add EncryptionTLV Encoding and Decoding

Change-Id: I67f6f733e0a02b894e49155167600963c3b2964e
diff --git a/src/ndncert-common.hpp b/src/ndncert-common.hpp
index b9ca5fb..ce43640 100644
--- a/src/ndncert-common.hpp
+++ b/src/ndncert-common.hpp
@@ -97,7 +97,8 @@
   tlv_remaining_time = 167,
   tlv_issued_cert_name = 169,
   tlv_error_code = 171,
-  tlv_error_info = 173
+  tlv_error_info = 173,
+  tlv_authentication_tag = 175
 };
 
 // Parse CA Configuration file