Core engineering and protocols for RFC 9180 Hybrid HPKE.
RFC 9180 defines Hybrid Public Key Encryption (HPKE), the modern standard for asynchronous encryption used in Privacy-Preserving Measurement (PPM), MLS, and encrypted DNS. MLKEMSecure extends HPKE with composite KEM identifiers, allowing applications to encrypt payloads to recipient public keys without establishing an interactive session.
The HPKE key schedule incorporates application-specific context strings (info parameters), recipient public key fingerprints, and ephemeral public keys into the HKDF-Extract step. This cryptographic binding mathematically prevents cross-protocol attacks and cipher-suite substitution attacks across enterprise microservices.