Node.js does not always have the right libraries for Xml operations. When such libraries exist they are not always cross platform (read: work on windows). I've just published xml-crypto, the first xml digital signature library for node.
Recently, an anonymous poster tried to "slay" Microsoft for their Windows Phone platform shortcomings, but did he have his facts straight? Check out this comprehensive list that sets the record straight on 121 Windows Phone features (or lack thereof).