diff --git a/src/group-manager.cpp b/src/group-manager.cpp
new file mode 100644
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--- /dev/null
+++ b/src/group-manager.cpp
@@ -0,0 +1,207 @@
+/* -*- 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>
+ */
+
+#include "group-manager.hpp"
+#include "encryptor.hpp"
+#include "encrypted-content.hpp"
+
+#include <map>
+
+namespace ndn {
+namespace gep {
+
+static const std::string E_KEY_COMPONENT = "E-KEY";
+static const std::string D_KEY_COMPONENT = "D-KEY";
+
+GroupManager::GroupManager(const Name& managedNamespace, const std::string& dbDir,
+                           const int paramLength, const int freshPeriod)
+  : m_namespace(managedNamespace)
+  , m_db(dbDir)
+  , m_paramLength(paramLength)
+  , m_freshPeriod(freshPeriod)
+{
+}
+
+std::list<Data>
+GroupManager::getGroupKey(const TimeStamp& timeslot)
+{
+  std::map<Name, Buffer> memberKeys;
+  std::list<Data> result;
+
+  // get time interval
+  Interval finalInterval = calculateInterval(timeslot, memberKeys);
+  if (finalInterval.isValid() == false)
+    return result;
+
+  std::string startTs = boost::posix_time::to_iso_string(finalInterval.getStartTime());
+  std::string endTs = boost::posix_time::to_iso_string(finalInterval.getEndTime());
+
+  // generate the pri key and pub key
+  Buffer priKeyBuf, pubKeyBuf;
+  generateKeyPairs(priKeyBuf, pubKeyBuf);
+
+  // add the first element to the result
+  // E-KEY (public key) data packet name convention:
+  // /<data_type>/E-KEY/[start-ts]/[end-ts]
+  Data data = createEKeyData(startTs, endTs, pubKeyBuf);
+  result.push_back(data);
+
+  // encrypt pri key with pub key from certificate
+  for (const auto& entry : memberKeys) {
+    const Name& keyName = entry.first;
+    const Buffer& certKey = entry.second;
+
+    // generate the name of the packet
+    // D-KEY (private key) data packet name convention:
+    // /<data_type>/D-KEY/[start-ts]/[end-ts]/[member-name]
+    data = createDKeyData(startTs, endTs, keyName, priKeyBuf, certKey);
+    result.push_back(data);
+  }
+  return result;
+}
+
+void
+GroupManager::addSchedule(const std::string& scheduleName, const Schedule& schedule)
+{
+  m_db.addSchedule(scheduleName, schedule);
+}
+
+void
+GroupManager::deleteSchedule(const std::string& scheduleName)
+{
+  m_db.deleteSchedule(scheduleName);
+}
+
+void
+GroupManager::updateSchedule(const std::string& scheduleName, const Schedule& schedule)
+{
+  m_db.updateSchedule(scheduleName, schedule);
+}
+
+void
+GroupManager::addMember(const std::string& scheduleName, const Data& memCert)
+{
+  IdentityCertificate cert(memCert);
+  m_db.addMember(scheduleName, cert.getPublicKeyName(), cert.getPublicKeyInfo().get());
+}
+
+void
+GroupManager::removeMember(const Name& identity)
+{
+  m_db.deleteMember(identity);
+}
+
+void
+GroupManager::updateMemberSchedule(const Name& identity, const std::string& scheduleName)
+{
+  m_db.updateMemberSchedule(identity, scheduleName);
+}
+
+Interval
+GroupManager::calculateInterval(const TimeStamp& timeslot, std::map<Name, Buffer>& memberKeys)
+{
+  // prepare
+  Interval positiveResult;
+  Interval negativeResult;
+  Interval tempInterval;
+  Interval finalInterval;
+  bool isPositive;
+  memberKeys.clear();
+
+  // get the all intervals from schedules
+  for (const std::string& scheduleName : m_db.listAllScheduleNames()) {
+
+    const Schedule& schedule = m_db.getSchedule(scheduleName);
+    std::tie(isPositive, tempInterval) = schedule.getCoveringInterval(timeslot);
+
+    if (isPositive) {
+      if (!positiveResult.isValid())
+        positiveResult = tempInterval;
+      positiveResult && tempInterval;
+
+      std::map<Name, Buffer> m = m_db.getScheduleMembers(scheduleName);
+      memberKeys.insert(m.begin(), m.end());
+    }
+    else {
+      if (!negativeResult.isValid())
+        negativeResult = tempInterval;
+      negativeResult && tempInterval;
+    }
+  }
+  if (!positiveResult.isValid()) {
+    // return invalid interval when there is no member has interval covering the time slot
+    return Interval(false);
+  }
+
+  // get the final interval result
+  if (negativeResult.isValid())
+    finalInterval = positiveResult && negativeResult;
+  else
+    finalInterval = positiveResult;
+
+  return finalInterval;
+}
+
+void
+GroupManager::generateKeyPairs(Buffer& priKeyBuf, Buffer& pubKeyBuf) const
+{
+  RandomNumberGenerator rng;
+  RsaKeyParams params(m_paramLength);
+  algo::EncryptParams eparams(tlv::AlgorithmRsaPkcs);
+  DecryptKey<algo::Rsa> privateKey = algo::Rsa::generateKey(rng, params);
+  priKeyBuf = privateKey.getKeyBits();
+  EncryptKey<algo::Rsa> publicKey = algo::Rsa::deriveEncryptKey(priKeyBuf);
+  pubKeyBuf = publicKey.getKeyBits();
+}
+
+
+Data
+GroupManager::createEKeyData(const std::string& startTs, const std::string& endTs,
+                             const Buffer& pubKeyBuf)
+{
+  Name dataName(m_namespace);
+  dataName.append(E_KEY_COMPONENT).append(startTs).append(endTs);
+  Data data(dataName);
+  data.setFreshnessPeriod(time::hours(m_freshPeriod));
+  data.setContent(pubKeyBuf.get(), pubKeyBuf.size());
+  m_keyChain.sign(data);
+  return data;
+}
+
+Data
+GroupManager::createDKeyData(const std::string& startTs, const std::string& endTs,
+                             const Name& keyName, const Buffer& priKeyBuf,
+                             const Buffer& certKey)
+{
+  Name dataName(m_namespace);
+  dataName.append(D_KEY_COMPONENT);
+  dataName.append(startTs).append(endTs).append(keyName.getPrefix(-1));
+  Data data = Data(dataName);
+  data.setFreshnessPeriod(time::hours(m_freshPeriod));
+  algo::EncryptParams eparams(tlv::AlgorithmRsaPkcs);
+  algo::encryptData(data, priKeyBuf.buf(), priKeyBuf.size(), keyName,
+                    certKey.buf(), certKey.size(), eparams);
+  m_keyChain.sign(data);
+  return data;
+}
+
+} // namespace ndn
+} // namespace ndn