XXX Support compressed point format.
        XXX Check that the pubkey received is on the curve.

def register_pubkey(self):
        """
        XXX Support compressed point format.
        XXX Check that the pubkey received is on the curve.
        """
        # point_format = 0
        # if self.point[0] in [b'\x02', b'\x03']:
        #    point_format = 1

        curve_name = _tls_named_curves[self.named_curve]
        curve = ec._CURVE_TYPES[curve_name]()
        import_point = ec.EllipticCurvePublicNumbers.from_encoded_point
        pubnum = import_point(curve, self.point)
        s = self.tls_session
        s.server_kx_pubkey = pubnum.public_key(default_backend())

        if not s.client_kx_ecdh_params:
            s.client_kx_ecdh_params = curve