pub fn x448_ecdh(sk: &[u8; 56], peer_pk: &[u8; 56]) -> [u8; 56]Expand description
X448 Diffie-Hellman: derive a shared secret from our secret key and the peer’s public key.
Returns the 56-byte u-coordinate of sk * peer_pk. As with X25519,
this is the raw SP 800-56A “Z” value; callers feed it into a KDF
of their choice before using it for symmetric keying. See the
analogous doc in super::x25519 for the low-order defensive
check rationale.