byte[] bytes = Crypto.encryptKeyWithIES(contentKey,
feed.getUpdated().getTime(), recipient,
encryptionKeys.getPrivate());
String encoded = new Base64(0, null, true)
.encodeToString(bytes);
writer.startElement("EncryptedData",
"http://www.w3.org/2001/04/xmlenc#");
writer.startElement("CipherData",
"http://www.w3.org/2001/04/xmlenc#");
writer.startElement("CipherValue",
"http://www.w3.org/2001/04/xmlenc#");