diff --git a/src/configuration.hpp b/src/configuration.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_CONFIG_HPP
+#define NDNCERT_CA_CONFIG_HPP
+
+#include "request-state.hpp"
+
+namespace ndn {
+namespace ndncert {
+
+struct CaConfigItem {
+  /**
+   * CA Name prefix (without /CA suffix).
+   */
+  Name m_caPrefix;
+  /**
+   * CA Information.
+   * Default: "".
+   */
+  std::string m_caInfo;
+  /**
+   * A list of parameter-keys for PROBE.
+   * Default: empty list.
+   */
+  std::list<std::string> m_probeParameterKeys;
+  /**
+   * Maximum allowed validity period of the certificate being requested.
+   * The value is in the unit of second.
+   * Default: one day (86400 seconds).
+   */
+  time::seconds m_maxValidityPeriod;
+  /**
+   * Maximum allowed suffix length of requested name.
+   * E.g., When its value is 2, at most 2 name components can be assigned after m_caPrefix.
+   * Default: none.
+   */
+  boost::optional<size_t> m_maxSuffixLength;
+  /**
+   * A list of supported challenges. Only CA side will have m_supportedChallenges.
+   * Default: empty list.
+   */
+  std::list<std::string> m_supportedChallenges;
+  /**
+   * CA's certificate. Only Client side will have m_cert.
+   * Default: nullptr.
+   */
+  std::shared_ptr<security::v2::Certificate> m_cert;
+
+  void
+  parse(const JsonSection& configJson);
+
+  JsonSection
+  toJson() const;
+
+private:
+  void
+  parseProbeParameters(const JsonSection& section);
+
+  void
+  parseChallengeList(const JsonSection& configSection);
+};
+
+/**
+ * @brief The name assignment function provided by the CA operator to generate available
+ * namecomponents.
+ * The function does not guarantee that all the returned names are available. Therefore the
+ * CA should further check the availability of each returned name and remove unavailable results.
+ *
+ * @p vector, input, a list of parameter key-value pair used for name assignment.
+ * @return a vector containing the possible namespaces derived from the parameters.
+ */
+using NameAssignmentFunc = function<std::vector<std::string>(const std::vector<std::tuple<std::string, std::string>>)>;
+
+/**
+ * @brief The function would be invoked whenever the certificate request status is updated.
+ * The callback is used to notice the CA application or CA command line tool. The callback is
+ * fired whenever a request instance is created, challenge status is updated, and when certificate
+ * is issued.
+ *
+ * @p RequestState, input, the state of the certificate request whose status is updated.
+ */
+using StatusUpdateCallback = function<void(const RequestState&)>;
+
+/**
+ * @brief CA's configuration on NDNCERT.
+ * For CA configuration format, please refer to:
+ *   https://github.com/named-data/ndncert/wiki/NDNCERT-Protocol-0.3#213-ca-profile
+ *
+ * The format of CA configuration in JSON
+ * {
+ *  "ca-prefix": "",
+ *  "ca-info": "",
+ *  "max-validity-period": "",
+ *  "max-suffix-length": "",
+ *  "probe-parameters":
+ *  [
+ *    {"probe-parameter-key": ""},
+ *    {"probe-parameter-key": ""}
+ *  ]
+ *  "supported-challenges":
+ *  [
+ *    {"challenge": ""},
+ *    {"challenge": ""}
+ *  ]
+ * }
+ */
+class CaConfig {
+public:
+  /**
+   * Load CA configuration from the file.
+   * @throw std::runtime_error when config file cannot be correctly parsed.
+   */
+  void
+  load(const std::string& fileName);
+
+  void
+  save(const std::string& fileName) const;
+
+  CaConfigItem m_caItem;
+  /**
+   * NameAssignmentFunc Callback function
+   */
+  NameAssignmentFunc m_nameAssignmentFunc;
+  /**
+   * StatusUpdate Callback function
+   */
+  StatusUpdateCallback m_statusUpdateCallback;
+};
+
+/**
+ * @brief Represents Client configuration
+ *
+ * For Client configuration format, please refer to:
+ *   https://github.com/named-data/ndncert/wiki/Client-Configuration-Sample
+ */
+class ClientConfig {
+public:
+  /**
+   * @throw std::runtime_error when config file cannot be correctly parsed.
+   */
+  void
+  load(const std::string& fileName);
+
+  /**
+   * @throw std::runtime_error when config file cannot be correctly parsed.
+   */
+  void
+  load(const JsonSection& configSection);
+
+  void
+  save(const std::string& fileName) const;
+
+  void
+  removeCaItem(const Name& caName);
+
+  std::list<CaConfigItem> m_caItems;
+};
+
+}  // namespace ndncert
+}  // namespace ndn
+
+#endif  // NDNCERT_CA_CONFIG_HPP