and detectable if someone starts moving very dormant coins). For the larger network there are some other points where it becomes an issue, but before then you'd need to fix HTTPS web traffic and PGP, too. https://www.deloitte.com/nl/en/services/risk-advisory/perspectives/quantum-computers-and-the-bitcoin-blockchain.html https://www.deloitte.com/nl/en/services/risk-advisory/perspe...
coppsilgold 2y ago
Mining is SHA256 guess-and-check lottery which will be safe from a quantum computer. Bitcoin private keys will become vulnerable with knowledge of the public keys. There is a way to mitigate this - because a bitcoin address is a hash of a public key, a bitcoin protocol change can occur whereas the public key becomes a secret and the signature is a zero-knowledge-proof (ZKP) of the prescribed transformation of secret -> address. These signatures are going to be big however, and so the fees will be very high.

Yes, but I'm pretty sure the moment this is achieved bitcoin's price will collapse. And the investment required to produce such a machine is undoubtedly in the XX billions.

TZubiri 2y ago
"Yes, but I'm pretty sure the moment this is achieved bitcoin's price will collapse." Not necessarily. There's two interpretations to the question: 1. QC would be very efficient and mine efficiently. 2. QC would break SHA and would be able to reverse the hashing function at O(1). In scenario 1. The difficulty would increase. The mining rate globally always stays the same. And the voting power would be distributed amongst the holders of the new compute, this has happened before with ASICs. Usually there's some graduality to it, and the capital is distributed so that there is never a 51% monopoly. It's especially relevant how big the jump is, if the new computer is stronger than all of the existing miners combined, then they get 100% theoretically (although with malice). In that case there would probably be a fork or as you put it, BTC would collapse. However, if you have that power, holding BTC is probably not that important anyway. The actual compute is worth more. On scenario 2. Yes BTC would crash, but then again the actual compute power would be more impactful. BTC would crash but so would encryption, and planes and the world.
- Solvitieg 2y ago
  > BTC would crash but so would encryption, and planes and the world. Sad to see Bitcoin advocates use this dismissive argument. Centralized systems will update their software as the threat increases. Meanwhile, there are no serious proposals for a quantum-resistance Bitcoin. Some are estimating the update will require a hard fork and take 1 year to update.
  - TZubiri 2y ago
    Not sure I would say I'm a bitcoin advocate, nor whether the argument is dismissive, or what it's supposed to be dismissive.

astrange 2y ago

IIRC Bitcoin is quantum-safe because SHA-256 is quantum-safe.

chickenbigmac 2y ago
[dead]

mapmeld 2y ago

Not really. The primary issue with Bitcoin x quantum computers is that older Bitcoin transactions contained a full public key (and not a fingerprint / wallet address), so a quantum computer could manipulate that to make a false signature on wallets including Satoshi's (this would be obvious and detectable if someone starts moving very dormant coins). For the larger network there are some other points where it becomes an issue, but before then you'd need to fix HTTPS web traffic and PGP, too. https://www.deloitte.com/nl/en/services/risk-advisory/perspectives/quantum-computers-and-the-bitcoin-blockchain.html https://www.deloitte.com/nl/en/services/risk-advisory/perspe...

coppsilgold 2y ago

Mining is SHA256 guess-and-check lottery which will be safe from a quantum computer. Bitcoin private keys will become vulnerable with knowledge of the public keys. There is a way to mitigate this - because a bitcoin address is a hash of a public key, a bitcoin protocol change can occur whereas the public key becomes a secret and the signature is a zero-knowledge-proof (ZKP) of the prescribed transformation of secret -> address. These signatures are going to be big however, and so the fees will be very high.