diff --git a/src/security/conf/common.hpp b/src/security/conf/common.hpp
new file mode 100644
index 0000000..ba68e2a
--- /dev/null
+++ b/src/security/conf/common.hpp
@@ -0,0 +1,34 @@
+/* -*- 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>
+ * See COPYING for copyright and distribution information.
+ */
+
+#ifndef NDN_SECURITY_CONF_COMMON_HPP
+#define NDN_SECURITY_CONF_COMMON_HPP
+
+#include <string>
+#include <boost/property_tree/ptree.hpp>
+
+namespace ndn {
+namespace security {
+namespace conf {
+
+typedef boost::property_tree::ptree ConfigSection;
+
+class Error : public std::runtime_error
+{
+public:
+  explicit
+  Error(const std::string& what)
+    : std::runtime_error(what)
+  {
+  }
+};
+
+} // namespace conf
+} // namespace security
+} // namespace ndn
+
+#endif // NDN_SECURITY_CONF_COMMON_HPP