diff --git a/src/ca-state.hpp b/src/ca-state.hpp
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+++ b/src/ca-state.hpp
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+/* -*- 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.
+ */
+
+#ifndef NDNCERT_CA_STATE_HPP
+#define NDNCERT_CA_STATE_HPP
+
+#include "ndncert-common.hpp"
+
+namespace ndn {
+namespace ndncert {
+
+struct ChallengeState {
+  ChallengeState(const std::string& challengeStatus, const system_clock::TimePoint& challengeTp,
+                 size_t remainingTries, time::seconds remainingTime,
+                 JsonSection&& challengeSecrets);
+  std::string m_challengeStatus;
+  system_clock::TimePoint m_timestamp;
+  size_t m_remainingTries;
+  time::seconds m_remainingTime;
+  JsonSection m_secrets;
+};
+
+/**
+ * @brief Represents a certificate request instance.
+ *
+ * ChallengeModule should take use of m_challengeStatus, m_challengeInstruction and
+ * m_challengeDefinedField to finish verification.
+ *
+ */
+class CaState {
+
+public:
+  CaState();
+  CaState(const Name& caName, const std::string& requestId, RequestType requestType, Status status,
+          const security::v2::Certificate& cert, Block m_encryptionKey);
+  CaState(const Name& caName, const std::string& requestId, RequestType requestType, Status status,
+          const security::v2::Certificate& cert, const std::string& challengeType,
+          const std::string& challengeStatus, const system_clock::TimePoint& challengeTp,
+          size_t remainingTries, time::seconds remainingTime, JsonSection&& challengeSecrets,
+          Block m_encryptionKey);
+
+public:
+  Name m_caPrefix;
+  std::string m_requestId;
+  RequestType m_requestType;
+  Status m_status;
+  security::v2::Certificate m_cert;
+  Block m_encryptionKey;
+
+  std::string m_challengeType;
+  boost::optional<ChallengeState> m_challengeState;
+};
+
+std::ostream&
+operator<<(std::ostream& os, const CaState& request);
+
+}  // namespace ndncert
+}  // namespace ndn
+
+#endif  // NDNCERT_CA_STATE_HPP