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/util/crypto.cpp b/src/util/crypto.cpp
index c480401..1e22c0e 100644
--- a/src/util/crypto.cpp
+++ b/src/util/crypto.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2014 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -19,52 +19,28 @@
  * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
  */
 
-#include "../common.hpp"
-
 #include "crypto.hpp"
 #include "../encoding/buffer-stream.hpp"
-#include "../security/cryptopp.hpp"
+
+#include "../security/v1/cryptopp.hpp"
 
 namespace ndn {
-
-void ndn_digestSha256(const uint8_t* data, size_t dataLength, uint8_t* digest)
-{
-  try
-    {
-      using namespace CryptoPP;
-
-      CryptoPP::SHA256 hash;
-      OBufferStream os;
-      StringSource(data, dataLength, true,
-                   new HashFilter(hash, new ArraySink(digest, crypto::SHA256_DIGEST_SIZE)));
-    }
-  catch (CryptoPP::Exception& e)
-    {
-      return;
-    }
-
-}
-
 namespace crypto {
 
 ConstBufferPtr
-sha256(const uint8_t* data, size_t dataLength)
+computeSha256Digest(const uint8_t* data, size_t dataLength)
 {
-  try
-    {
-      using namespace CryptoPP;
-
-      SHA256 hash;
-      OBufferStream os;
-      StringSource(data, dataLength, true, new HashFilter(hash, new FileSink(os)));
-      return os.buf();
-    }
-  catch (CryptoPP::Exception& e)
-    {
-      return ConstBufferPtr();
-    }
+  try {
+    CryptoPP::SHA256 hash;
+    OBufferStream os;
+    CryptoPP::StringSource(data, dataLength, true,
+      new CryptoPP::HashFilter(hash, new CryptoPP::FileSink(os)));
+    return os.buf();
+  }
+  catch (CryptoPP::Exception& e) {
+    return ConstBufferPtr();
+  }
 }
 
 } // namespace crypto
-
 } // namespace ndn