diff --git a/src/common.cpp b/src/common.cpp
new file mode 100644
index 0000000..da4c5fd
--- /dev/null
+++ b/src/common.cpp
@@ -0,0 +1,56 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2018, Regents of the University of California
+ *
+ * NAC 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.
+ *
+ * NAC 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 NAC library authors and contributors.
+ */
+
+#include "common.hpp"
+
+namespace ndn {
+namespace nac {
+
+Name
+convertKekNameToKdkPrefix(const Name& kekName, const ErrorCallback& onFailure)
+{
+  // * <access-namespace>/KEK/<key-id>  =>>   <access-namespace>/KDK/<key-id>
+  if (kekName.size() < 2 || kekName.get(-2) != KEK) {
+    onFailure(ErrorCode::KekInvalidName, "Invalid KEK name [" + kekName.toUri() + "]");
+    return {};
+  }
+
+  return kekName.getPrefix(-2).append(KDK).append(kekName.get(-1));
+}
+
+std::tuple<Name, Name, Name>
+extractKdkInfoFromCkName(const Name& ckDataName, const Name& ckName, const ErrorCallback& onFailure)
+{
+  // <full-ck-name-with-id> | /ENCRYPTED-BY/<kek-prefix>/NAC/KEK/<key-id>
+
+  if (ckDataName.size() < ckName.size() + 1 ||
+      ckDataName.getPrefix(ckName.size()) != ckName ||
+      ckDataName.get(ckName.size()) != ENCRYPTED_BY) {
+    onFailure(ErrorCode::CkInvalidName, "Invalid CK name [" + ckDataName.toUri() + "]");
+    return {};
+  }
+
+  auto kekName = ckDataName.getSubName(ckName.size() + 1);
+  return std::make_tuple(convertKekNameToKdkPrefix(kekName, onFailure),
+                         kekName.getPrefix(-2),
+                         kekName.getPrefix(-2).append("KEY").append(kekName.get(-1)));
+}
+
+} // namespace nac
+} // namespace ndn