diff --git a/src/security/additional-description.cpp b/src/security/additional-description.cpp
new file mode 100644
index 0000000..6aed34a
--- /dev/null
+++ b/src/security/additional-description.cpp
@@ -0,0 +1,197 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2015 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 "additional-description.hpp"
+#include "../util/concepts.hpp"
+#include "../encoding/block-helpers.hpp"
+
+namespace ndn {
+namespace security {
+
+BOOST_CONCEPT_ASSERT((boost::EqualityComparable<AdditionalDescription>));
+BOOST_CONCEPT_ASSERT((WireEncodable<AdditionalDescription>));
+BOOST_CONCEPT_ASSERT((WireEncodableWithEncodingBuffer<AdditionalDescription>));
+BOOST_CONCEPT_ASSERT((WireDecodable<AdditionalDescription>));
+static_assert(std::is_base_of<tlv::Error, AdditionalDescription::Error>::value,
+              "AdditionalDescription::Error must inherit from tlv::Error");
+
+static const size_t KEY_OFFSET = 0;
+static const size_t VALUE_OFFSET = 1;
+
+AdditionalDescription::AdditionalDescription(const Block& block)
+{
+  wireDecode(block);
+}
+
+const std::string&
+AdditionalDescription::get(const std::string& key) const
+{
+  auto it = m_info.find(key);
+  if (it == m_info.end())
+    throw Error("Entry does not exist for key (" + key + ")");
+
+  return it->second;
+}
+
+void
+AdditionalDescription::set(const std::string& key, const std::string& value)
+{
+  m_info[key] = value;
+}
+
+bool
+AdditionalDescription::has(const std::string& key) const
+{
+  return (m_info.find(key) != m_info.end());
+}
+
+AdditionalDescription::iterator
+AdditionalDescription::begin()
+{
+  return m_info.begin();
+}
+
+AdditionalDescription::iterator
+AdditionalDescription::end()
+{
+  return m_info.end();
+}
+
+AdditionalDescription::const_iterator
+AdditionalDescription::begin() const
+{
+  return m_info.begin();
+}
+
+AdditionalDescription::const_iterator
+AdditionalDescription::end() const
+{
+  return m_info.end();
+}
+
+template<encoding::Tag TAG>
+size_t
+AdditionalDescription::wireEncode(EncodingImpl<TAG>& encoder) const
+{
+  size_t totalLength = 0;
+
+  for (auto it = m_info.rbegin(); it != m_info.rend(); it++) {
+    size_t entryLength = 0;
+    entryLength += prependStringBlock(encoder, tlv::DescriptionValue, it->second);
+    entryLength += prependStringBlock(encoder, tlv::DescriptionKey, it->first);
+    entryLength += encoder.prependVarNumber(entryLength);
+    entryLength += encoder.prependVarNumber(tlv::DescriptionEntry);
+
+    totalLength += entryLength;
+  }
+
+  totalLength += encoder.prependVarNumber(totalLength);
+  totalLength += encoder.prependVarNumber(tlv::AdditionalDescription);
+  return totalLength;
+}
+
+template size_t
+AdditionalDescription::wireEncode<encoding::EncoderTag>(EncodingImpl<encoding::EncoderTag>& encoder) const;
+
+template size_t
+AdditionalDescription::wireEncode<encoding::EstimatorTag>(EncodingImpl<encoding::EstimatorTag>& encoder) const;
+
+const Block&
+AdditionalDescription::wireEncode() const
+{
+  if (m_wire.hasWire())
+    return m_wire;
+
+  EncodingEstimator estimator;
+  size_t estimatedSize = wireEncode(estimator);
+
+  EncodingBuffer buffer(estimatedSize, 0);
+  wireEncode(buffer);
+
+  m_wire = buffer.block();
+  m_wire.parse();
+
+  return m_wire;
+}
+
+void
+AdditionalDescription::wireDecode(const Block& wire)
+{
+   if (!wire.hasWire()) {
+    throw Error("The supplied block does not contain wire format");
+  }
+
+  m_wire = wire;
+  m_wire.parse();
+
+  if (m_wire.type() != tlv::AdditionalDescription)
+    throw Error("Unexpected TLV type when decoding AdditionalDescription");
+
+  Block::element_const_iterator it = m_wire.elements_begin();
+  while (it != m_wire.elements_end()) {
+    const Block& entry = *it;
+    entry.parse();
+
+    if (entry.type() != tlv::DescriptionEntry)
+      throw Error("Unexpected TLV type when decoding DescriptionEntry");
+
+    if (entry.elements_size() != 2)
+      throw Error("DescriptionEntry does not have two sub-TLVs");
+
+    if (entry.elements()[KEY_OFFSET].type() != tlv::DescriptionKey ||
+        entry.elements()[VALUE_OFFSET].type() != tlv::DescriptionValue)
+      throw Error("Invalid DescriptionKey or DescriptionValue field");
+
+    m_info[readString(entry.elements()[KEY_OFFSET])] = readString(entry.elements()[VALUE_OFFSET]);
+    it++;
+  }
+}
+
+bool
+AdditionalDescription::operator==(const AdditionalDescription& other) const
+{
+  return (m_info == other.m_info);
+}
+
+bool
+AdditionalDescription::operator!=(const AdditionalDescription& other) const
+{
+  return !(*this == other);
+}
+
+std::ostream&
+operator<<(std::ostream& os, const AdditionalDescription& other)
+{
+  size_t count = 0;
+  os << "(";
+  for (const auto& entry : other) {
+    if (count > 0)
+      os << ", ";
+    os << "(" << entry.first << ":" << entry.second << ")";
+    count++;
+  }
+  os << ")";
+
+  return os;
+}
+
+} // namespace security
+} // namespace ndn