diff --git a/src/name-assignment/assignment-func.cpp b/src/name-assignment/assignment-func.cpp
new file mode 100644
index 0000000..6a55cc2
--- /dev/null
+++ b/src/name-assignment/assignment-func.cpp
@@ -0,0 +1,59 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2017-2020, Regents of the University of California.
+ *
+ * This file is part of ndncert, a certificate management system based on NDN.
+ *
+ * ndncert is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * ndncert 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 General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License along with
+ * ndncert, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndncert authors and contributors.
+ */
+
+#include "assignment-func.hpp"
+#include <ndn-cxx/util/random.hpp>
+
+namespace ndn {
+namespace ndncert {
+
+NameAssignmentFunc::NameAssignmentFunc(const std::string& factoryType, const std::string& format)
+  : FACTORY_TYPE(factoryType)
+{
+  size_t index = 0, startIndex = 0;
+  while ((index = format.find("/", startIndex)) != std::string::npos) {
+    auto component = format.substr(startIndex, index - startIndex);
+    if (!component.empty()) {
+      m_nameFormat.push_back(component);
+    }
+    startIndex = index + 1;
+  }
+  if (startIndex != format.size()) {
+    m_nameFormat.push_back(format.substr(startIndex));
+  }
+}
+
+unique_ptr<NameAssignmentFunc>
+NameAssignmentFunc::createNameAssignmentFunc(const std::string& challengeType, const std::string& format)
+{
+  FuncFactoryFactory& factory = getFactory();
+  auto i = factory.find(challengeType);
+  return i == factory.end() ? nullptr : i->second(format);
+}
+
+NameAssignmentFunc::FuncFactoryFactory&
+NameAssignmentFunc::getFactory()
+{
+  static NameAssignmentFunc::FuncFactoryFactory factory;
+  return factory;
+}
+
+} // namespace ndncert
+} // namespace ndn