XMLCipher cipher = XMLCipher.getInstance(algorithm);
cipher.init(XMLCipher.ENCRYPT_MODE, encryptingKey);
XPathFactory xpf = XPathFactory.newInstance();
XPath xpath = xpf.newXPath();
xpath.setNamespaceContext(new DSNamespaceContext());
for (String localName : localNames) {
String expression = "//*[local-name()='" + localName + "']";
Element elementToEncrypt =
(Element) xpath.evaluate(expression, document, XPathConstants.NODE);