gistfile1.js

var crypto = require('xml-crypto')
    , Dom = require('xmldom').DOMParser
    , fs = require('fs')

var xml = fs.readFileSync('./windows_store_signature.xml', 'utf-8');
var doc = new Dom({ignoreWhiteSpace: true}).parseFromString(xml);    
xml = doc.firstChild.toString()
var signature = crypto.xpath(doc, "//*//*[local-name(.)='Signature' and namespace-uri(.)='http://www.w3.org/2000/09/xmldsig#']")[0];
var sig = new crypto.SignedXml();
sig.keyInfoProvider = new crypto.FileKeyInfo("./windows_store_certificate.pem");
sig.loadSignature(signature.toString());
var result = sig.checkSignature(xml);
if (result)
  console.log("signature is valid")
else
  console.log("signature is invalid: " + sig.validationErrors)