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

Change-Id: I5565c845cd57f3457c8120b11399a105fa83418d
Refs: #3083
diff --git a/src/security/certificate.cpp b/src/security/certificate.cpp
index 02916a9..1b004ed 100644
--- a/src/security/certificate.cpp
+++ b/src/security/certificate.cpp
@@ -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).
  *
@@ -284,10 +284,10 @@
 
   os << "Public key bits: ";
   switch (m_key.getKeyType()) {
-  case KEY_TYPE_RSA:
+  case KeyType::RSA:
     os << "(RSA)";
     break;
-  case KEY_TYPE_ECDSA:
+  case KeyType::EC:
     os << "(ECDSA)";
     break;
   default: