diff --git a/src/ndncert-common.hpp b/src/ndncert-common.hpp
index b5c8d0f..d052d62 100644
--- a/src/ndncert-common.hpp
+++ b/src/ndncert-common.hpp
@@ -51,6 +51,9 @@
 #include <boost/assert.hpp>
 #include <boost/noncopyable.hpp>
 #include <boost/throw_exception.hpp>
+#include <boost/property_tree/info_parser.hpp>
+#include <boost/property_tree/json_parser.hpp>
+#include <boost/property_tree/ptree.hpp>
 
 namespace ndn {
 namespace ndncert {
@@ -152,6 +155,14 @@
 
 std::string requestTypeToString(RequestType type);
 
+typedef boost::property_tree::ptree JsonSection;
+
+std::string
+convertJson2String(const JsonSection& json);
+
+JsonSection
+convertString2Json(const std::string& jsonContent);
+
 }  // namespace ndncert
 }  // namespace ndn