diff --git a/ndn-cpp/security/key-chain.cpp b/ndn-cpp/security/key-chain.cpp
index 5ba46ba..ba36071 100644
--- a/ndn-cpp/security/key-chain.cpp
+++ b/ndn-cpp/security/key-chain.cpp
@@ -67,9 +67,9 @@
 static void digestDataFieldsSha256(const Data& data, WireFormat& wireFormat, unsigned char *digest)
 {
   unsigned int signedFieldsBeginOffset, signedFieldsEndOffset;
-  ptr_lib::shared_ptr<vector<unsigned char> > encoding = wireFormat.encodeData(data, &signedFieldsBeginOffset, &signedFieldsEndOffset);
+  Blob encoding = wireFormat.encodeData(data, &signedFieldsBeginOffset, &signedFieldsEndOffset);
   
-  ndn_digestSha256(&encoding->front() + signedFieldsBeginOffset, signedFieldsEndOffset - signedFieldsBeginOffset, digest);
+  ndn_digestSha256(encoding.buf() + signedFieldsBeginOffset, signedFieldsEndOffset - signedFieldsBeginOffset, digest);
 }
 
 void KeyChain::sign