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Tangential question... Seen that many are already moving to QC-resistant cryptography and that more are shifting by the day... I've got a question: what are th

Tangential question... Seen that many are already moving to QC-resistant cryptography and that more are shifting by the day... I've got a question: what are the implications of quantum computers going to be if we consider that the entirety of cryptography will have moved to quantum-resistant cryptography? In other words: I only ever read about quantum computing when it's to talk about breaking cryptography. But what if all cryptography moves to quantum-resistant scheme, all of it... Then what are the uses of quantum computing? Protein folding? Logistics? Basically, so far, quantum computing research has the effect of many companies and projects adding quantum-resistant cryptographic schemes. If, say, we've got a $10 million quantum computer that can break one 256 bit elliptic curve key in an hour... Great, EC is broken. But what if browsers, SSH, auth, etc. just about everything moves to PQ schemes... Then what are those quantum computers useful for? I understand that breaking even a single EC 256 bit key in a few hours on a $$$ machine is a very big deal. But what else are they going to be useful for? For breaking ECC doesn't help humanity. It doesn't bring anything. It only destroys. EDIT: for example I read stuff like: "Estimates are about three years to break a single 256 bit EC key on a 10 000 qbits quantum computer". What's a 10 000 qbits quantum computer going to be used for when everybody shall have moved to quantum-resistant algos?

phicoh 6mo ago
We can assume that organizations like NSA have collected a huge amount of traffic that is protected by RSA or EC. So they well have plenty of use for those quantum computers.
snowwrestler 6mo ago
To start, I am NOT an expert on the underlying technologies. But I have some exposure to the topic at let’s say more like an ecosystem level. There are tons of hypothesized applications for quantum computing based on the expectation it will provide better simulation of quantum effects for e.g. chemistry, and offer major speedups of highly parallel simulation problems like nuclear plasma or some things in finance. Easy to Google to learn more about these. But keeping the focus squarely on the military and intelligence services, one answer to your question is that everyone is not going to switch to post-quantum cryptography instantaneously. It’s going to take a while, especially for a long tail of “infrastructure” type things like networking gear, “internet of things,” industrial sensors, etc. Things that national intelligence services might like to break into to enable breaking into other things. Quantum breaks may also still succeed against stored encrypted data from before the switch to PQ. And for at least a couple decades, national intelligence services have been scaling up their storage resources. So they might have a “backlog” they can work through. Finally, things don’t have to last forever. Everything the military / government builds has an expected lifespan, and it only has to be valuable during that life span. And risks can be rare but huge in national security. So if quantum code-breaking computers only help the NSA learn a few very important things for a limited time, that still might be “worth it” to them. Or if a quantum computer doesn’t break any important cryptography, but helps advance the engineering and enables better quantum computers in the future for other anpplications—again, still might be worth it.

phicoh 6mo ago

We can assume that organizations like NSA have collected a huge amount of traffic that is protected by RSA or EC. So they well have plenty of use for those quantum computers.

snowwrestler 6mo ago

To start, I am NOT an expert on the underlying technologies. But I have some exposure to the topic at let’s say more like an ecosystem level. There are tons of hypothesized applications for quantum computing based on the expectation it will provide better simulation of quantum effects for e.g. chemistry, and offer major speedups of highly parallel simulation problems like nuclear plasma or some things in finance. Easy to Google to learn more about these. But keeping the focus squarely on the military and intelligence services, one answer to your question is that everyone is not going to switch to post-quantum cryptography instantaneously. It’s going to take a while, especially for a long tail of “infrastructure” type things like networking gear, “internet of things,” industrial sensors, etc. Things that national intelligence services might like to break into to enable breaking into other things. Quantum breaks may also still succeed against stored encrypted data from before the switch to PQ. And for at least a couple decades, national intelligence services have been scaling up their storage resources. So they might have a “backlog” they can work through. Finally, things don’t have to last forever. Everything the military / government builds has an expected lifespan, and it only has to be valuable during that life span. And risks can be rare but huge in national security. So if quantum code-breaking computers only help the NSA learn a few very important things for a limited time, that still might be “worth it” to them. Or if a quantum computer doesn’t break any important cryptography, but helps advance the engineering and enables better quantum computers in the future for other anpplications—again, still might be worth it.