pq-check.eu_

What this checks

pq-check reports a host’s post-quantum TLS posture in milli-seconds — across both dimensions that matter: key exchange and authentication Most readiness checks stop at key exchange. pq-check measures the whole handshake, so a single scan tells you where an endpoint actually stands on the migration to quantum-safe TLS.

1) Key exchange — confidentiality. Whether the TLS 1.3 handshake negotiates a hybrid ML-KEM group (FIPS 203, such as X25519MLKEM768). This is the control that closes the harvest-now, decrypt-later window, where traffic recorded today is decrypted once a quantum computer exists — the risk that makes this urgent rather than eventual.

2) Authentication — identity & PKI. Whether the server can present a post-quantum certificate — ML-DSA or SLH-DSA (FIPS 204 / 205) — detected by actively offering the post-quantum signature algorithms an ordinary client never sends. This surfaces PQ certificates a normal handshake would never reveal, so you can see whether the identity layer is on its migration path too, not only the key exchange.

Covering both key exchange and authentication in one fast, non-intrusive scan — no agent, nothing sent to the target beyond the handshake itself — is what makes the result actionable: not just “are today’s sessions protected,” but “is the full TLS stack, confidentiality and identity alike, moving to post-quantum.” It is the combination, delivered fast, that sets pq-check apart.

Harvest now, decrypt later

An attacker can record encrypted traffic today and decrypt it years from now, once a large enough quantum computer exists. Anything that must stay confidential beyond the next decade is already at risk. Post-quantum key exchange closes that window — which is why it matters that your servers turn it on now, not after quantum computers arrive.

How it works

Enter a hostname and pq-check opens a standard TLS 1.3 handshake to port 443 or 8443, reads the key-exchange groups, TLS version and certificate the server offers, and reports whether a hybrid post-quantum group was negotiated. It performs no exploitation and does not alter the target in any way — see acceptable use.

The methodology page documents the exact groups probed, the pass/fail rules, the footprint left on a scanned host, what is stored, and how to reproduce any result yourself with openssl s_client.