Finish implementing some encryption in the network protocols with AES

lib/utils/Hashing.dart

@@ -8,6 +8,10 @@ class Hashing {
     return bytes2Hash(md5SumStr(input));
   }
 
+  static String llMD5String(String src, int nonce) {
+    return md5Hash("${src}:${nonce}");
+  }
+
   /// This will generate the Sha1 bytes and hash it using #bytes2Hash
   static String sha1Hash(String input) {
     return bytes2Hash(sha1SumStr(input));