security: change enum to enum class in security-common.hpp

Change-Id: I5565c845cd57f3457c8120b11399a105fa83418d
Refs: #3083
diff --git a/src/security/key-params.hpp b/src/security/key-params.hpp
index a82ace0..9769270 100644
--- a/src/security/key-params.hpp
+++ b/src/security/key-params.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2015 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).
  *
@@ -75,7 +75,7 @@
   static KeyType
   getType()
   {
-    return KEY_TYPE_RSA;
+    return KeyType::RSA;
   }
 
   /// @brief check if size is qualified, otherwise return the default key size.
@@ -93,7 +93,7 @@
   static KeyType
   getType()
   {
-    return KEY_TYPE_ECDSA;
+    return KeyType::EC;
   }
 
   /// @brief check if size is qualified, otherwise return the default key size.
@@ -168,7 +168,7 @@
   static KeyType
   getType()
   {
-    return KEY_TYPE_AES;
+    return KeyType::AES;
   }
 
   /// @brief check if size is qualified, otherwise return the default key size.