Added separate PublishPublicKeyDigest and use in Interest.
diff --git a/ndn-cpp/c/encoding/BinaryXMLPublisherPublicKeyDigest.c b/ndn-cpp/c/encoding/BinaryXMLPublisherPublicKeyDigest.c
new file mode 100644
index 0000000..b1ee3f8
--- /dev/null
+++ b/ndn-cpp/c/encoding/BinaryXMLPublisherPublicKeyDigest.c
@@ -0,0 +1,35 @@
+/**
+ * @author: Jeff Thompson
+ * Derived from PublisherPublicKeyDigest.js by Meki Cheraoui.
+ * See COPYING for copyright and distribution information.
+ */
+
+#include "BinaryXML.h"
+#include "BinaryXMLPublisherPublicKeyDigest.h"
+
+ndn_Error ndn_encodeBinaryXMLPublisherPublicKeyDigest
+  (struct ndn_PublisherPublicKeyDigest *publisherPublicKeyDigest, struct ndn_BinaryXMLEncoder *encoder)
+{  
+  if (!publisherPublicKeyDigest->publisherPublicKeyDigest || publisherPublicKeyDigest->publisherPublicKeyDigestLength == 0)
+    return;
+  
+  ndn_Error error;
+  if (error = ndn_BinaryXMLEncoder_writeBlobDTagElement
+      (encoder, ndn_BinaryXML_DTag_PublisherPublicKeyDigest, publisherPublicKeyDigest->publisherPublicKeyDigest, 
+       publisherPublicKeyDigest->publisherPublicKeyDigestLength))
+    return error;
+  
+  return 0;
+}
+
+ndn_Error ndn_decodeBinaryXMLPublisherPublicKeyDigest
+  (struct ndn_PublisherPublicKeyDigest *publisherPublicKeyDigest, struct ndn_BinaryXMLDecoder *decoder)
+{
+  ndn_Error error; 
+  if (error = ndn_BinaryXMLDecoder_readBinaryDTagElement
+      (decoder, ndn_BinaryXML_DTag_PublisherPublicKeyDigest, 0, &publisherPublicKeyDigest->publisherPublicKeyDigest,
+       &publisherPublicKeyDigest->publisherPublicKeyDigestLength))
+    return error;
+  
+  return 0;
+}