security: Reorganizing source code to prepare for support of two version of NDN certificates

This commit also removes unused ndn_digestSha256 function and deprecates
crypto::sha256 in favor of crypto::computeSha256Digest in util/crypto.hpp.

Change-Id: I24ee50ff073a96b868633bdf2cfade412d3605f3
Refs: #3098
diff --git a/src/security/v1/identity-certificate.hpp b/src/security/v1/identity-certificate.hpp
new file mode 100644
index 0000000..7ea4fe4
--- /dev/null
+++ b/src/security/v1/identity-certificate.hpp
@@ -0,0 +1,110 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2016 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.
+ *
+ * @author Yingdi Yu <http://irl.cs.ucla.edu/~yingdi/>
+ */
+
+#ifndef NDN_SECURITY_V1_IDENTITY_CERTIFICATE_HPP
+#define NDN_SECURITY_V1_IDENTITY_CERTIFICATE_HPP
+
+#include "../../common.hpp"
+#include "certificate.hpp"
+
+namespace ndn {
+namespace security {
+namespace v1 {
+
+class IdentityCertificate : public Certificate
+{
+public:
+  class Error : public Certificate::Error
+  {
+  public:
+    explicit
+    Error(const std::string& what)
+      : Certificate::Error(what)
+    {
+    }
+  };
+
+  /**
+   * @brief The default constructor.
+   */
+  IdentityCertificate();
+
+  /**
+   * @brief Create an IdentityCertificate from the content in the data packet.
+   * @param data The data packet with the content to decode.
+   */
+  explicit
+  IdentityCertificate(const Data& data);
+
+  /**
+   * @brief Create an IdentityCertificate from a block.
+   * @param block The raw block of the certificate.
+   */
+  explicit
+  IdentityCertificate(const Block& block);
+
+  void
+  wireDecode(const Block& wire);
+
+  void
+  setName(const Name& name);
+
+  const Name&
+  getPublicKeyName() const
+  {
+    return m_publicKeyName;
+  }
+
+  static bool
+  isIdentityCertificate(const Certificate& certificate);
+
+  /**
+   * @brief Get the public key name from the full certificate name.
+   * @param certificateName The full certificate name.
+   * @return The related public key name.
+   */
+  static Name
+  certificateNameToPublicKeyName(const Name& certificateName);
+
+private:
+  static bool
+  isCorrectName(const Name& name);
+
+  void
+  setPublicKeyName();
+
+protected:
+  Name m_publicKeyName;
+};
+
+} // namespace v1
+} // namespace security
+
+#ifdef NDN_CXX_KEEP_SECURITY_V1_ALIASES
+/// @deprecated When needed, use explicit namespace
+using security::v1::IdentityCertificate;
+#endif // NDN_CXX_KEEP_SECURITY_V1_ALIASES
+
+} // namespace ndn
+
+#endif // NDN_SECURITY_V1_IDENTITY_CERTIFICATE_HPP