unify the naming convention in crypto helper

Change-Id: Ibc100f4efa65e4eb61d5b53bad79e16906aa201d
diff --git a/src/ca-module.cpp b/src/ca-module.cpp
index 67b034b..807baf8 100644
--- a/src/ca-module.cpp
+++ b/src/ca-module.cpp
@@ -295,7 +295,7 @@
   uint8_t requestIdData[32];
   Block certNameTlv = clientCert->getName().wireEncode();
   try {
-    hmac_sha256(certNameTlv.wire(), certNameTlv.size(), m_requestIdGenKey, 32, requestIdData);
+    hmacSha256(certNameTlv.wire(), certNameTlv.size(), m_requestIdGenKey, 32, requestIdData);
   }
   catch (const std::runtime_error& e) {
     NDN_LOG_ERROR("Error computing the request ID: " << std::string(e.what()));