This is a good take, there's really not much to argue about.
>[...] the availability of HPKE hybrid recipients, which blocked on the CFRG, which took almost two years to select a stable label string for X-Wing (January 2024) with ML-KEM (August 2024), despite making precisely no changes to the designs. The IETF should have an internal post-mortem on this, but I doubt we’ll see one
My kingdom for a standards body that discusses and resolves process issues.
It should be noted that if indeed there has not remained much time until a usable quantum computer will become available, the priority is the deployment of FIPS 203 (ML-KEM) for the establishment of the secret session keys that are used in protocols like TLS or SSH.
ML-KEM is intended to replace the traditional and the elliptic-curve variant of the Diffie-Hellman algorithm for creating a shared secret value.
When FIPS 203, i.e. ML-KEM is not used, adversaries may record data transferred over the Internet and they might become able to decrypt the data after some years.
On the other hand, there is much less urgency to replace the certificates and the digital signature methods that are used today, because in most cases it would not matter if someone would become able to forge them in the future, because they cannot go in the past to use that for authentication.
The only exception is when there would exist some digital documents that would completely replace some traditional paper documents that have legal significance, like some documents proving ownership of something, which would be digitally signed, so forging them in the future could be useful for somebody, in which case a future-proof signing method would make sense for them.
OpenSSH, OpenSSL and many other cryptographic libraries and applications already support FIPS 203 (ML-KEM), so it could be easily deployed, at least for private servers and clients, without also replacing the existing methods used for authentication, e.g. certificates, where using post-quantum signing methods would add a lot of overhead, due to much bigger certificates.
That was my position until last year, and pretty much a consensus in the industry.
What changed is that the new timeline might be so tight that (accounting for specification, rollout, and rotation time) the time to switch authentication has also come.
ML-KEM deployment is tangentially touched on in the article because it's both uncontroversial and underway, but:
> This is not the article I wanted to write. I’ve had a pending draft for months now explaining we should ship PQ key exchange now, but take the time we still have to adapt protocols to larger signatures, because they were all designed with the assumption that signatures are cheap. That other article is now wrong, alas: we don’t have the time if we need to be finished by 2029 instead of 2035.
> For key exchange, the migration to ML-KEM is going well enough but: 1. Any non-PQ key exchange should now be considered a potential active compromise, worthy of warning the user like OpenSSH does, because it’s very hard to make sure all secrets transmitted over the connection or encrypted in the file have a shorter shelf life than three years. [...]
You comment is essentially the premise of the other article.
I agree with you that one must prepare for the transition to post-quantum signatures, so that when it becomes necessary the transition can be done immediately.
However that does not mean that the switch should really be done as soon as it is possible, because it would add unnecessary overhead.
This could be done by distributing a set of post-quantum certificates, while continuing to allow the use of the existing certificates. When necessary, the classic certificates could be revoked immediately.
> The only exception is when there would exist some digital documents that would completely replace some traditional paper documents that have legal significance, like some documents proving ownership of something, which would be digitally signed, so forging them in the future could be useful for somebody, in which case a future-proof signing method would make sense for them.
This very much exists. In particular, the cryptographic timestamps that are supposed to protect against future tampering are themselves currently using RSA or EC.
Building out a supercomputer capable of breaking cryptography is exactly the kind of thing I expect governments to be working on now. It is referenced in the article, but the analogy to the Manhattan Project is clear.
Prior to 1940 it was known that clumping enough fissile material together could produce an explosion. There were engineering questions around how to purify uranium and how to actually construct the weapon etc. But the phenomenon was known.
I say this because there’s a meme that governments are cooking up exotic technologies behind closed doors which I personally tend to doubt.
This is almost perfect analogy to the MP though. We know exactly what could happen if we clumped enough qubits together. There are hard engineering challenges of actually doing so, and governments are pretty good at clumping dollars together when they want to.
The Manhattan project employed some significant % of all of America. A project of that scale will likely never happen again.
It was also about far more than the science. It was about industrializing the entire production process and creating industrial capability that simply did not exist before.
What is the consequence on e.g. Yubikeys (or say the Android Keystore)? Do I understand correctly that those count as "signature algorithms" and are a little less at risk than "full TEEs" because there is no "store now, decrypt later" for authentication?
E.g. can I use my Yubikey with FIDO2 for SSH together with a PQ encryption, such that I am safe from "store now, decrypt later", but can still use my Yubikey (or Android Keystore, for that matter)?
This article is more aimed at those specifying and implementing WebAuthN and SSH, than at those using them.
They/we need to migrate those protocols to PQ now, so that you all can start migrating to PQ keys in time, including the long tail of users that will not rotate their keys and hardware the moment the new algorithms are supported.
For example, it might be too late to get anything into Debian for it to be in oldstable when the CRQCs come!
If you are doing a post-quantum key exchange and only authenticating with the Yubikey, then you are safe from after-the-fact attacks. Well, as long as the PQ key exchange holds up, and I am personally not as optimistic about that as I’d like to be.
I was in this field a while back, and I always found it baffling that anyone ever believed in the earlier large estimates for the size of a quantum computer needed to run Shor's algorithm. For a working quantum computer, Shor's algorithm is about as difficult as modular exponentiation or elliptic curve scalar multiplication, it can compute discrete logs. To break keys of a few hundred bits, you need a few hundred qubits plus not all that much overhead. And the error correction keeps improving all the time.
Also...
> Trusted Execution Environments (TEEs) like Intel SGX and AMD SEV-SNP and in general hardware attestation are just f**d. All their keys and roots are not PQ and I heard of no progress in rolling out PQ ones, which at hardware speeds means we are forced to accept they might not make it, and can’t be relied upon.
This part is embarrassing. We’ve had hash-based signatures that are plenty good for this for years and inspire more confidence for long-term security than the lattice schemes. Sure, the private keys are bigger. So what?
We will also need some clean way to upgrade WebAuthn keys, and WebAuthn key management currently massively sucks.
In rebuttal, Peter Gutmann seems to think the progress towards quantum computing devices which can break commonly used public key crypto systems is not moving especially quickly: https://eprint.iacr.org/2025/1237
What do you recomend as reading material for someone that was in college a while ago (before AE modes got popular) to get up to speed with the new PQ developments?
If you want something book-shaped, the 2nd edition of Serious Cryptography is updated to when the NIST standards were near-final drafts, and has a nice chapter on post-quantum cryptography.
If you want something that includes details on how they were deployed, I'm afraid that's all very recent and I don't have good references.
This seems like something uniquely suited to the startup ecosystem. I.e. offering PQ Encryption Migration as a Service. PQ algorithms exist and now theres a large lift required to get them into the tech with substantial possible value.
… really? This is simultaneously so far down in the plumbing and extremely resistant to measuring the impact of, I can’t imagine anyone building a company off of this that’s not already deep in the weeds (lookin’ at you, WolfSSL).
The idea that a startup would be competitive in the VC “the only thing that matters are the feels” environment seems crazy to me.
Yeah... I spent the 90s working for RSADSI and Certicom implementing algorithms. Crypto is a vitamin, not an aspirin. Hardly anyone is capable of properly assessing risk in general, much less the technical world of information risk management. Telling someone they should pay you money to reduce the impact of something that may or may not happen in the future is not a sales win.
So... In 2013 I was working for Mozilla adding TLS 1.1 and 1.2 support into Firefox. It turns out that some of the extensions common in 1.1, in some instances caused PDUs to grow beyond 16k (or maybe it was 32k, can't remember.). This caused middle boxes to barf. Sure, they shouldn't barf, but they did. We discovered the problem (or rather one of our users discovered the problem) by increasing the key size on server and client certs to push PDU sizes over the limit.
At the very least, you want to start using hybrid legacy / pqc algorithms so engineers at Cisco will know not to limit key sizes in PDUs to 128 bytes.
A few points here:
There is already very wide use of PQ algorithms in the Web context [0], which is the most problematic one because clients need to be able to connect to any site and there's no real coordination between sites and clients. So we're exercising the middleboxes already.
The incident you're thinking of doesn't sound familiar. None of the extensions in 1.1 really were that big, though of course certs can get that big if you work hard enough. Are you perhaps thinking instead of the 256-511 byte ClientHello issue addressed ion [1]
This is a good take, there's really not much to argue about.
>[...] the availability of HPKE hybrid recipients, which blocked on the CFRG, which took almost two years to select a stable label string for X-Wing (January 2024) with ML-KEM (August 2024), despite making precisely no changes to the designs. The IETF should have an internal post-mortem on this, but I doubt we’ll see one
My kingdom for a standards body that discusses and resolves process issues.
I missed you at the most recent CRFG meeting.
It should be noted that if indeed there has not remained much time until a usable quantum computer will become available, the priority is the deployment of FIPS 203 (ML-KEM) for the establishment of the secret session keys that are used in protocols like TLS or SSH.
ML-KEM is intended to replace the traditional and the elliptic-curve variant of the Diffie-Hellman algorithm for creating a shared secret value.
When FIPS 203, i.e. ML-KEM is not used, adversaries may record data transferred over the Internet and they might become able to decrypt the data after some years.
On the other hand, there is much less urgency to replace the certificates and the digital signature methods that are used today, because in most cases it would not matter if someone would become able to forge them in the future, because they cannot go in the past to use that for authentication.
The only exception is when there would exist some digital documents that would completely replace some traditional paper documents that have legal significance, like some documents proving ownership of something, which would be digitally signed, so forging them in the future could be useful for somebody, in which case a future-proof signing method would make sense for them.
OpenSSH, OpenSSL and many other cryptographic libraries and applications already support FIPS 203 (ML-KEM), so it could be easily deployed, at least for private servers and clients, without also replacing the existing methods used for authentication, e.g. certificates, where using post-quantum signing methods would add a lot of overhead, due to much bigger certificates.
That was my position until last year, and pretty much a consensus in the industry.
What changed is that the new timeline might be so tight that (accounting for specification, rollout, and rotation time) the time to switch authentication has also come.
ML-KEM deployment is tangentially touched on in the article because it's both uncontroversial and underway, but:
> This is not the article I wanted to write. I’ve had a pending draft for months now explaining we should ship PQ key exchange now, but take the time we still have to adapt protocols to larger signatures, because they were all designed with the assumption that signatures are cheap. That other article is now wrong, alas: we don’t have the time if we need to be finished by 2029 instead of 2035.
> For key exchange, the migration to ML-KEM is going well enough but: 1. Any non-PQ key exchange should now be considered a potential active compromise, worthy of warning the user like OpenSSH does, because it’s very hard to make sure all secrets transmitted over the connection or encrypted in the file have a shorter shelf life than three years. [...]
You comment is essentially the premise of the other article.
I agree with you that one must prepare for the transition to post-quantum signatures, so that when it becomes necessary the transition can be done immediately.
However that does not mean that the switch should really be done as soon as it is possible, because it would add unnecessary overhead.
This could be done by distributing a set of post-quantum certificates, while continuing to allow the use of the existing certificates. When necessary, the classic certificates could be revoked immediately.
How do you do revocation or software updates securely if your current signature algorithm is compromised?
> The only exception is when there would exist some digital documents that would completely replace some traditional paper documents that have legal significance, like some documents proving ownership of something, which would be digitally signed, so forging them in the future could be useful for somebody, in which case a future-proof signing method would make sense for them.
This very much exists. In particular, the cryptographic timestamps that are supposed to protect against future tampering are themselves currently using RSA or EC.
Building out a supercomputer capable of breaking cryptography is exactly the kind of thing I expect governments to be working on now. It is referenced in the article, but the analogy to the Manhattan Project is clear.
Prior to 1940 it was known that clumping enough fissile material together could produce an explosion. There were engineering questions around how to purify uranium and how to actually construct the weapon etc. But the phenomenon was known.
I say this because there’s a meme that governments are cooking up exotic technologies behind closed doors which I personally tend to doubt.
This is almost perfect analogy to the MP though. We know exactly what could happen if we clumped enough qubits together. There are hard engineering challenges of actually doing so, and governments are pretty good at clumping dollars together when they want to.
The Manhattan project employed some significant % of all of America. A project of that scale will likely never happen again.
It was also about far more than the science. It was about industrializing the entire production process and creating industrial capability that simply did not exist before.
What is the consequence on e.g. Yubikeys (or say the Android Keystore)? Do I understand correctly that those count as "signature algorithms" and are a little less at risk than "full TEEs" because there is no "store now, decrypt later" for authentication?
E.g. can I use my Yubikey with FIDO2 for SSH together with a PQ encryption, such that I am safe from "store now, decrypt later", but can still use my Yubikey (or Android Keystore, for that matter)?
This article is more aimed at those specifying and implementing WebAuthN and SSH, than at those using them.
They/we need to migrate those protocols to PQ now, so that you all can start migrating to PQ keys in time, including the long tail of users that will not rotate their keys and hardware the moment the new algorithms are supported.
For example, it might be too late to get anything into Debian for it to be in oldstable when the CRQCs come!
Your Yubikey itself is doomed.
If you are doing a post-quantum key exchange and only authenticating with the Yubikey, then you are safe from after-the-fact attacks. Well, as long as the PQ key exchange holds up, and I am personally not as optimistic about that as I’d like to be.
I was in this field a while back, and I always found it baffling that anyone ever believed in the earlier large estimates for the size of a quantum computer needed to run Shor's algorithm. For a working quantum computer, Shor's algorithm is about as difficult as modular exponentiation or elliptic curve scalar multiplication, it can compute discrete logs. To break keys of a few hundred bits, you need a few hundred qubits plus not all that much overhead. And the error correction keeps improving all the time.
Also...
> Trusted Execution Environments (TEEs) like Intel SGX and AMD SEV-SNP and in general hardware attestation are just f**d. All their keys and roots are not PQ and I heard of no progress in rolling out PQ ones, which at hardware speeds means we are forced to accept they might not make it, and can’t be relied upon.
This part is embarrassing. We’ve had hash-based signatures that are plenty good for this for years and inspire more confidence for long-term security than the lattice schemes. Sure, the private keys are bigger. So what?
We will also need some clean way to upgrade WebAuthn keys, and WebAuthn key management currently massively sucks.
In rebuttal, Peter Gutmann seems to think the progress towards quantum computing devices which can break commonly used public key crypto systems is not moving especially quickly: https://eprint.iacr.org/2025/1237
That's not a rebuttal. The post references the paper and a rebuttal to it from an expert in the field.
Damn. It's like I insulted Vault.
Also, I went over Filippo's post again and still can't see where it references the Gutmann / Neuhaus paper. Are we talking about the same post?
From Filippo's post: "Sure, papers about an abacus and a dog are funny and can make you look smart and contrarian on forums."
What do you recomend as reading material for someone that was in college a while ago (before AE modes got popular) to get up to speed with the new PQ developments?
If you want something book-shaped, the 2nd edition of Serious Cryptography is updated to when the NIST standards were near-final drafts, and has a nice chapter on post-quantum cryptography.
If you want something that includes details on how they were deployed, I'm afraid that's all very recent and I don't have good references.
There is always a price to encryption. The cost goes up the more you have to cater to different and older encryptions while supporting the latest.
This seems like something uniquely suited to the startup ecosystem. I.e. offering PQ Encryption Migration as a Service. PQ algorithms exist and now theres a large lift required to get them into the tech with substantial possible value.
… really? This is simultaneously so far down in the plumbing and extremely resistant to measuring the impact of, I can’t imagine anyone building a company off of this that’s not already deep in the weeds (lookin’ at you, WolfSSL).
The idea that a startup would be competitive in the VC “the only thing that matters are the feels” environment seems crazy to me.
Yeah... I spent the 90s working for RSADSI and Certicom implementing algorithms. Crypto is a vitamin, not an aspirin. Hardly anyone is capable of properly assessing risk in general, much less the technical world of information risk management. Telling someone they should pay you money to reduce the impact of something that may or may not happen in the future is not a sales win.
Why do we "need to ship"? 1,000 qubit quantum computers are still decades away at this point
So... In 2013 I was working for Mozilla adding TLS 1.1 and 1.2 support into Firefox. It turns out that some of the extensions common in 1.1, in some instances caused PDUs to grow beyond 16k (or maybe it was 32k, can't remember.). This caused middle boxes to barf. Sure, they shouldn't barf, but they did. We discovered the problem (or rather one of our users discovered the problem) by increasing the key size on server and client certs to push PDU sizes over the limit.
At the very least, you want to start using hybrid legacy / pqc algorithms so engineers at Cisco will know not to limit key sizes in PDUs to 128 bytes.
A few points here: There is already very wide use of PQ algorithms in the Web context [0], which is the most problematic one because clients need to be able to connect to any site and there's no real coordination between sites and clients. So we're exercising the middleboxes already.
The incident you're thinking of doesn't sound familiar. None of the extensions in 1.1 really were that big, though of course certs can get that big if you work hard enough. Are you perhaps thinking instead of the 256-511 byte ClientHello issue addressed ion [1]
[0] https://blog.cloudflare.com/pq-2025/ [1] https://datatracker.ietf.org/doc/html/rfc7685
Yes, this is why I invested in QRL crypto. With lates updates and no T1 exchange it looks like a good opportunity to grow.