Make Signature an abstract base class and added subclass Sha256WithRsaSignature. Change Data.signature to a pointer to a Signature.
diff --git a/Makefile.am b/Makefile.am
index 7cf4e84..3cbea55 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -54,6 +54,7 @@
   ndn-cpp/name.cpp ndn-cpp/c/name.h ndn-cpp/name.hpp \
   ndn-cpp/node.cpp ndn-cpp/node.hpp \
   ndn-cpp/publisher-public-key-digest.hpp \
+  ndn-cpp/sha256-woth-rsa-signature.cpp ndn-cpp/sha256-woth-rsa-signature.hpp \
   ndn-cpp/c/encoding/binary-xml.h \
   ndn-cpp/c/encoding/binary-xml-decoder.h ndn-cpp/encoding/binary-xml-decoder.hpp \
   ndn-cpp/c/encoding/binary-xml-element-reader.h ndn-cpp/encoding/binary-xml-element-reader.cpp ndn-cpp/encoding/binary-xml-element-reader.hpp \