Post-quantum cryptography
Key encapsulation mechanism
KEM
A construction for securely establishing a shared symmetric key: the sender encapsulates a random secret under the recipient's public key, and the recipient decapsulates it with their private key. Both then hold the same secret.
In practice
ML-KEM is a KEM; ECDH is a key-agreement scheme used for the same purpose.
Related terms
ML-KEM
The NIST-standardised post-quantum key encapsulation mechanism, used to establish a shared secret over an untrusted network. It is the replacement for RSA key transport and elliptic-curve Diffie-Hellman.
Hybrid cryptography
Combining a classical algorithm with a post-quantum one so the result stays secure as long as either component holds. It hedges against both a future quantum attack and an undiscovered flaw in the newer post-quantum scheme.