They are large, but they're not that slow actually. We've been testing them for almost a decade now. I agree that rushing is bad. That's why we need to start moving now, so that we're not rushing even closer to the deadline.
Leaf certificates don't last long, but root CAs do. An attacker can just mint new certs from a broken root key.
Hopefully many devices can be upgraded to PQ security with a firmware update. Worse than not receiving updates, is receiving malicious firmware updates, which you can't really prevent without upgrading to something safe first.
> An attacker can just mint new certs from a broken root key.
In Chrome at the very least, the certificate not being in the certificate transparency logs should throw errors and report issues to the mothership, and that should detect abuse almost instantly.
You'd still be DoSing an entire certificate authority because a factored CA private key means the entire key is instantly useless, but it wouldn't allow attacks to last long.
Waiting now means rushing even more close to the deadline! We added stats on origin support for post-quantum encryption. Not as much support as browsers of course, but better than I expected. Still a long road (and authentication!). https://radar.cloudflare.com/post-quantum
Don't recognise you from your username, but thanks for the respect. (Update: ah, Vitali! Nice to hear from you.)
If you look back at my writing from 2025 and earlier, I'm on the conservative end of Q-day estimates: 2035 or later. My primary concern then is that migrations take a lot of time: even 2035 is tight.
I'm certainly not an expert on building quantum computers, but what I hear from those that are worries me. Certainly there are open challenges for each approach, but that list is much shorter now than it was a few years ago. We're one breakthrough away from a CRQC.
For me presuming Q-day will happen which is why I categorize that more as a maximalist camp, same as people who believe AGI is inevitable are AI maximalists. I could also be misremembering our conversation, but I thought you had said something like 2029 or 2030 in our 2020 conversation :)?
My concern is that there's so much human and financial capital behind quantum computing that the "experts" have lots of reason to try to convince you that it's going to happen any day now. The cryptographic community is rightly scared by the potential because we don't have any theoretical basis to contradict that QC speedups aren't physically possible, but we also don't have any proof (existence or theoretical) that proves they are actually possible.
The same diagrams that are showing physical q-bits per year or physical qbits necessary to crack some algorithm are the same ones powering funding pitches and that's very dangerous to me - it's very possible it's a tail wagging the dog situation.
The negative evidence here for me is that all the QC supremacy claims to date have constantly evaporated as faster classical algorithms have been developed. This means the score is currently 0/N for a faster than classical QC. The other challenge is we don't know where BQP fits or if it even exists as a distinct class or if we just named a theoretical class of problems that doesn't actually exist as a distinct class. That doesn't get into the practical reality that layering more and more error correction doesn't matter so much when the entire system still decoheres at any number at all relevant for theoretically being able to solve non-trivial problems.
Should we prepare for QC on the cryptography side? I don't know but I'm still less < 10% chance that CRQC happens in the next 20 years. I also look at the other situation - if CRQC doesn't ever happen, we're paying a meaningful cost both in terms of human capital spent hardening systems against it and ongoing in terms of slowing down worldwide communications to protect against a harm that never materializes (not to mention all the funding burned spent chasing building the QC). The problem I'm concerned about is that there's no meaningful funding spent trying to crack whether BQP actually exists and what this complexity class actually looks like.
> I could also be misremembering our conversation, but I thought you had said something like 2029 or 2030 in our 2020 conversation
Think that must've been around 2022. It'd have been me mentioning 2030 regulatory deadlines. So far progress in PQC adoption has been mostly driven by (expected) compliance. Now it'll shift to a security issue again.
> My concern is that there's so much human and financial capital behind quantum computing that the "experts" have lots of reason to try to convince you that it's going to happen any day now.
There've been alarmist publications for years. If it were just some physicists again, I'd have been sceptical. This is the security folks at Google pulling the alarm (among others.)
> [B]ut we also don't have any proof (existence or theoretical) that proves they are actually possible.
The theoretic foundation is pretty basic quantum mechanics. It'd be a big surprise if there'd be a blocker there. What's left is the engineering. The problem is that definite proof means an actual quantum computer... which means it's already too late.
> The other challenge is we don't know where BQP fits
This is philosophy. Even P=NP doesn't imply cryptography is hopeless. If the concrete cost between using and breaking is large enough (even if it's not asymptotically) we can have perfectly secure systems. But this is quite a tangent.
> Should we prepare for QC on the cryptography side?
A 10% chance it happens by 2030, means we'll need to migrate by 2029.
> it and ongoing in terms of slowing down worldwide communications
We've been working hard to make the impact negligible. For key agreement the impact is very small. And with Merkle Tree Certificates we also make the overhead for authentication negligible.
The key will be 40x larger. Not that bad for the certs. It'll be about 15kB extra. Will depend on your use case if that's bad. For video it's fine. But not all browsing is video. At Cloudflare half of the QUIC connections we see transfer less than 8kB from server -> client total. On average 3-4kB of that is already certificates today. That'll probably be quite noticeable. https://blog.cloudflare.com/pq-2025/#do-we-really-care-about...
But do those connections constitute a material amount of total bandwidth and thus resources? No, as the article points out the median is 8 KB, but the average is 583 KB. The extra 15 KB for each connection would only bump server-side bandwidth serving by ~2%.
But even that is beside my point. The impact of making certificates larger should be, largely, just the cost of making them larger which, on average, would not actually be that significant of a impact. That is not the real problem. The problem is actually that there is so much broken crap everywhere in networks and network stacks that would either break or dramatically balloon what should otherwise be manageable costs.
Everybody just wants to paper over that by blaming the larger certificates when what is actually happening is that the larger certificates are revealing the rot. That is not to say that the proposal which reduces the size of the certificates is bad, I think it is good to do so, but fixing the proximal cause so you can continue to ignore the root cause is a recipe that got us into this ossified, brittle networking mess.
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