Add certificate specification
Imported from the ndn-cxx repo
Change-Id: I96040f854b16219f3be956c9aab9e13568cca900
diff --git a/data.rst b/data.rst
index 16bdabf..50b224c 100644
--- a/data.rst
+++ b/data.rst
@@ -52,7 +52,7 @@
+-----------------+-----------------+--------------------------------------------------------------+
| LINK | 1 | list of delegations (see :ref:`Link`) |
+-----------------+-----------------+--------------------------------------------------------------+
-| KEY | 2 | public key |
+| KEY | 2 | public key (see :ref:`Certificate`) |
+-----------------+-----------------+--------------------------------------------------------------+
| NACK | 3 | application-level NACK |
+-----------------+-----------------+--------------------------------------------------------------+