Handled it: decompressed and parsed the 2-certificate, 15,430-byte ML-DSA-87 chain, then rejected it on trust (alert 42). That is the right answer to a private CA, and reaching it means the certificate message itself was handled.
The client did what the clause requires.
What was measured
- Client
- quico — quico + lemon-tls, 0.7.0 (npm)
- Test
- Post-quantum certificate chain, compressed per RFC 8879 —
t-cert-compression-pq - Clause
- RFC 8879 §4, RFC 8446 §4.4.2 (MAY)
- Class
- discretionary — The RFC permits either behaviour; the report says which was chosen.
- Required behaviour
- Decompress and parse an ML-DSA-87 chain, then judge it on its merits. Nothing here is graded: RFC 8879 is optional, no RFC requires support for ML-DSA certificates, and §4 expressly lets a receiver cap the decompressed size and abort. What the port reports is which of those a client does. The chain is deliberately issued by a private CA nobody trusts, and that is what makes the measurement work rather than spoiling it. A client that rejects it for its *trust anchor* — unknown_ca, or bad_certificate — has already decompressed a certificate message several times the size of a classical one, parsed ML-DSA-87 structures it may never have seen and got as far as chain building. That is the whole capability under test, and the rejection that follows is correct behaviour, not a failure. A client that cannot get that far answers differently: decode_error or a record-size abort says the compressed chain itself defeated it, which is the outcome the post-quantum migration needs to know about. Certificate sizes are the half of that migration nobody can configure their way out of — ML-DSA-87 signatures are 4,627 bytes each and every chain carries several.
- Measured
- 2026-10-15
Reproduce it
The suite is the judge, so the reproduction is to point the same client at the same test and let the server report what it saw.
SESSION=$(curl -sX POST https://conformance.pqcrypta.com/session | jq -r .id)
# then drive quico at the test URL and read the verdict:
curl -s https://conformance.pqcrypta.com/report/$SESSION.json | jq '.results["t-cert-compression-pq"]'