The state of post-quantum readiness on the web

Methodology

Once a day we open two or three read-only TLS connections to each host in a fixed public panel. The first sends nothing at all, and records whether the server selects the hybrid group X25519MLKEM768, the negotiated TLS version, the leaf certificate’s signature algorithm and expiry, and whether it volunteers a session ticket. Hosts that volunteer none get a second connection carrying a single HEAD /, because many servers withhold a ticket until a request arrives. The last connection offers that ticket back, to the same address and the same server name that issued it, and records whether the server resumes. We send no credentials, we never offer a ticket to a host that did not issue it, we honor connection refusals, and we do not attempt any exploitation. This is the same class of measurement public scanners such as SSL Labs and Censys perform.

The panel and the probing policy live in the open-source pqc-observatory repository, where anyone can propose a host. To have a host removed from the panel, open a pull request or contact [email protected] and we will drop it within one measurement cycle.

Full methodology, and what this number is not →