pub fn diffie_hellman(private: &[u8; 32], public: &[u8; 33]) -> Result<[u8; 33]>Expand description
Diffie-Hellman in this group as OPAQUE-3DH defines it for P-256:
private * public, serialized as an element – the compressed point,
not the bare x-coordinate ordinary ECDH yields. public is validated.