diff --git a/src/protocol-detail/challenge.cpp b/src/protocol-detail/challenge.cpp
new file mode 100644
index 0000000..f1fed27
--- /dev/null
+++ b/src/protocol-detail/challenge.cpp
@@ -0,0 +1,44 @@
+/* -*- 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 "challenge.hpp"
+#include "../ndncert-common.hpp"
+#include "../certificate-request.hpp"
+
+namespace ndn {
+namespace ndncert {
+
+Block
+CHALLENGE::encodeDataPayload(const CertificateRequest& request)
+{
+  Block response = makeEmptyBlock(tlv_encrypted_payload);
+  makeNonNegativeIntegerBlock(tlv_status, request.m_status);
+  makeStringBlock(tlv_challenge_status, request.m_challengeStatus);
+  makeNonNegativeIntegerBlock(tlv_remaining_tries, request.m_remainingTries);
+  makeNonNegativeIntegerBlock(tlv_remaining_time, request.m_remainingTime);
+  response.parse();
+  return response;
+}
+
+} // namespace ndncert
+} // namespace ndn
+
+
+