DER encoding: Implement DerNode and subclasses.
diff --git a/ndn-cpp/encoding/der/der-exception.cpp b/ndn-cpp/encoding/der/der-exception.cpp
new file mode 100644
index 0000000..84ab5c1
--- /dev/null
+++ b/ndn-cpp/encoding/der/der-exception.cpp
@@ -0,0 +1,29 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/**
+ * Copyright (C) 2013 Regents of the University of California.
+ * @author: Yingdi Yu <yingdi@cs.ucla.edu>
+ * @author: Jeff Thompson <jefft0@remap.ucla.edu>
+ * See COPYING for copyright and distribution information.
+ */
+
+#include "der-exception.hpp"
+
+using namespace std;
+
+namespace ndn {
+
+namespace der
+{
+
+DerException::DerException(const string& errorMessage) throw()
+ : errorMessage_(errorMessage)
+{
+}
+
+DerException::~DerException() throw()
+{
+}
+
+} // der
+
+}