Comment by phicoh
4 hours ago
What surprises me is how non-linear this argument is. For a classical attack on, for example RSA, it is very easy to a factor an 8-bit composite. It is a bit harder to factor a 64-bit composite. For a 256-bit composite you need some tricky math, etc. And people did all of that. People didn't start out speculating that you can factor a 1024-bit composite and then one day out of the blue somebody did it.
The weird thing we have right now is that quantum computers are absolutely hopeless doing anything with RSA and as far as I know, nobody even tried EC. And that state of the art has not moved much in the last decade.
And then suddenly, in a few years there will be a quantum computer that can break all of the classical public key crypto that we have.
This kind of stuff might happen in a completely new field. But people have been working on quantum computers for quite a while now.
If this is easy enough that in a few years you can have a quantum computer that can break everything then people should be able to build something in a lab that breaks RSA 256. I'd like to see that before jumping to conclusions on how well this works.
See https://bas.westerbaan.name/notes/2026/04/02/factoring.html and https://scottaaronson.blog/?p=9665#comment-2029013 which are linked to in the first section of the article.
> Sure, papers about an abacus and a dog are funny and can make you look smart and contrarian on forums. But that’s not the job, and those arguments betray a lack of expertise. As Scott Aaronson said:
> Once you understand quantum fault-tolerance, asking “so when are you going to factor 35 with Shor’s algorithm?” becomes sort of like asking the Manhattan Project physicists in 1943, “so when are you going to produce at least a small nuclear explosion?”
To summarize, the hard part of scalable quantum computation is error correction. Without it, you can't factorize essentially anything. Once you get any practical error correction, the distance between 32-bit RSA and 2048-bit RSA is small. Similarly to how the hard part is to cause a self-sustaining fissile chain reaction, and once you do making the bomb bigger is not the hard part.
This is what the experts know, and why they tell us of the timelines they do. We'd do better not to dismiss them by being smug about our layperson's understanding of their progress curve.
The thing is, producing the right isotopes of uranium is mostly a linear process. It goes faster as you scale up of course, but each day a reactor produces a given amount. If you double the number of reactors you produce twice as much, etc.
There is no such equivalent for qubits or error correction. You can't say, we produce this much extra error correction per day so we will hit the target then and then.
There is also something weird in the graph in https://bas.westerbaan.name/notes/2026/04/02/factoring.html. That graph suggests that even with the best error correction in the graph, it is impossible to factor RSA-4 with less then 10^4 qubits. Which seems very odd. At the same time, Scott Aaronson wrote: "you actually can now factor 6- or 7-digit numbers with a QC". Which in the graph suggests that error rate must be very low already or quantum computers with an insane number of qubits exist.
Something doesn't add up here.
We are stretching the metaphor thin, but surely the progress towards an atomic bomb was not measured only in uranium production, in the same way that the progress towards a QC is not measured only in construction time of the machine.
At the theory level, there were only theories, then a few breakthroughs, then some linear production time, then a big boom.
> Something doesn't add up here.
Please consider it might be your (and my) lack of expertise in the specific sub-field. (I do realize I am saying this on Hacker News.)
You can already factor a 6 digit number with a QC, but not with an algorithm that scales polynomially. The graph linked is for optimized variants of Shor's algorithm.
> produce at least a small nuclear explosion
The Manhattan Project scientists actually did this before anybody broke ground at Los Alamos. It was called the Chicago Pile. And if the control rods were removed and the SCRAM disabled, it absolutely would have created a "small nuclear explosion" in the middle of a major university campus.
Given the level of hype and how long it's been going on, I think it's totally reasonable for the wider world to ask the quantum crypto-breaking people to build a Chicago Pile first.
https://en.wikipedia.org/wiki/Chicago_Pile-1
TIL about the Chicago Pile! (I don't know enough about the physics to tell if it could have indeed exploded.)
> On 2 December 1942
https://en.wikipedia.org/wiki/Chicago_Pile-1
> on July 16, 1945
https://en.wikipedia.org/wiki/Trinity_(nuclear_test)
Two years and a half. This is still a good metaphor for "once you can make a small one, the large one is not far at all."
What? No. No matter what anybody did with the Chicago Pile, it would never have produced a small version of a nuclear detonation.
His article specifically mentions that the threat is with the public key exchange, not the encryption that happens after the key exchange.
IIRC the largest number factored still remains 21