security: Bug fixing

1. correct the error message for non-existing public key.
2. rename private key export/import methods to avoid confusion.

Refs: #1527

Change-Id: I3ea8378378a66e1fbec7f0d4f210057c8f9b969b
diff --git a/src/security/sec-tpm-file.hpp b/src/security/sec-tpm-file.hpp
index 8cc20df..4dbbf79 100644
--- a/src/security/sec-tpm-file.hpp
+++ b/src/security/sec-tpm-file.hpp
@@ -107,10 +107,10 @@
    * From TrustedPlatformModule *
    ******************************/
   virtual ConstBufferPtr
-  exportPrivateKeyPkcs1FromTpm(const Name& keyName);
+  exportPrivateKeyPkcs8FromTpm(const Name& keyName);
 
   virtual bool
-  importPrivateKeyPkcs1IntoTpm(const Name& keyName, const uint8_t* buf, size_t size);
+  importPrivateKeyPkcs8IntoTpm(const Name& keyName, const uint8_t* buf, size_t size);
 
   virtual bool
   importPublicKeyPkcs1IntoTpm(const Name& keyName, const uint8_t* buf, size_t size);