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+ndn-cxx version 0.5.1
+---------------------
+
+Release date: January 25, 2017
+
+.. note::
+   This is the last release of the library that supports :ref:`NDN Certificate format version 1
+   <Security Library Tutorial>` and the existing implementations of validators.  The upcoming
+   0.6.0 release will include multiple breaking changes of the security framework.
+
+Changes since version 0.5.0:
+
+New features:
+^^^^^^^^^^^^^
+
+- Add version 2 of the security framework (introduced in ``security::v2`` namespace)
+
+  * :ref:`NDN Certificate Format Version 2.0 <NDN Certificate Format Version 2.0>`
+    (:issue:`3103`)
+  * New Public Information Base (PIB) and Trusted Program Module (TPM) framework to manage
+    public/private keys and NDN Certificate version 2.0 (:issue:`2948`, :issue:`3202`)
+  * New KeyChain implementation (:issue:`2926`)
+  * New Validator implementation (:issue:`3289`, :issue:`1872`)
+  * New security-supporting utilities: trust anchor container and certificate cache
+  * Creation of `Command Interests
+    <https://redmine.named-data.net/projects/ndn-cxx/wiki/CommandInterest>`__ delegated to
+    :ndn-cxx:`CommandInterestSigner` class, while the new KeyChain only :ref:`signs Interests
+    <Signed Interest>` (:issue:`3912`)
+
+- Enable validator to fetch certificates directly from the signed/command interest sender
+  (:issue:`3921`)
+
+- Add UP and DOWN kinds to :ndn-cxx:`FaceEventNotification` (issue:`3794`)
+
+- Add support for NIC-associated permanent faces in FaceUri (:issue:`3522`)
+
+- Add support for CongestionMark and Ack NDNLPv2 fields (:issue:`3797`, :issue:`3931`)
+
+- Add StrategyChoice equality operators and formatted output (:issue:`3903`)
+
+Improvements and bug fixes
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Ensure that NACK callback is called for matching Interests, regardless of their nonce
+  (:issue:`3908`)
+
+- Optimize :ndn-cxx:`name::Component::compare` implementation (:issue:`3807`)
+
+- Fix memory leak in ndn-cxx:`Regex` (:issue:`3673`)
+
+- Correct NDNLPv2 rules for whether an unknown field can be ignored (:issue:`3884`)
+
+- Ensure that port numbers in FaceUri are 16 bits wide
+
+- Correct ValidityPeriod::isValid check (:issue:`2868`)
+
+- Fix encoding of type-specific TLV (:issue:`3914`)
+
+- Rename previously incorrectly named EcdsaKeyParams to EcKeyParams (:issue:`3135`)
+
+- Various documentation improvements, including ndn-cxx code style updates (:issue:`3795`, :issue:`3857`)
+
+Deprecated
+^^^^^^^^^^
+
+- Old security framework.  All old security framework classes are moved to
+  ``ndn::security::v1`` namespace in this release and will be removed in the next release.
+
+  * ``v1::KeyChain``, use :ndn-cxx:`v2::KeyChain` instead
+
+  * ``v1::Validator`` interface and all implementations of this interface (``ValidatorRegex``,
+    ``ValidatorConfig``, ``ValidatorNull``).  Use :ndn-cxx:`v2::Validator` and the
+    corresponding implementations of :ndn-cxx:`ValidationPolicy` interfaces (will be introduced
+    before 0.6.0 release).
+
+  * ``v1::SecPublicInfo`` and its implementation (``SecPublicInfoSqlite``), ``SecTpm`` and its
+    implementations (``SecTpmFile``, ``SecTpmOsx``).  These classes are internal implementation
+    and not intended to be used without ``v1::KeyChain``.  :ndn-cxx:`v2::KeyChain` internally
+    uses the newly introduced :ndn-cxx:`Pib` and :ndn-cxx:`Tpm` interfaces with their
+    corresponding implementations.
+
+  * ``v1::Certificate``, ``v1::IdentityCertificate``, ``v1::CertificateExtension``,
+    ``v1::CertificateSubjectDescription``, use :ndn-cxx:`v2::Certificate` and
+    :ndn-cxx:`AdditionalDescription`
+
+  * ``v1::SecuredBag``, use ``v2::SafeBag`` instead
+
+- Constant ``io::BASE_64``, use ``io::BASE64`` instead (:issue:`3741`)
+
+- Headers ``management/nfd-*``, use ``mgmt/nfd/*`` instead (:issue:`3760`)
+
+- ``ndn::crypto::sha256`` in favor of ``ndn::crypto::computeSha256Digest``
+
+- ``security/cryptopp.hpp`` header. Use ``security/v1/cryptopp.hpp`` when needed, avoid direct
+  include as CryptoPP dependency will be removed from future versions of the library.
+
+- ``security/identity-certificate.hpp`` header.  Use ``security/v1/identity-certificate.hpp`` instead.
+
+- ``ndn::PublicKey``, ``ndn::Certificate``, ``ndn::IdentityCertificate``,
+  ``ndn::CertificateExtension``, ``ndn::CertificateSubjectDescription``.  When necessary, use
+  ``security::v1::PublicKey``, ``security::v1::Certificate``, ``security::v1::IdentityCertificate``,
+  ``security::v1::CertificateExtension``, ``security::v1::CertificateSubjectDescription`` instead.
+  The next release will feature :ref:`a new version of NDN Certificate format
+  <NDN Certificate Format Version 2.0>`.