choose any of the shared domains

lib/extensions/index.js

@@ -456,7 +456,8 @@ module.exports.pairPin = function (opts) {
 
     console.log('[pairPin] generating offer');
     var hri = require('human-readable-ids').hri;
-    var hrname = hri.random() + '.' + state.config.sharedDomain;
+    var i = Math.floor(Math.random() * state.config.sharedDomains.length);
+    var hrname = hri.random() + '.' + state.config.sharedDomains[i];
     // TODO check used / unused names and ports
     var authzData = {
       id: auth.id