Move key-chain to security subdirectory.
diff --git a/ndn-cpp/node.cpp b/ndn-cpp/node.cpp
index 369f3ca..a93ebd7 100644
--- a/ndn-cpp/node.cpp
+++ b/ndn-cpp/node.cpp
@@ -57,6 +57,7 @@
 {
   if (ndndIdData->getSignedInfo().getPublisherPublicKeyDigest().getPublisherPublicKeyDigest().size() > 0) {
     // Set the ndndId_ and continue.
+    // TODO: If there are multiple connected hubs, the NDN ID is really stored per connected hub.
     info_->node_.ndndId_ = ndndIdData->getSignedInfo().getPublisherPublicKeyDigest().getPublisherPublicKeyDigest();
     info_->node_.registerPrefixHelper(info_->prefix_, info_->onInterest_, info_->flags_);
   }
diff --git a/ndn-cpp/key-chain.cpp b/ndn-cpp/security/key-chain.cpp
similarity index 98%
rename from ndn-cpp/key-chain.cpp
rename to ndn-cpp/security/key-chain.cpp
index b917405..65d61bb 100644
--- a/ndn-cpp/key-chain.cpp
+++ b/ndn-cpp/security/key-chain.cpp
@@ -4,9 +4,9 @@
  */
 
 #include <stdexcept>
-#include "c/util/crypto.h"
-#include "c/encoding/binary-xml-data.h"
-#include "encoding/binary-xml-encoder.hpp"
+#include "../c/util/crypto.h"
+#include "../c/encoding/binary-xml-data.h"
+#include "../encoding/binary-xml-encoder.hpp"
 #include "key-chain.hpp"
 
 using namespace std;
diff --git a/ndn-cpp/key-chain.hpp b/ndn-cpp/security/key-chain.hpp
similarity index 98%
rename from ndn-cpp/key-chain.hpp
rename to ndn-cpp/security/key-chain.hpp
index cc15882..662e6a4 100644
--- a/ndn-cpp/key-chain.hpp
+++ b/ndn-cpp/security/key-chain.hpp
@@ -6,7 +6,7 @@
 #ifndef NDN_KEY_CHAIN_HPP
 #define NDN_KEY_CHAIN_HPP
 
-#include "data.hpp"
+#include "../data.hpp"
 
 namespace ndn {