diff --git a/core/node.hpp b/core/node.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014,  Regents of the University of California
+ *
+ * This file is part of NSL (NDN Signature Logger).
+ * See AUTHORS.md for complete list of NSL authors and contributors.
+ *
+ * NSL 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.
+ *
+ * NSL 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
+ * NSL, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @author Peizhen Guo <patrick.guopz@gmail.com>
+ */
+
+#ifndef NLS_CORE_NODE_HPP
+#define NLS_CORE_NODE_HPP
+#include <stddef.h>
+#include <time.h>
+
+#include <ndn-cxx/util/crypto.hpp>
+
+namespace nsl {
+
+class Index
+{
+public:
+  Index()
+  {
+  }
+
+  Index(const Index& idx)
+    : number(idx.number),
+      level(idx.level)
+  {
+  }
+
+  bool operator<(const Index& other) const
+  {
+    if (number < other.number)
+      {
+        return true;
+      }
+    else if (number == other.number)
+      {
+        return level < other.level;
+      }
+    else
+      {
+        return false;
+      }
+
+  }
+
+public:
+  uint64_t number;
+  uint64_t level;
+};
+
+
+class Node
+{
+public:
+
+  Node()
+  {
+  }
+
+
+  Node(uint64_t sequenceNumber, uint64_t level, time_t timestamp);
+
+
+  ~Node()
+  {
+  }
+
+
+  const Index&
+  getIndex() const;
+
+
+  time_t
+  getTimestamp() const;
+
+
+  void
+  setHash(ndn::ConstBufferPtr digest);
+
+
+  ndn::ConstBufferPtr
+  getHash() const;
+
+private:
+  ndn::ConstBufferPtr m_hash;
+  Index m_index;   // Node index.number starts from 0 (the index of current root)
+  time_t m_timeStamp;
+};
+
+} // namespace nsl
+
+#endif // NLS_CORE_NODE_HPP