Entrust Limited Entrust Limited OpenCA Labs Bundesdruckerei GmbH Cisco Systems This document defines combinations of ML-KEM [FIPS.203] in hybrid with traditional algorithms RSA-OAEP, ECDH, X25519, and X448. These combinations are tailored to meet security best practices and regulatory requirements. Composite ML-KEM is applicable in any application that uses X.509, PKIX, and CMS data structures and protocols that accept ML-KEM, but where the operator wants extra protection against breaks or catastrophic bugs in ML-KEM. For use within CMS, this document is intended to be coupled with the CMS KEMRecipientInfo mechanism in [RFC9629].