diff --git a/ndn-cpp/c/encoding/binary-xml-data.h b/ndn-cpp/c/encoding/binary-xml-data.h
index 32c0cfb..df77d69 100644
--- a/ndn-cpp/c/encoding/binary-xml-data.h
+++ b/ndn-cpp/c/encoding/binary-xml-data.h
@@ -15,7 +15,18 @@
 extern "C" {
 #endif
 
-ndn_Error ndn_encodeBinaryXmlData(struct ndn_Data *data, struct ndn_BinaryXmlEncoder *encoder);
+/**
+ * Encode the data as binary XML.
+ * @param data Pointer to the data object the encode.
+ * @param signedFieldsBeginOffset Return the offset in the encoding of the beginning of the fields which are signed.
+ * If you are not encoding in order to sign, you can ignore this.
+ * @param signedFieldsEndOffset Return the offset in the encoding of the end of the fields which are signed.
+ * If you are not encoding in order to sign, you can ignore this.
+ * @param encoder Pointer to the encoder object which receives the encoding. 
+ * @return 
+ */
+ndn_Error ndn_encodeBinaryXmlData
+  (struct ndn_Data *data, unsigned int *signedFieldsBeginOffset, unsigned int *signedFieldsEndOffset, struct ndn_BinaryXmlEncoder *encoder);
 
 ndn_Error ndn_decodeBinaryXmlData(struct ndn_Data *data, struct ndn_BinaryXmlDecoder *decoder);