Post Syndicated from Andrew Depke original https://blog.cloudflare.com/post-quantum-visibility/
Today, we are introducing additional post-quantum (PQ) cryptography visibility tools into Cloudflare's Application Security and Logs products. You can now inspect and graph the adoption of post-quantum TLS 1.3 encryption for live traffic from directly within Logpush, Log Explorer, and the HTTP Traffic Analytics dashboard. By surfacing the key exchange algorithm negotiated on every incoming request from visitors to our platform, Cloudflare gives customers granular, per-connection telemetry to audit their post-quantum posture, assess compliance, and identify cryptographic gaps across their domains.
Cloudflare is targeting 2029 for full post-quantum security, and executing a cryptographic transition at scale requires detailed telemetry. We’ve already deployed post-quantum encryption across many of our products, including in our cloud-proxy platform and on every on-ramp and off-ramp of our SASE platform. As many of our customers work towards quantum-readiness deadlines around 2030, we’re helping ease the transition by making post-quantum encryption the default in many of our products, sharing learnings from our internal cryptography discovery tool, and launching the new post-quantum visibility features for TLS that we’ll cover in this blog.
Bringing post-quantum visibility to the domain level
When it comes to post-quantum visibility, we already have macro-level visibility into Internet-wide post-quantum adoption in TLS through Cloudflare Radar. On Radar, we track global post-quantum encryption statistics, both when Cloudflare proxies HTTP requests from visitors (the visitor-to-Cloudflare connection) and when Cloudflare connects to origin servers (the Cloudflare-to-origin connections), as shown in this figure.
From Radar we can see that about 70% of browser-generated traffic hitting Cloudflare's network (on the visitor-to-Cloudflare connection) is protected with post-quantum encryption using hybrid ML-KEM (FIPS 203). Meanwhile, we can see that today, just about 15% of origins that Cloudflare connects to use hybrid ML-KEM. These are aggregate numbers; the first number is aggregated across all the browser-generated traffic we see, and the second number is aggregated across all the origins we connect to.
We’ve also recently launched Automatic Key Exchange for the Cloudflare-to-origin connection, which reveals which cryptographic algorithms are supported by a given origin. This is useful because outdated configurations can cause an origin to connect to Cloudflare using classical cryptography, even if it does support a post-quantum encryption.
While Radar and Automatic Key Exchange both provide valuable macro-level views of Internet-wide readiness, our customers have asked us to be able to go beyond aggregate numbers and dive into the behavior of individual domains.
We have long provided visibility into the TLS version used at individual domains (TLS 1.3, TLS 1.2, etc.).
But until now we have not exposed information about the cryptographic algorithms used with the TLS version used at the domain level. This means customers could not answer questions like “What fraction of traffic to my domain www.example.com is using post-quantum encryption?” This information is helpful when aiming to comply with regulatory frameworks, troubleshooting a migration to post-quantum encryption, or seeking to understand which fraction of traffic that is exposed to future quantum adversaries. Now, these questions can be answered.
Post-quantum cryptography in TLS
Before we get into the new product features, let’s do a quick review of post-quantum cryptography in TLS, so we can understand the information that the feature surfaces.
In 2024, the National Institute of Standards and Technology (NIST) stated that RSA and Elliptic Curve Cryptography (ECC) should be deprecated by 2030, and many governments and regulators have since gotten behind that deadline. That’s why today, many of our products are protected with post-quantum encryption using a cryptographic key agreement algorithm called hybrid ML-KEM. Post-quantum encryption is needed right now to stop harvest-now-decrypt-later attacks, where an adversary harvests data today and then decrypts it in the future once powerful quantum computers come online. Organizations that have data that are valuable even if decrypted in 3–10 years (public sector, defense, finance, telecom, healthcare, and others), should consider immediately protecting their traffic with post-quantum encryption.
In TLS 1.3, the key exchange group X25519MLKEM768 is the only recommended algorithm for post-quantum encryption. It is now the algorithm preferred by most major browsers. (Note: post-quantum encryption is not available in TLS 1.2 or any earlier version of TLS.) If you are using Chrome, you can check the key agreement algorithm used by this webpage (or any other) by right-clicking “Inspect”, going to the “Security” tab and looking for the below:
With X25519MLKEM768 in TLS 1.3, the client and server execute both:
- the Elliptic Curve Diffie-Hellman Key Exchange (ECDHE) over curve X25519 and
- the post-quantum Module Lattice Key Encapsulation Mechanism (ML-KEM)
X25519 and MLKEM768 each produce a shared secret. TLS then combines those two secrets and uses the result to encrypt TLS traffic. This hybrid approach provides belt-and-suspenders security; as long as one of the two key exchanges is secure, the resulting shared secret is also secure. TLS 1.3 also supports other key exchange groups, including X25519, P-256 and P-384, all of which are just classical ECDHE over different elliptic curves; these algorithms are still used all over the web. In earlier versions of TLS you can also find key agreement based on the RSA algorithm, which is quantum-vulnerable and thankfully much less popular these days due to many known classical security problems.
But post-quantum encryption is only the first part of the story; the second part is post-quantum authentication. Once powerful quantum computers exist, we need to worry about upgrading the certificates and signatures used in TLS 1.3 away from RSA and ECC and towards post-quantum algorithms like ML-DSA. We’re actively making progress towards that goal. In fact, we recently announced that origins can use ML-DSA-44 certificates over TLS 1.3 to connect to Cloudflare, and today we announced that we’re launching a certificate authority that will support post-quantum Merkle Tree Certificates. Nevertheless, for now it remains true that post-quantum encryption with hybrid MLKEM is more broadly deployed than post-quantum authentication.
Bringing post-quantum visibility to the visitor-to-Cloudflare connection
Today we’re making it possible to see the extent to which post-quantum key agreement is used on the visitor-to-Cloudflare connection for any domain in HTTP Traffic Analytics dashboard, Logpush, and Log Explorer.
To view the TLS key exchange data on your domains, go to the Cloudflare Dashboard, and navigate to HTTP Traffic under the Analytics tab. Here you’ll get in-depth statistics about the kinds of traffic visiting your domains, now including a dedicated card for TLS Key Exchange groups on the visitor-to-Cloudflare connection. (Scroll down to find it!) Here’s a look at a TLS Key Exchange card for one of our test domains:
As you can see, the majority of the traffic to this domain uses post-quantum X25519MLKEM768 (in TLS 1.3). We see some traffic using classical ECDHE over curve X25519 or P-256 (in TLS 1.3 or below). The traffic labeled “None” is using either RSA key agreement (in TLS 1.2 or below) or no TLS at all. And finally we have a small number of visitors using the now-deprecated X25519Kyber768Draft00 algorithm with TLS 1.3, which we implemented back before X25519MLKEM768 was fully standardized by the Internet Engineering Task Force (IETF). We’ve waited to remove support for X25519Kyber768Draft00 until observed connections are diminishingly small, to avoid regressing clients for which this is their only way to support PQ encryption.
While we’re here, we’ll just drop a few tips about PQ-ing your traffic. If you look at your domain and find no use of X25519MLKEM768 at all, you should confirm that TLS 1.3 is enabled. In the Cloudflare dashboard, select your domain, go to SSL/TLS > Edge Certificates, and then scroll until you find the TLS 1.3 switch; switch TLS 1.3 to On. (There is no separate post-quantum setting: when TLS 1.3 is enabled and a visitor supports X25519MLKEM768, Cloudflare negotiates it automatically.) Also, if the vast majority of your traffic is over classical X25519, P-256, P-384, or None, it might be because most visitors to that domain are non-browser clients that lack support for X25519MLKEM768 and/or TLS 1.3. (Again, most major browsers do prefer to negotiate a TLS 1.3 connection with X25519MLKEM768.)
The key exchange group can now also be a filtering term in the HTTP Traffic dash. Here’s how to take a look at the traffic that is not using post-quantum encryption with X25519MLKEM768:
Analytics are great for aggregate investigations, but being able to see this information in individual log lines can be even more powerful. You can enable the new ClientTLSKeyExchangeGroup field, under the TLS category in the HTTP Requests dataset, to gain visibility into individual post-quantum key exchange in your Log Explorer and Logpush connection logs.
With this new field enabled, you’ll see it start appearing in your Logpush HTTP Request logs, like so:
Visibility to origins and more
The release of the key exchange group stats represents the first major milestone in our broader cryptographic visibility initiative. Designed for scalability, our underlying telemetry pipeline is built to ingest additional cryptographic parameters from TLS handshakes.
That’s why we’ve also surfaced the key exchange group from the Cloudflare-to-origin connection and to provide end-to-end visibility from eyeball to origin in Logpush as OriginTLSKeyExchangeGroup. (This group will be the same for all visitor connections made to that domain, which is why it's not shown in the HTTP Traffic Analytics dashboard).
And for customers that use legacy origin servers that are unlikely to support modern post-quantum cryptography, don’t despair. You can put the origin server behind a Cloudflare Tunnel, to tunnel traffic from the origin server to Cloudflare over TLS 1.3 with X25519MLKEM768, without need to upgrade the legacy origin server itself. This is what the network configuration would look like if you put your origin server behind a Cloudflare Tunnel:
Eventually we’ll be able to also surface post-quantum authentication (namely the algorithm used for certificates and signatures in TLS, including Merkle Tree Certificates) once we start to see a broader-based deployment of that technology.
Your domain has started its post-quantum journey
If your domain is behind Cloudflare, its post-quantum journey is already underway. Check HTTP Traffic Analytics dash and your logs to see the percentage of visitor connections to your domain that already use TLS 1.3 with post-quantum encryption (X25519MLKEM768). You can also check logs to see if you’re using post-quantum encryption on the Cloudflare-to-origin connection. If your origin server is too ossified to support post-quantum cryptography, then just put it behind Cloudflare Tunnel. With the right settings and visibility, you can protect more of your traffic on Cloudflare from harvest-now-decrypt-later attacks today.
We thank Luke Valenta, Ollie Hsieh and Alex Krivit for contributions to this work.