Hybrid KEMs combine a post-quantum secure KEM with a traditional
elliptic curve Diffie-Hellman key exchange.
The hybrid construction provides security against both classical and quantum
adversaries: even if one component is broken, the combined scheme remains
secure as long as the other component holds.
The implementation follows the IETF CFRG draft specification for concrete
hybrid KEMs:
https://datatracker.ietf.org/doc/draft-irtf-cfrg-concrete-hybrid-kems/
