diff --git a/src/detail/ca-state.hpp b/src/detail/ca-state.hpp
new file mode 100644
index 0000000..2204f1c
--- /dev/null
+++ b/src/detail/ca-state.hpp
@@ -0,0 +1,94 @@
+/* -*- 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 "detail/ndncert-common.hpp"
+
+namespace ndn {
+namespace ndncert {
+
+// NDNCERT Request status enumeration
+enum class Status : uint16_t {
+  BEFORE_CHALLENGE = 0,
+  CHALLENGE = 1,
+  PENDING = 2,
+  SUCCESS = 3,
+  FAILURE = 4,
+  NOT_STARTED = 5,
+  ENDED = 6
+};
+
+// Convert request status to string
+std::string
+statusToString(Status status);
+
+/**
+ * @brief The state maintained by the Challenge modules
+ */
+struct ChallengeState
+{
+  ChallengeState(const std::string& challengeStatus, const time::system_clock::TimePoint& challengeTp,
+                 size_t remainingTries, time::seconds remainingTime,
+                 JsonSection&& challengeSecrets);
+  std::string m_challengeStatus;
+  time::system_clock::TimePoint m_timestamp;
+  size_t m_remainingTries;
+  time::seconds m_remainingTime;
+  JsonSection m_secrets;
+};
+
+/**
+ * @brief Represents a certificate request instance kept by the CA.
+ *
+ * ChallengeModule should take use of ChallengeState to keep state.
+ */
+class CaState
+{
+public:
+  CaState();
+  CaState(const Name& caName, const std::string& requestId, RequestType requestType, Status status,
+          const security::Certificate& cert, Block m_encryptionKey);
+  CaState(const Name& caName, const std::string& requestId, RequestType requestType, Status status,
+          const security::Certificate& cert, const std::string& challengeType,
+          const std::string& challengeStatus, const time::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::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