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/tests/unit-tests/util/crypto.t.cpp b/tests/unit-tests/util/crypto.t.cpp
new file mode 100644
index 0000000..9bf9f59
--- /dev/null
+++ b/tests/unit-tests/util/crypto.t.cpp
@@ -0,0 +1,55 @@
+/* -*- 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.
+ */
+
+#include "util/crypto.hpp"
+
+#include "boost-test.hpp"
+
+namespace ndn {
+namespace crypto {
+namespace tests {
+
+BOOST_AUTO_TEST_SUITE(Util)
+BOOST_AUTO_TEST_SUITE(TestCrypto)
+
+BOOST_AUTO_TEST_CASE(Basic)
+{
+  const std::string testString = "Hello, world!";
+  ConstBufferPtr result;
+  BOOST_CHECK_NO_THROW(result = computeSha256Digest(reinterpret_cast<const uint8_t*>(testString.data()),
+                                                    testString.size()));
+
+  BOOST_CHECK_EQUAL(result->size(), SHA256_DIGEST_SIZE);
+
+  const uint8_t expectedSha256[] = {0x31, 0x5f, 0x5b, 0xdb, 0x76, 0xd0, 0x78, 0xc4,
+                                    0x3b, 0x8a, 0xc0, 0x06, 0x4e, 0x4a, 0x01, 0x64,
+                                    0x61, 0x2b, 0x1f, 0xce, 0x77, 0xc8, 0x69, 0x34,
+                                    0x5b, 0xfc, 0x94, 0xc7, 0x58, 0x94, 0xed, 0xd3};
+  BOOST_CHECK_EQUAL_COLLECTIONS(result->begin(), result->end(),
+                                expectedSha256, expectedSha256 + sizeof(expectedSha256));
+}
+
+BOOST_AUTO_TEST_SUITE_END() // TestCrypto
+BOOST_AUTO_TEST_SUITE_END() // Util
+
+} // namespace tests
+} // namespace crypto
+} // namespace ndn