signature: Defining KeyLocator as an optional field in generic SignatureInfo

Change-Id: I2e2850bdf5b1795c07aea208fe8c80c8b6df509f
diff --git a/changelog.rst b/changelog.rst
index fac1e35..f35ed3a 100644
--- a/changelog.rst
+++ b/changelog.rst
@@ -6,8 +6,10 @@
 
 - **Signature**
 
-  + New ``SignatureSha256WithEcdsa`` signature type for Elliptic Curve Digital Signature Algorithm (ECDSA)
+  + New ``SignatureSha256WithEcdsa`` signature type for Elliptic Curve Digital Signature Algorithm (ECDSA).
   + ``KeyLocatorDigest`` renamed to ``KeyDigest``.  The specification now explicitly allows KeyDigest to be a SHA256 of any type of the key.
+  + ``KeyLocator`` field is now defined to be optionally present in generic ``SignatureInfo`` block.
+    ``SignatureSha256WithRsa`` and ``SignatureSha256WithEcdsa`` still require ``KeyLocator`` to be always present.
 
 Since CCNx 0.7.2
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