security: code cleanup and doxygen improvements in tpm::BackEndOsx

Change-Id: I6d6d77ab315a10c280e7643d4cec5269ed10fe5e
diff --git a/src/security/tpm/back-end-osx.hpp b/src/security/tpm/back-end-osx.hpp
index bb018be..0a7ba27 100644
--- a/src/security/tpm/back-end-osx.hpp
+++ b/src/security/tpm/back-end-osx.hpp
@@ -23,12 +23,13 @@
 #define NDN_SECURITY_TPM_BACK_END_OSX_HPP
 
 #include "back-end.hpp"
-#include "key-ref-osx.hpp"
 
 #ifndef NDN_CXX_HAVE_OSX_FRAMEWORKS
 #error "This file should not be compiled ..."
 #endif
 
+#include "key-ref-osx.hpp"
+
 namespace ndn {
 namespace security {
 namespace tpm {
@@ -36,17 +37,18 @@
 /**
  * @brief The back-end implementation of TPM based on macOS Keychain Services.
  */
-class BackEndOsx : public BackEnd
+class BackEndOsx final : public BackEnd
 {
 public:
   /**
-   * @brief Create TPM backed based on macOS KeyChain service
-   * @param location Not used (required by the TPM-registration interface)
+   * @brief Create TPM backed based on macOS Keychain Services.
+   *
+   * @param location Not used (required by the TPM registration interface).
    */
   explicit
   BackEndOsx(const std::string& location = "");
 
-  ~BackEndOsx() override;
+  ~BackEndOsx() final;
 
   static const std::string&
   getScheme();
@@ -78,54 +80,21 @@
   derivePublicKey(const KeyRefOsx& key);
 
 private: // inherited from tpm::BackEnd
-  /**
-   * @return True if a key with name @p keyName exists in TPM.
-   */
   bool
   doHasKey(const Name& keyName) const final;
 
-  /**
-   * @return The handle of a key with name @p keyName, or nullptr if the key does not exist
-   */
   unique_ptr<KeyHandle>
   doGetKeyHandle(const Name& keyName) const final;
 
-  /**
-   * @brief Create key for @p identityName according to @p params.
-   *
-   * The created key is named as: /<identityName>/[keyId]/KEY
-   * The key name is set in the returned KeyHandle.
-   *
-   * @return The handle of the created key.
-   */
   unique_ptr<KeyHandle>
   doCreateKey(const Name& identityName, const KeyParams& params) final;
 
-  /**
-   * @brief Delete a key with name @p keyName.
-   *
-   * @throw Error the deletion failed
-   */
   void
   doDeleteKey(const Name& keyName) final;
 
-  /**
-   * @return A private key with name @p keyName in encrypted PKCS #8 format using password @p pw
-   * @throw Error the key cannot be exported, e.g., not enough privilege
-   */
   ConstBufferPtr
   doExportKey(const Name& keyName, const char* pw, size_t pwLen) final;
 
-  /**
-   * @brief Import a private key in encrypted PKCS #8 format
-   *
-   * @param keyName The name of imported private key
-   * @param buf Pointer to the key in encrypted PKCS #8 format
-   * @param size The size of the key in encrypted PKCS #8 format
-   * @param pw The password to decrypt the private key
-   * @param pwLen The length of the password
-   * @throw Error import fails
-   */
   void
   doImportKey(const Name& keyName, const uint8_t* buf, size_t size, const char* pw, size_t pwLen) final;