security: Change to use IdentityCertificate instead of Certificate where needed.
diff --git a/include/ndn-cpp/security/identity/identity-storage.hpp b/include/ndn-cpp/security/identity/identity-storage.hpp
index db6ab0e..d514dc8 100644
--- a/include/ndn-cpp/security/identity/identity-storage.hpp
+++ b/include/ndn-cpp/security/identity/identity-storage.hpp
@@ -15,6 +15,7 @@
 namespace ndn {
 
 class Certificate;
+class IdentityCertificate;
 class Data;
 
 /**
@@ -117,10 +118,10 @@
 
   /**
    * Add a certificate to the identity storage.
-   * @param certificate The certificate to be added.
+   * @param certificate The certificate to be added.  This makes a copy of the certificate.
    */
   virtual void 
-  addCertificate(const Certificate& certificate) = 0;
+  addCertificate(const IdentityCertificate& certificate) = 0;
 
   /**
    * Get a certificate from the identity storage.