init design

lib/util/mac.js

@@ -0,0 +1,18 @@
+var crypto = require('crypto');
+
+'use strict';
+
+module.exports = {
+  generate: generate
+}
+
+function generate(data) {
+  var sha1sum = crypto.createHash('sha1');
+  sha1sum.update(data);
+  var s = sha1sum.digest('hex');
+  var i = -1;
+  return 'xx:xx:xx:xx:xx:xx'.replace(/[x]/g, function(c) {
+    i += 1;
+    return s[i];
+  }).toUpperCase();
+};