diff --git a/tools/ndnsec/set-default.hpp b/tools/ndnsec/set-default.hpp
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+++ b/tools/ndnsec/set-default.hpp
@@ -0,0 +1,110 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2014 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ *
+ * @author Yingdi Yu <http://irl.cs.ucla.edu/~yingdi/>
+ */
+
+#ifndef NDN_TOOLS_NDNSEC_SET_DEFAULT_HPP
+#define NDN_TOOLS_NDNSEC_SET_DEFAULT_HPP
+
+int
+ndnsec_set_default(int argc, char** argv)
+{
+  using namespace ndn;
+  namespace po = boost::program_options;
+
+  std::string certFileName;
+  bool isSetDefaultId = true;
+  bool isSetDefaultKey = false;
+  bool isSetDefaultCert = false;
+  std::string name;
+
+  po::options_description description("General Usage\n  ndnsec set-default [-h] [-k|c] name\nGeneral options");
+  description.add_options()
+    ("help,h", "produce help message")
+    ("default_key,k", "set default key of the identity")
+    ("default_cert,c", "set default certificate of the key")
+    ("name,n", po::value<std::string>(&name), "the name to set")
+    ;
+
+  po::positional_options_description p;
+  p.add("name", 1);
+  po::variables_map vm;
+  try
+    {
+      po::store(po::command_line_parser(argc, argv).options(description).positional(p).run(),
+                vm);
+      po::notify(vm);
+    }
+  catch (const std::exception& e)
+    {
+      std::cerr << "ERROR: " << e.what() << std::endl;
+      std::cerr << description << std::endl;
+      return 1;
+    }
+
+  if (vm.count("help") != 0)
+    {
+      std::cerr << description << std::endl;
+      return 0;
+    }
+
+  if (vm.count("name") == 0)
+    {
+      std::cerr << "ERROR: name is required!" << std::endl;
+      std::cerr << description << std::endl;
+      return 1;
+    }
+
+  KeyChain keyChain;
+
+  if (vm.count("default_key") != 0)
+    {
+      isSetDefaultKey = true;
+      isSetDefaultId = false;
+    }
+  else if (vm.count("default_cert") != 0)
+    {
+      isSetDefaultCert = true;
+      isSetDefaultId = false;
+    }
+
+  if (isSetDefaultId)
+    {
+      Name idName(name);
+      keyChain.setDefaultIdentity(idName);
+      return 0;
+    }
+  if (isSetDefaultKey)
+    {
+      Name keyName(name);
+      keyChain.setDefaultKeyNameForIdentity(keyName);
+      return 0;
+    }
+
+  if (isSetDefaultCert)
+    {
+      keyChain.setDefaultCertificateNameForKey(name);
+      return 0;
+    }
+
+  return 1;
+}
+#endif // NDN_TOOLS_NDNSEC_SET_DEFAULT_HPP