Signed Interest Format

Change-Id: Ic52835977cadb34479508c7817f842bd3330961b
Refs: #4599
diff --git a/interest.rst b/interest.rst
index f93185e..0206e6d 100644
--- a/interest.rst
+++ b/interest.rst
@@ -15,13 +15,17 @@
                    Nonce?
                    InterestLifetime?
                    HopLimit?
-                   ApplicationParameters?
+                   (ApplicationParameters |
+                    ApplicationParameters InterestSignatureInfo InterestSignatureValue)?
 
 ``Name`` is the only required element in an Interest packet.
 ``Nonce`` is required when an Interest is transmitted over the network links, i.e., a compliant forwarder must augment the Interest with the ``Nonce`` element if it is missing.
 ``CanBePrefix``, ``MustBeFresh``, ``InterestLifetime``, and ``ForwardingHint`` are optional elements to guide Interest matching or forwarding.
 Interest can also include an optional ``ApplicationParameters`` element.
 
+If an Interest contains ``InterestSignatureInfo`` and ``InterestSignatureValue``, it is considered a Signed Interest.
+See :doc:`Signed Interest section <signed-interest>` for details.
+
 As recommended by :ref:`TLV evolvability guidelines <evolvability>`, unrecognized non-critical TLV elements may appear in the Interest packet.
 However, they must not appear before the ``Name`` element.
 
@@ -133,4 +137,4 @@
                                BYTE*
 
 The ``ApplicationParameters`` element can carry any arbitrary data that parameterizes the request for Data.
-The Interest's name MUST include a Interest parameters digest component to ensure uniqueness and integrity of the parameterized Interest (see :ref:`Interest Parameters Digest Component` section for additional details).
+The Interest's name MUST include a Interest parameters digest component to ensure uniqueness and integrity of the parameterized Interest (see :ref:`Interest Parameters Digest Component` section for additional details).
\ No newline at end of file