security: Change to use IdentityCertificate instead of Certificate where needed.
diff --git a/include/ndn-cpp/security/certificate/certificate.hpp b/include/ndn-cpp/security/certificate/certificate.hpp
index 29626b3..0fdd213 100644
--- a/include/ndn-cpp/security/certificate/certificate.hpp
+++ b/include/ndn-cpp/security/certificate/certificate.hpp
@@ -14,7 +14,17 @@
 namespace ndn {
 
 class Certificate : public Data {
-  
+public:
+  /**
+   * The default constructor.
+   */
+  Certificate();
+
+  /**
+   * Create a Certificate from the content in the data packet.
+   * @param data The data packet with the content to decode.
+   */
+  Certificate(const Data& data);
 };
 
 }
diff --git a/include/ndn-cpp/security/certificate/identity-certificate.hpp b/include/ndn-cpp/security/certificate/identity-certificate.hpp
index 4d68231..41035a7 100644
--- a/include/ndn-cpp/security/certificate/identity-certificate.hpp
+++ b/include/ndn-cpp/security/certificate/identity-certificate.hpp
@@ -1,6 +1,7 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
 /**
  * Copyright (C) 2013 Regents of the University of California.
+ * @author: Yingdi Yu <yingdi@cs.ucla.edu>
  * @author: Jeff Thompson <jefft0@remap.ucla.edu>
  * See COPYING for copyright and distribution information.
  */
@@ -14,7 +15,17 @@
 
 class IdentityCertificate : public Certificate
 {
+public:
+  /**
+   * The default constructor.
+   */
+  IdentityCertificate();
 
+  /**
+   * Create an IdentityCertificate from the content in the data packet.
+   * @param data The data packet with the content to decode.
+   */
+  IdentityCertificate(const Data& data);
 };
 
 }