diff --git a/src/security/tpm/back-end-osx.cpp b/src/security/tpm/back-end-osx.cpp
index 53c2295..145ffeb 100644
--- a/src/security/tpm/back-end-osx.cpp
+++ b/src/security/tpm/back-end-osx.cpp
@@ -1,5 +1,5 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
+/*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
@@ -100,7 +100,10 @@
 getDigestAlgorithm(DigestAlgorithm digestAlgo)
 {
   switch (digestAlgo) {
+  case DigestAlgorithm::SHA224:
   case DigestAlgorithm::SHA256:
+  case DigestAlgorithm::SHA384:
+  case DigestAlgorithm::SHA512:
     return kSecDigestSHA2;
   default:
     return 0;
@@ -111,15 +114,21 @@
 getDigestSize(DigestAlgorithm digestAlgo)
 {
   switch (digestAlgo) {
+  case DigestAlgorithm::SHA224:
+    return 224;
   case DigestAlgorithm::SHA256:
     return 256;
+  case DigestAlgorithm::SHA384:
+    return 384;
+  case DigestAlgorithm::SHA512:
+    return 512;
   default:
     return -1;
   }
 }
 
 BackEndOsx::BackEndOsx(const std::string&)
-  : m_impl(new Impl)
+  : m_impl(make_unique<Impl>())
 {
   SecKeychainSetUserInteractionAllowed(!m_impl->isTerminalMode);
 
diff --git a/src/security/tpm/key-handle-mem.cpp b/src/security/tpm/key-handle-mem.cpp
index 00f5b21..d9b5c32 100644
--- a/src/security/tpm/key-handle-mem.cpp
+++ b/src/security/tpm/key-handle-mem.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2016 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -20,9 +20,9 @@
  */
 
 #include "key-handle-mem.hpp"
-#include "../../encoding/buffer-stream.hpp"
 #include "../transform.hpp"
 #include "../transform/private-key.hpp"
+#include "../../encoding/buffer-stream.hpp"
 
 namespace ndn {
 namespace security {
@@ -39,17 +39,11 @@
 ConstBufferPtr
 KeyHandleMem::doSign(DigestAlgorithm digestAlgorithm, const uint8_t* buf, size_t size) const
 {
-  switch (digestAlgorithm) {
-    case DigestAlgorithm::SHA256: {
-      using namespace transform;
+  using namespace transform;
 
-      OBufferStream sigOs;
-      bufferSource(buf, size) >> signerFilter(digestAlgorithm, *m_key) >> streamSink(sigOs);
-      return sigOs.buf();
-    }
-    default:
-      return nullptr;
-  }
+  OBufferStream sigOs;
+  bufferSource(buf, size) >> signerFilter(digestAlgorithm, *m_key) >> streamSink(sigOs);
+  return sigOs.buf();
 }
 
 ConstBufferPtr