diff --git a/src/leaf.cpp b/src/leaf.cpp
new file mode 100644
index 0000000..129b1ea
--- /dev/null
+++ b/src/leaf.cpp
@@ -0,0 +1,78 @@
+/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2012-2014 University of California, Los Angeles
+ *
+ * This file is part of ChronoSync, synchronization library for distributed realtime
+ * applications for NDN.
+ *
+ * ChronoSync 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.
+ *
+ * ChronoSync 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
+ * ChronoSync, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @author Zhenkai Zhu <http://irl.cs.ucla.edu/~zhenkai/>
+ * @author Chaoyi Bian <bcy@pku.edu.cn>
+ * @author Alexander Afanasyev <http://lasr.cs.ucla.edu/afanasyev/index.html>
+ */
+
+#include "leaf.hpp"
+
+namespace chronosync {
+
+Leaf::Leaf(const Name& sessionName, const SeqNo& seq)
+  : m_sessionName(sessionName)
+  , m_seq(seq)
+{
+  updateDigest();
+}
+
+Leaf::Leaf(const Name& userPrefix, uint64_t session, const SeqNo& seq)
+  : m_sessionName(userPrefix)
+  , m_seq(seq)
+{
+  m_sessionName.appendNumber(session);
+  updateDigest();
+}
+
+Leaf::~Leaf()
+{
+}
+
+ndn::ConstBufferPtr
+Leaf::getDigest() const
+{
+  return m_digest.computeDigest();
+}
+
+void
+Leaf::setSeq(const SeqNo& seq)
+{
+  if (seq > m_seq) {
+    m_seq = seq;
+    updateDigest();
+  }
+}
+
+void
+Leaf::updateDigest()
+{
+  m_digest.reset();
+  m_digest << getSessionName().wireEncode() << getSeq();
+  m_digest.computeDigest();
+}
+
+std::ostream&
+operator<<(std::ostream& os, const Leaf& leaf)
+{
+  os << leaf.getSessionName() << "(" << leaf.getSeq() << ")";
+  return os;
+}
+
+
+} // namespace chronosync