security: rename SignatureSha256 to DigestSha256

Change-Id: Idabb95222d86e2541372593698ed9754156a5df2
diff --git a/src/security/key-chain.hpp b/src/security/key-chain.hpp
index 00a2e6b..191eeda 100644
--- a/src/security/key-chain.hpp
+++ b/src/security/key-chain.hpp
@@ -28,7 +28,7 @@
 #include "sec-tpm.hpp"
 #include "secured-bag.hpp"
 #include "signature-sha256-with-rsa.hpp"
-#include "signature-sha256.hpp"
+#include "digest-sha256.hpp"
 
 #include "../interest.hpp"
 #include "../util/crypto.hpp"
@@ -808,7 +808,7 @@
 inline void
 KeyChain::signWithSha256(Data& data)
 {
-  SignatureSha256 sig;
+  DigestSha256 sig;
   data.setSignature(sig);
 
   Block sigValue(Tlv::SignatureValue,