diff --git a/src/util/digest.cpp b/src/util/digest.cpp
new file mode 100644
index 0000000..bb2201d
--- /dev/null
+++ b/src/util/digest.cpp
@@ -0,0 +1,136 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2014 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library 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 Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#include "digest.hpp"
+
+namespace ndn {
+namespace util {
+
+template<typename Hash>
+Digest<Hash>::Digest()
+{
+  reset();
+}
+
+template<typename Hash>
+void
+Digest<Hash>::reset()
+{
+  m_hash.Restart();
+  m_buffer = make_shared<Buffer>(m_hash.DigestSize());
+  m_isInProcess = false;
+  m_isFinalized = false;
+}
+
+template<typename Hash>
+void
+Digest<Hash>::finalize()
+{
+  // return immediately if Digest is finalized already.
+  if (m_isFinalized)
+    return;
+
+  m_hash.Final(m_buffer->get());
+
+  m_isFinalized = true;
+}
+
+template<typename Hash>
+ConstBufferPtr
+Digest<Hash>::computeDigest()
+{
+  finalize();
+  return m_buffer;
+}
+
+template<typename Hash>
+bool
+Digest<Hash>::operator==(Digest<Hash>& digest)
+{
+  return *computeDigest() == *digest.computeDigest();
+}
+
+template<typename Hash>
+Digest<Hash>&
+Digest<Hash>::operator<<(Digest<Hash>& src)
+{
+  ConstBufferPtr buffer = src.computeDigest();
+  update(buffer->get(), buffer->size());
+
+  return *this;
+}
+
+template<typename Hash>
+Digest<Hash>&
+Digest<Hash>::operator<<(const std::string& str)
+{
+  update(reinterpret_cast<const uint8_t*>(str.c_str()), str.size());
+
+  return *this;
+}
+
+template<typename Hash>
+Digest<Hash>&
+Digest<Hash>::operator<<(const Block& block)
+{
+  update(block.wire(), block.size());
+
+  return *this;
+}
+
+template<typename Hash>
+Digest<Hash>&
+Digest<Hash>::operator<<(uint64_t value)
+{
+  update(reinterpret_cast<const uint8_t*>(&value), sizeof(uint64_t));
+
+  return *this;
+}
+
+template<typename Hash>
+void
+Digest<Hash>::update(const uint8_t* buffer, size_t size)
+{
+  // cannot update Digest when it has been finalized
+  if (m_isFinalized)
+    throw Error("Digest has been already finalized");
+
+  m_hash.Update(buffer, size);
+
+  m_isInProcess = true;
+}
+
+template<typename Hash>
+ConstBufferPtr
+Digest<Hash>::computeDigest(const uint8_t* buffer, size_t size)
+{
+  Hash hash;
+  BufferPtr result = make_shared<Buffer>(hash.DigestSize());
+  hash.Update(buffer, size);
+  hash.Final(result->get());
+
+  return result;
+}
+
+template class Digest<CryptoPP::SHA256>;
+
+} // namespace util
+} // namespace ndn