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I’m exaggerating a lot here, but one concern people have with quantum computing is what if it breaks all cryptography, but doesn’t help us solve “useful” proble

I’m exaggerating a lot here, but one concern people have with quantum computing is what if it breaks all cryptography, but doesn’t help us solve “useful” problems. The what if is pulling a lot of weight here but I hope it makes my point.

zelphirkalt 2y ago
I guess that would be about asymmetrical encryption. Which is today indispensable for a lot of infrastructure. Still, there's symmetrical encryption, which is mostly untouched by Shor's algorithm.
- jfengel 2y ago
  Symmetrical encryption requires key distribution, which presents new areas of attack. Though there is also quantum key distribution, which will probably be solved as soon as quantum algorithms can break classical encryption.
  - pclmulqdq 2y ago
    QKD is essentially a layer 1 protocol. It's not in the same realm as symmetric key establishment. That said, there are quantum-resistant key establishment algorithms out there, and more likely one of them will be selected.
  - fsh 2y ago
    QKD also needs key distribution to prevent MITM attacks. It behaves almost exactly like a classical stream cypher, except that it cannot be package-routed, is many orders of magnitude slower, and is prone to side-channel attacks.
- whysosadge 2y ago
  Depending on the use case. Symmetric crypto varies. For example, if your source only has 100 bits of classical entropy. For example, fuzzy extractors. It becomes manageable to break it now with a QC.
adastra22 2y ago
Quantum computing is extremely useful for accurate computational chemistry, which impacts everything from materials science to medicine.
- gaugefield 2y ago
  That statement alone does not paint the whole picture. It also has to be better in terms of some metric (e.g. accuracy, computation time, size of molecules simulatable) when compared to classical ones.
  - adastra22 2y ago
    It makes accurate simulation of quantum mechanical systems of relevance (e.g. molecules) even possible. DFT simulations are full of approximations just to get them to be able to run on classical supercomputers. Nobody does a full solution of Schrödinger's equation. With a sufficiently sized quantum computer, you could.

zelphirkalt 2y ago

I guess that would be about asymmetrical encryption. Which is today indispensable for a lot of infrastructure. Still, there's symmetrical encryption, which is mostly untouched by Shor's algorithm.

jfengel 2y ago
Symmetrical encryption requires key distribution, which presents new areas of attack. Though there is also quantum key distribution, which will probably be solved as soon as quantum algorithms can break classical encryption.
- pclmulqdq 2y ago
  QKD is essentially a layer 1 protocol. It's not in the same realm as symmetric key establishment. That said, there are quantum-resistant key establishment algorithms out there, and more likely one of them will be selected.
- fsh 2y ago
  QKD also needs key distribution to prevent MITM attacks. It behaves almost exactly like a classical stream cypher, except that it cannot be package-routed, is many orders of magnitude slower, and is prone to side-channel attacks.
whysosadge 2y ago
Depending on the use case. Symmetric crypto varies. For example, if your source only has 100 bits of classical entropy. For example, fuzzy extractors. It becomes manageable to break it now with a QC.

adastra22 2y ago

Quantum computing is extremely useful for accurate computational chemistry, which impacts everything from materials science to medicine.

gaugefield 2y ago
That statement alone does not paint the whole picture. It also has to be better in terms of some metric (e.g. accuracy, computation time, size of molecules simulatable) when compared to classical ones.
- adastra22 2y ago
  It makes accurate simulation of quantum mechanical systems of relevance (e.g. molecules) even possible. DFT simulations are full of approximations just to get them to be able to run on classical supercomputers. Nobody does a full solution of Schrödinger's equation. With a sufficiently sized quantum computer, you could.