It will be interesting to compare PQ rollout to HTTPS rollout historically (either the "SSL becomes widespread in 2015" thing, or the deprecation SSL 3.0). Cloudflare is in an easy position to do stuff like this because it can decouple end user/browser upgrade cycles from backend upgrade cycles.

Some browsers and some end user devices get upgraded quickly, so making it easy to make it optionally-PQ on any site, and then as that rollout extends, some specialty sites can make it mandatory, and then browser/device UX can do soft warnings to users (or other activity like downranking), and then at some point something like STS Strict can be exposed, and then largely become a default (and maybe just remove the non-PQ algorithms entirely from many sites).

I definitely was on team "the risks of a rushed upgrade might outweigh the risks of actual quantum breaks" until pretty recently -- rushing to upgrade has lots of problems always and is a great way to introduce new bugs, but based on the latest information, the balance seems to have shifted to doing an upgrade quickly.

Updating websites is going to be so much easier than dealing with other systems (bitcoin probably the worst; data at rest storage systems; hardware).

• jeroenhd

  today at 4:36 PM

  If any kind of proof about serious quantum computers comes to light, browsers can force most websites' hand by marking non-PQ ciphers as insecure.

  Maybe it'll require TLS 1.4/QUIC 2, with no changes but the cipher specifications, but it can happen in two or three years. Certificates themselves don't last longer than a year anyway. Corporations running ancient software that doesn't support PQ TLS will have the same configuration options to ignore the security warnings already present for TLS 1.0/plain HTTP connections.

  The biggest problem I can imagine is devices talking to the internet no longer receiving firmware updates. If the web host switches protocols, the old clients will start dying off en masses.

  • bwesterb

    today at 4:40 PM

    No need for a TLS 1.4.

    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.

  • PunchyHamster

    today at 6:37 PM

    There is no reason to not support non quantum safe algorithms for foreseeable future in the first place

• bwesterb

  today at 4:33 PM

  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

• stingraycharles

  today at 4:19 PM

  > Updating websites is going to be so much easier than dealing with other systems (bitcoin probably the worst; data at rest storage systems; hardware).

  IPv6 deserves a prominent spot there

Cloudflare pushing PQ by default is probably the single most impactful thing that can happen for adotpion. Most developers will never voluntarily migrate their TLS config. Making it the default at the CDN layer means millions of sites get upgraded without anyone making a decision

• jgrahamc

  today at 4:16 PM

  Cloudflare has long been doing work on PQ (sometimes in conjunction with Google) and rolled out PQ encryption for our customers. You can read about where this all started for us 7 years back: https://blog.cloudflare.com/towards-post-quantum-cryptograph... and four years ago rolled out PQ encryption for all customers: https://blog.cloudflare.com/post-quantum-for-all/

  The big change here is that we're going to roll out PQ authentication as well.

  One important decision was to make this "included at no extra cost" with every plan. The last thing the Internet needs is blood-sucking parasites charging extra for this.

You can do PQ queries with us at qi.rt.ht!

Which one do you think is PQ-secure?

https://qi.rt.ht/?pq={api.,}{stripe,paypal}.com

• 1a527dd5

  today at 4:43 PM

  That is a beautiful api.

> news.ycombinator.com:443 is using X25519, which is not post-quantum secure.

This is the result of Cloudflare's test "Check if a host supports post-quantum TLS key exchange" offered on https://radar.cloudflare.com/post-quantum.

Hoping there is already a migration plan. Fortunately many modern tools make it easy to switch to PQ, maybe someone knows which stack HN is running and if it would be possible.

Along similar lines, Mozilla recently updated their recommended server-side TLS configuration to enable the X25519MLKEM768 post-quantum key exchange now that it's making it into actually-deployed software versions: https://wiki.mozilla.org/Security/Server_Side_TLS At the same time they removed their "old client" compatibility profile as newer TLS libraries do not implement the necessary algorithms (or at least do not enable them by default) and slightly tweaked the "intermediate" compatibility profile to remove a fallback necessary for IE 11 on Windows 7 (now Windows 10 is the minimum compatible version for that profile).

Is this still theory or are there working Quantum systems that have broken anything yet?

• tptacek

  today at 4:48 PM

  Among cryptography engineers there was a sharp vibe shift over the last 2 months; there are papers supporting that vibe shift, but there's also a rumor mill behind it too. The field has basically aligned fully in a way it hadn't before that this is an urgent concern. The simplest way to put it is that everyone's timeline for a real-world CRQC has shortened. Not everyone has the same timeline, but all those timelines are now shorter, and for some important (based on industry and academic position) practitioners, it's down to "imminent".

  • xienze

    today at 6:11 PM

    > The field has basically aligned fully in a way it hadn't before that this is an urgent concern.

    AKA “we want more funding.”

    • dralley

      today at 7:46 PM

      There's a simultaneous push coming from the government to support PQC, ASAP, so it's not just researchers pushing this.

• OkayPhysicist

  today at 4:29 PM

  It's theory. The concern is for avoiding a (likely, IMO) scenario where the only real indication that someone cracked QC is one or more teams of researchers in the field going dark because they got pulled into some tight-lipped NSA project. If we wait until we have an unambiguous path to QC, it might well be too late.

  To avoid the scenario where for a prolonged period of time the intelligence community has secret access to QC, researchers against that type of thing are incentivized to shout fire when they see the glimmerings of a possibly productive path of research.

  • rectang

    today at 6:36 PM

    > one or more teams of researchers in the field going dark

    If the intelligence community is going to nab the first team that has a quantum computing breakthrough, does it actually help the public to speed up research?

    It seems like an arms race the public is destined to lose because the winning team will be subsumed no matter what.

• evil-olive

  today at 5:17 PM

  still theory, but there seems to be an emerging consensus that quantum systems capable of real-world attacks are closer to fruition than most people generally assumed.

  Filippo Valsorda (maintainer of Golang's crypto packages, among other things) published a summary yesterday [0] targeted at relative laypeople, with the same "we need to target 2029" bottom line.

  0: https://words.filippo.io/crqc-timeline/

• PUSH_AX

  today at 4:14 PM

  Nothing has been broken yet, however data can be collected now and be cracked when the time comes, hence why there is a push.

  • thenewnewguy

    today at 6:16 PM

    Can a theoretical strong enough quantum computer break PFS?

    • wahern

      today at 7:01 PM

      QC breaks perfect forward secrecy schemes using non-PQC algorithms, same as for non-PFS. PFS schemes typically use single-use ephemeral DH/ECDH key pairs for symmetric key exchange, separate from the long-term signing keys for authentication.

  • ankit_mishra

    today at 5:17 PM

    [dead]

• moi2388

  today at 3:56 PM

  Theory. And afaik there are still questions as to if the PQ algorithms are actually secure.

  • mswphd

    today at 8:46 PM

    there are no meaningful questions. The only way there are meaningful questions is if you think global cryptographers + governments are part of a cabal to build insecure schemes. The new schemes use

    1. cryptography developed across the world, 2. the actual schemes were overwhelmingly by European authors 3. standardized by the US 4. other countries standardizations have been substantially similar (e.g. the ongoing Korean one, the German BSI's recommendations. China's CACR [had one with substantially similar schemes](https://www.sdxcentral.com/analysis/china-russia-to-adopt-sl...). Note that this is separate from a "standardization", which sounds like it is starting soon).

    In particular, given that China + the US ended up with (essentially the same) underlying math, you'd have to have a very weird hypothetical scenario for the conclusion to not be "these seem secure", and instead "there is a global cabal pushing insecure schemes".

  • tptacek

    today at 5:04 PM

    There are not in fact meaningful questions about whether the settled-on PQC constructions are secure, in the sense of "within the bounds of our current understanding of QC".

    • ls612

      today at 5:09 PM

      Didn't one of the PQC candidates get found to have a fatal classical vulnerability? Are we confident we won't find any future oopsies like that with the current PQC candidates?

      • tptacek

        today at 5:21 PM

        The whole point of the competition is to see if anybody can cryptanalyze the contestants. I think part of what's happening here is that people have put all PQC constructions in bucket, as if they shared an underlying technology or theory, so that a break in one calls all of them into question. That is in fact not at all the case. PQC is not a "kind" of cryptography. It's a functional attribute of many different kinds of cryptography.

        The algorithm everyone tends to be thinking of when they bring this up has literally nothing to do with any cryptography used anywhere ever; it was wildly novel, and it was interesting only because it (1) had really nice ergonomics and (2) failed spectacularly.

      • cwillu

        today at 5:16 PM

        It's the same situation with classical encryption. It's not uncommon for a candidate algorithm [to be discovered ] to be broken during the selection process.

  • sophacles

    today at 4:12 PM

    tbf - since we still don't know if p != np, there are still questions about if the current algorithms are secure also.

    • moi2388

      today at 4:37 PM

      Fair, but recently several PQ algorithms have been shown to in fact not be secure, with known attacks, so I wouldn’t equate them

      • tptacek

        today at 5:04 PM

        Which PQ algorithms would you be referring to here?

        • nick238

          today at 7:19 PM

          https://en.wikipedia.org/wiki/NIST_Post-Quantum_Cryptography... and search for "published attacks".

          • tptacek

            today at 7:43 PM

            Why don't you go ahead and pick out the attacks in here that you think are relevant to this conversation? It can't be on me to do that, because obviously my subtext is that none of them are.

      • sophacles

        today at 4:43 PM

        Interesting. I'd like to learn more about this - where can I find info about it?

        • mswphd

          today at 8:33 PM

          they're almost assuredly talking about two things (maybe 3 if they really know what they're talking about, but the third is something that people making this argument like to pretend doesn't exist).

          1. the main "eye catching" attack was the [attack on SIDH](https://eprint.iacr.org/2022/975.pdf). it was very much a "thought to be entirely secure" to "broken in 5 minutes with a Sage (python variant) implementation" within ~1 week. Degradation from "thought to be (sub-)exp time" to "poly time". very bad.

          2. the other main other "big break" was the [RAINBOW attack](https://eprint.iacr.org/2022/214.pdf). this was a big attack, but it did not break all parameter sets, e.g. it didn't suddenly reduce a problem from exp-time to poly-time. instead, it was a (large) speedup for existing attacks.

          anyway, someone popular among some people in tech (the cryptographer Dan Bernstein) has been trying (successfully) to slow the PQC transition for ~10 years. His strategy throughout has been complaining that a very particular class of scheme ("structured LWE-based schemes") are suspect. He has had several complaints that have shifted throughout the years (galois automorphism structure for a while, then whatever his "spherical models" stuff was lmao). There have been no appreciable better attacks (nothing like the above) on them since then. But he still complains, saying that instead people should use

          1. NTRU, a separate structured lattice scheme (that he coincidentally submitted a scheme for standardization with). Incidentally, it had [a very bad attack](https://eprint.iacr.org/2016/127) ~ 2016. Didn't kill PQC, but killed a broad class of other schemes (NTRU-based fully homomorphic encryption, at least using tensor-based multiplication)

          2. McCliece, a scheme from the late 70s (that has horrendously large public keys --- people avoid it for a reason). He also submitted a version of this for standardization. It also had a [greatly improved attack recently](https://eprint.iacr.org/2024/1193).

          Of course, none of those are relevant to improved attacks on the math behind ML-KEM (algebraically structured variants on ring LWE). there have been some progress on these, but not really. It's really just "shaving bits", e.g. going from 2^140 to 2^135 type things. The rainbow attack (of the first two, the "mild" one) reduced things by a factor ~2^50, which is clearly unacceptable.

          Unfortunately, because adherents of Dan Bernstein will pop up, and start saying a bunch of stuff confidently that is much too annoying to refute, as they have no clue what the actual conversation is. So the conversation becomes

          1. people who know things, who tend to not bother saying anything (with rare exceptions), and 2. people who parrot Dan's (very wrong at this point honestly, but they've shifted over time, so it's more of 'wrong' and 'unwilling to admit it was wrong') opinions.

          the dynamic is similar to how when discussions of vaccines on the internet occur, many medical professionals may not bother engaging, so you'll get a bunch of insane anti-vax conspiracies spread.

Outside of the PQ algorithms not being as thoroughly vetted as others, is there any negatives to shifting algorithms? Like even if someone were to prove that quantum computing is a dud, is there any reason why we shouldn't be using this stuff anyway?

• mswphd

  today at 8:38 PM

  they are much more thoroughly vetted than other schemes. They're more thoroughly vetted than elliptic curves were before we deployed them. Much more vetted than RSA was ever.

  Practically though, there are some downsides. Elliptic curves tend to have smaller ciphertexts/keys/signatures/so are better on bandwidth. If you do everything right with elliptic curves, we're also more confident in the hardness of the underlying problems (cf "generic group lower bounds", and other extensions of this model).

  The new algorithms tend to be easier to implement (important, as a big source of practical insecurity is implementation issues. historically much more than the underlying assumption breaking). This isn't uniformly, e.g. I still think that the FN-DSA algorithm will have issues of this type, but ML-DSA and ML-KEM are fine. They're also easier to "specify", meaning it is much harder to accidentally choose a "weak" instance of them (in several senses. the "weak curve" attacks are not really possible. there isn't really a way to hide a NOBUS backdoor like there was for DUAL_EC_DRBG). They also tend to be faster.

• MrRadar

  today at 7:10 PM

  Post-quantum algorithms tend to be slower than existing elliptic curve algorithms and require more data to be exchanged to provide equivalent security against attacks run on non-quantum computers.

  • tombert

    today at 7:42 PM

    Any idea how much slower? Like are we talking half the speed? A quarter? 1%?

    Sorry, I'm just very out of the loop on some of this stuff and I'm trying to play a game of catchup.

    • MrRadar

      today at 8:05 PM

      This page lists some figures for ML-KEM-768 (which is the PQ key exchange algorithm that's most widely deployed today): https://blog.cloudflare.com/pq-2025/#ml-kem-versus-x25519 This one is actually faster than X25519 (a highly optimized ECC algorithm) by about double but requires 1,184 bytes of data to be exchanged per keyshare vs 32 for X25519. In practice everyone today is using a hybrid algorithm (where you do both ECC and PQ in case the PQ algorithm has an undiscovered weakness) so an ECC+PQ key exchange will be strictly slower than an ECC-only key exchange.

      This page lists some numbers for different PQ signature algorithms: https://blog.cloudflare.com/another-look-at-pq-signatures/#t... Right now the NIST has selected three different ones (ML-DSA, SLH-DSA, and Falcon a.k.a. FN-DSA) which each have different trade-offs.

      SLH-DSA is slow and requires a large amount of data for signatures, however it's considered the most secure of the algorithms (since it's based on the well-understood security properties of symmetric hash algorithms) so it was selected primarily as a "backup" in case the other two algorithms are both broken (which may be possible as they're both based on the same mathematical structure).

      ML-DSA and Falcon are both fairly fast (within an order of magnitude of Ed25519, the X25519 curve signature algorithm), but both require significantly larger keys (41x/28x) and signatures (38x/10x) compared to Ed25519. Falcon has the additional constraint that achieving the listed performance in that table requires a hardware FPU that implements IEEE-754 with constant-time double-precision math. CPUs that do not have such an FPU will need to fall back to software emulation of the required floating point math (most phone, desktop, and server CPUs have such an FPU but many embedded CPUs and microcontrollers do not).

      The net result is that TLS handshakes with PQ signatures and key exchange may balloon to high single- or double-digit kilobytes in size, which will be especially impactful for users on marginal connections (and may break some "middle boxes" https://blog.cloudflare.com/nist-post-quantum-surprise/#dili...).

cloudflare making pq the default is the only way we get real adoption. most devs are never going to mess with their tls settings unless they absolutely have to. having it happen at the cdn level is the perfect silent upgrade for millions of sites without the owners needing to do anything

• diarrhea

  today at 5:21 PM

  https://news.ycombinator.com/item?id=47677483

  • coldpie

    today at 5:31 PM

    I noticed this, too. valeriozen, can you explain what happened here?

    Context, two nearly identical comments from different users.

    hackerman70000 at 16:09 https://news.ycombinator.com/item?id=47677483 :

    > Cloudflare pushing PQ by default is probably the single most impactful thing that can happen for adotpion. Most developers will never voluntarily migrate their TLS config. Making it the default at the CDN layer means millions of sites get upgraded without anyone making a decision

    valeriozen at 16:17 https://news.ycombinator.com/item?id=47677615 :

    > cloudflare making pq the default is the only way we get real adoption. most devs are never going to mess with their tls settings unless they absolutely have to. having it happen at the cdn level is the perfect silent upgrade for millions of sites without the owners needing to do anything

    • wmf

      today at 6:52 PM

      They're using the same AI model?

The CDN part is the easy half. In my work the harder problem has most often been internal service mesh, mTLS between services, any infra that doesn’t terminate at a CDN. Has a bad habit of longer certificate lifetimes and older TLS stacks, and nobody is upgrading it for you.

Quantum computing, and the generic term 'quantum' is gearing up to be the next speculative investment hype bubble after AI, so prepare for a lot of these kinds of articles

• Hasz

  today at 4:15 PM

  nah. governments around the world are hoovering up traffic today with the hope of a "cheap" (by nation state standards) quantum computer. Some of the secrets sent today are "evergreen" (i.e are still relevant 10+ years into the future), amongst a whole lot of cruft. There is massive incentive to hide the technology to keep your peers transmitting in vulnerable encryption as long as possible.

  • nickspacek

    today at 4:31 PM

    For sure, that or just ensuring they have laws in place that grant them access to the unencrypted data we are sending to CDNs operating in their jurisdiction (when necessary for national security reasons).

• bwesterb

  today at 3:51 PM

  At least it's time bound: hope to have this job done by 2029!

[dead]

And that changes what?

• bwesterb

  today at 3:55 PM

  If we do our job, it changes nothing. Problem with security generally: no spectacle if it's all correct. :)

• ljhsiung

  today at 5:55 PM

  "Nothing happened for y2k" energy

• ezfe

  today at 3:44 PM

  It would mean that they're future-proofing their security

The secrecy around this is precisely the opposite of what we saw in the 90s when it started to become clear DES needed to go. Yet another sign that the global powers are preparing for war.

• tptacek

  today at 3:33 PM

  What do you mean? For as long as I remember (back to late 1994) people understood DES to be inadequate; we used DES-EDE and IDEA (and later RC4) instead. What "secrecy" would there have been? The feasibility of breaking DES given a plausible budget goes all the way back to the late 1970s. The first prize given for demonstrating a DES break was only $10,000.

  • adrian_b

    today at 3:56 PM

    Triple-key DES (DES-EDE) had already been proposed by IBM in 1979, in response to the criticism that the 56-bit keys of DES are far too short.

    So practically immediately after DES was standardized, people realized that NSA had crippled it by limiting the key length to 56 bits, and they started to use workarounds.

    Before introducing RC2 and RC4 in 1987, Ronald Rivest had used since 1984 another method of extending the key length of DES, named DESX, which was cheaper than DES-EDE as it used a single block cipher function invocation. However, like also RC4, DESX was kept as a RSA trade secret, until it was leaked, also like RC4, during the mid nineties.

    IDEA (1992, after a preliminary version was published in 1991) was the first block cipher function that was more secure than DES and which was also publicly described.

  • ls612

    today at 5:08 PM

    People were willing to explicitly explain why it was inadequate rather than keep it secret. That is the difference.

    • tptacek

      today at 5:42 PM

      What was to explain? It had a 56-bit key.

      • ls612

        today at 7:26 PM

        Was that the only thing wrong with it? The 90s was definitely before my time but I was under the impression reading about it that there were also fundamental flaws with DES which lead to the competition which ultimately produced AES.

        • tptacek

          today at 7:43 PM

          Yes, that was what was wrong with DES. I mean, it also had an 8-byte block size, which turns out to be inadequate as well, but that's true of IDEA and Blowfish as well.

• NitpickLawyer

  today at 3:15 PM

  My read of the recent google blog post is that they framed it as cryptocurrency related stuff just so they don't say the silent thing out loud. But lots of people "in the know" / working on this are taking it much more seriously than just cryptobros go broke. So my hunch is that there's more to it and they didn't want to say it / couldn't / weren't allowed to.

  • adrian_b

    today at 3:43 PM

    It should be noted that quantum computers are a threat mainly for interactions between unrelated parties which perform legal activities, e.g. online shopping, online banking, notarized legal documents that use long-term digital signatures.

    Quantum computers are not a threat for spies or for communications within private organizations where security is considered very important, where the use of public-key cryptography can easily be completely avoided and authentication and session key exchanges can be handled with pre-shared secret keys used only for that purpose.

  • dadrian

    today at 6:07 PM

    I will bring this up at the next meeting of the secret cryptographer cabal where we decide what information to reveal to non-cryptographers.

  • IncreasePosts

    today at 3:39 PM

    What is "it" that you're referring to?

    • wil421

      today at 3:50 PM

      > mitigating harvest-now/decrypt-later attacks.

      Most likely the NSA or someone else is ahead of the game and already has a quantum computer. If the tech news rumors are to true the NSA has a facility in Utah that can gather large swaths of the internet and process the data.

      • bookofjoe

        today at 5:52 PM

        This?: https://nsa.gov1.info/utah-data-center/

        • tonfa

          today at 6:42 PM

          FYI this is a parody website. (in case it's not obvious)

          • bookofjoe

            today at 8:04 PM

            It wasn't obvious to me!