code style: Don't use std:: inside .cpp files.
diff --git a/ndn-cpp/security/certificate/certificate.cpp b/ndn-cpp/security/certificate/certificate.cpp
index 8f6288c..9047a70 100644
--- a/ndn-cpp/security/certificate/certificate.cpp
+++ b/ndn-cpp/security/certificate/certificate.cpp
@@ -102,7 +102,7 @@
 
   root->encode(start);
 
-  shared_ptr<std::vector<uint8_t> > blob = blobStream.buf();
+  shared_ptr<vector<uint8_t> > blob = blobStream.buf();
   setContent(blob);
 }