Convert SharedSecret to a hexadecimal string about elliptic-curves HOT 2 CLOSED

   let alice_secret = EphemeralSecret::random(&mut OsRng);

    let bob_secret = EphemeralSecret::random(&mut OsRng);
    let bob_pk_bytes = EncodedPoint::from(bob_secret.public_key());

    let bob_public = PublicKey::from_sec1_bytes(bob_pk_bytes.as_ref())

    let alice_shared = alice_secret.diffie_hellman(&bob_public);
    let a = alice_shared.as_bytes().as_slice(); /// [f2, 422, ...]
 
    let mut shared_secret_hex_string = String::with_capacity(a.len() * 2);
    for &b in a {
        write!(&mut f, "{:02x}", b).unwrap();
    }
    shared_secret_hex_string