Participant Relationship Protocol

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K01-MQ: Yes

Rationale

The previously unselected TLS group now has a pinned hybrid configuration and an executed witness. A local static OpenSSL 3.5.0 build provides X25519MLKEM768 to the pinned Picotls and picoquic sources. With the client restricted through picoquic_set_key_exchange to group 4588, the server completed the hybrid exchange and produced a 64-byte combined secret. The native QUIC simulator then delivered 256 useful bytes in each direction through the existing test callbacks. Picotls passes the combined KEM secret into its TLS 1.3 key schedule. OpenSSL mlx_kem.c places the ML-KEM and ECDH secrets in separate portions of the combined buffer and checks their lengths. This supports the bounded passive recorded-traffic confidentiality claim for the selected hybrid construction, under its cryptographic assumptions.

Assessment method

Explicit hybrid configuration, isolated provider build, native simulator positive/negative controls

Source context

Pinned official picoquic/Picotls/OpenSSL sources and local three-case execution, 2026-10-22

Outstanding qualification

Default preferences are not a fail-closed PQ policy: a default client successfully exchanged the same data with a classical-only server using X25519 (29). The client restricted to group 4588 was instead rejected by that server with TLS handshake_failure (QUIC error 0x128), without reaching ready. The test changes make unsupported algorithms fail rather than silently skip, add group/secret-length observation, and add data and negative controls; they do not change the cryptographic implementation. The first negative assertion incorrectly expected a nonzero simulator-loop return; it was corrected to inspect the actual TLS error and connection state, retaining the original log. This is native code execution over simulated packet delivery, not two independent implementations, a live multipath run or a public deployment. Test certificate/SNI settings are the upstream fixture, not a revalidation of the column's complete mutual-authentication/no-SNI configuration. No PQ certificate authentication, security audit, throughput result or extension of earlier byte-budget witnesses is claimed. OpenSSL 3.5.0 is an isolated reproducibility pin, not a deployment recommendation.

Public sources

Editorial evidence references

The following identifiers refer to research records not included in this public package; they are not public links.