Added a default constructor.
diff --git a/ndn-cpp/util/signed-blob.hpp b/ndn-cpp/util/signed-blob.hpp
index 86b3da0..25966b6 100644
--- a/ndn-cpp/util/signed-blob.hpp
+++ b/ndn-cpp/util/signed-blob.hpp
@@ -19,6 +19,14 @@
class SignedBlob : public Blob {
public:
/**
+ * Create a new SignedBlob with a null pointer.
+ */
+ SignedBlob()
+ : signedPortionBeginOffset_(0), signedPortionEndOffset_(0)
+ {
+ }
+
+ /**
* Create a new SignedBlob with an immutable copy of the given array.
* @param value A pointer to the byte array which is copied.
* @param valueLength The length of value.