code: def ec_construct_public(num):
      
      ecpn = ec.EllipticCurvePublicNumbers(num['x'], num['y'],
                                           NIST2SEC[as_unicode(num['crv'])]())
      return ecpn.public_key(default_backend())
docs: Given a set of values on public attributes build a elliptic curve
      public key instance.
  
      :param num: A dictionary with public attributes and their values
      :return: A
          cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey
          instance.