diff --git a/src/consumer.hpp b/src/consumer.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2015,  Regents of the University of California
+ *
+ * This file is part of ndn-group-encrypt (Group-based Encryption Protocol for NDN).
+ * See AUTHORS.md for complete list of ndn-group-encrypt authors and contributors.
+ *
+ * ndn-group-encrypt 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.
+ *
+ * ndn-group-encrypt 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 a copy of the GNU General Public License along with
+ * ndn-group-encrypt, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @author Zhiyi Zhang <dreamerbarrychang@gmail.com>
+ * @author Yingdi Yu <yingdi@cs.ucla.edu>
+ */
+
+#ifndef NDN_GEP_CONSUMER_HPP
+#define NDN_GEP_CONSUMER_HPP
+
+#include "algo/rsa.hpp"
+#include "algo/aes.hpp"
+#include "consumer-db.hpp"
+#include "error-code.hpp"
+
+#include <ndn-cxx/security/validator-null.hpp>
+#include <ndn-cxx/face.hpp>
+
+namespace ndn {
+namespace gep {
+
+typedef function<void (const Data&, const Buffer&)> ConsumptionCallBack;
+
+/**
+ * @brief Consumer in group-based encryption protocol
+ */
+class Consumer
+{
+private:
+  typedef function<void (const Buffer&)> PlainTextCallBack;
+
+public:
+  /**
+   * @brief Create a consumer instance
+   *
+   * @param face The face used for key fetching
+   * @param groupName The reading group name that the consumer belongs to
+   * @param consumerName The identity of the consumer
+   * @param dbDir The path to database storing decryption key
+   */
+  Consumer(Face& face, const Name& groupName, const Name& consumerName, const std::string& dbDir);
+
+  /**
+   * @brief Send out the Interest packet to fetch content packet with @p dataName.
+   *
+   * @param consumptionCallBack The callback when requested data is decrypted
+   * @param errorCallBack The callback when error happens in consumption
+   */
+  void
+  consume(const Name& dataName,
+          const ConsumptionCallBack& consumptionCallBack,
+          const ErrorCallBack& errorCallBack);
+
+  /**
+   * @brief Set the group name to @p groupName.
+   */
+  void
+  setGroup(const Name& groupName);
+
+  /**
+   * @brief Add new decryption key with @p keyName and @p keyBuf.
+   */
+  void
+  addDecryptionKey(const Name& keyName, const Buffer& keyBuf);
+
+PUBLIC_WITH_TESTS_ELSE_PRIVATE:
+
+  /**
+   * @brief Decrypt @p encryptedBlock using @p keyBits
+   *
+   * Invoke @p plainTextCallBack when block is decrypted, otherwise @p errorCallBack.
+   */
+  void
+  decrypt(const Block& encryptedBlock,
+          const Buffer& keyBits,
+          const PlainTextCallBack& plainTextCallBack,
+          const ErrorCallBack& errorCallBack);
+
+  /**
+   * @brief Decrypt @p data.
+   *
+   * Invoke @p plainTextCallBack when block is decrypted, otherwise @p errorCallBack.
+   */
+  void
+  decryptContent(const Data& data,
+                 const PlainTextCallBack& plainTextCallBack,
+                 const ErrorCallBack& errorCallBack);
+
+  /**
+   * @brief Decrypt @p cKeyData.
+   *
+   * Invoke @p plainTextCallBack when block is decrypted, otherwise @p errorCallBack.
+   */
+  void
+  decryptCKey(const Data& cKeyData,
+              const PlainTextCallBack& plainTextCallBack,
+              const ErrorCallBack& errorCallBack);
+
+  /**
+   * @brief Decrypt @p dKeyData.
+   *
+   * Invoke @p plainTextCallBack when block is decrypted, otherwise @p errorCallBack.
+   */
+  void
+  decryptDKey(const Data& dKeyData,
+              const PlainTextCallBack& plainTextCallBack,
+              const ErrorCallBack& errorCallBack);
+
+
+  /**
+   * @brief Get the buffer of decryption key with @p decryptionKeyName from database.
+   *
+   * @return Null buffer when there is no decryption key with @p decryptionKeyName.
+   */
+  const Buffer
+  getDecryptionKey(const Name& decryptionKeyName);
+
+private:
+  ConsumerDB m_db;
+  unique_ptr<Validator> m_validator;
+  Face& m_face;
+  Name m_groupName;
+  Name m_consumerName;
+
+  std::map<Name, Buffer> m_cKeyMap;
+  std::map<Name, Buffer> m_dKeyMap;
+};
+
+} // namespace gep
+} // namespace ndn
+
+#endif // NDN_GEP_CONSUMER_HPP