security: Adding supports to signed interest

refs: #1161

Change-Id: I042381b171d44417f296397d872cd639935a89e9
diff --git a/src/encoding/block.hpp b/src/encoding/block.hpp
index a764dd1..9c2777d 100644
--- a/src/encoding/block.hpp
+++ b/src/encoding/block.hpp
@@ -184,6 +184,9 @@
   inline size_t
   value_size() const;
 
+  Block
+  blockFromValue() const;
+
 protected:
   ConstBufferPtr m_buffer;