private void checkArgumentsForBaseModeOnly(Key senderKey, byte[] psk, byte[] psk_id) {
    if (senderKey != null) {
      throw new UnsupportedOperationException("Asymmetric authentication not supported");
    }
    // PSK args can only be null if the application passed them in.
    Objects.requireNonNull(psk);
    Objects.requireNonNull(psk_id);
    if (psk.length > 0 || psk_id.length > 0) {
      throw new UnsupportedOperationException("PSK authentication not supported");
    }
  }
Implementation of {@link HpkeSpi}.  Should not be used directly, but rather by one
of the subclasses of {@link HpkeContext}.
common/src/main/java/org/conscrypt/HpkeImpl.java