transport · severity medium
Post-quantum key exchange
Share of TLS 1.3 endpoints still negotiating a classical key exchange, with no post-quantum protection against traffic captured now and decrypted later.
Measured every Wednesday · last updated
How it is measured
Tier 2. One TLS handshake offering X25519MLKEM768 ahead of the classical curves, then read which group the server actually chose. TLS 1.2 endpoints are excluded, not counted as classical — they have no post-quantum key exchange to decline, and "not on TLS 1.3" is already tls-legacy against a different denominator. Denominator: has_web.
Why it matters
The failure with no symptom at all. The padlock is green, the grade is an A, the protocol is current, and the key exchange is the one part that does not survive contact with a quantum computer — retrospectively, because traffic captured today can be decrypted years later once the capability exists. Nothing about the site will ever look wrong, and by the time it matters the recording has already been made. The 47-day certificate clock has a deadline; this one has a countdown nobody can see.
Limits of this measurement
Measures the key exchange only — a hybrid group protects the session key, not the certificate's signature, so hybrid_pq is not "quantum-safe" end to end and must not be reported as such. Server support is read as offered to our client: a server may prefer a PQ group with a browser that offers a different one. The rate reflects hosting and CDN defaults far more than any decision made by the domain's owner, which is much of the story. Capped at 2,000 domains per run because it needs its own handshake rather than sharing the one the certificate metrics already make.
The base rate
Two independent populations. The global, domain-anchored figure is unbiased; the company-anchored figures are built by matching company names to domains and skew toward more digitally-mature firms. Both are published, so the gap is visible.
By company size band
Company-anchored cuts (national registries with a size proxy), split by size band. Right-hand figure is the share not meeting the control.
Every segment
Pick one to see the citable answer for a company like yours, with its trend and methodology.
Show the remaining 4 segments
Slices below 100 measured members are withheld rather than shown with a wide interval — an absent country or issuer means too little data, not zero failures. Licensed CC BY 4.0. Machine-readable data per segment: append .json or .csv to its URL.