def _verify_required_claims_exist(jwt_claims):
    """Verifies that the required claims exist.

    Args:
      jwt_claims: the JWT claims to be verified.

    Raises:
      UnauthenticatedException: if some claim doesn't exist.
    """
    for claim_name in [u"aud", u"exp", u"iss", u"sub"]:
        if claim_name not in jwt_claims:
            raise suppliers.UnauthenticatedException(u'Missing "%s" claim' % claim_name)