signature: Defining KeyLocator as an optional field in generic SignatureInfo

Change-Id: I2e2850bdf5b1795c07aea208fe8c80c8b6df509f
diff --git a/interest.rst b/interest.rst
index 35b54ae..4329242 100644
--- a/interest.rst
+++ b/interest.rst
@@ -141,7 +141,7 @@
 
     Nonce ::= NONCE-TYPE TLV-LENGTH(=4) BYTE{4}
 
-The Nonce carries a randomly-genenerated 4-octet long byte-string.
+The Nonce carries a randomly-generated 4-octet long byte-string.
 The combination of Name and Nonce should uniquely identify an Interest packet.
 This is used to detect looping Interests.