return XmlSignatureHelper.getDocument(lastParent);
} catch (XMLSignatureException se) {
if (se.getCause() instanceof InvalidKeyException) {
throw new XmlSignatureInvalidKeyException(se.getMessage(), se);
} else {
throw new XmlSignatureException(se);
}
} catch (GeneralSecurityException e) {
// like NoSuchAlgorithmException, InvalidAlgorithmParameterException, NoSuchProviderException