security: Add new v2::KeyChain

Change-Id: I5fdf51ecd96b50db2a7cbf730c6e8b1d9fbe09e9
Refs: #2926
diff --git a/src/security/tpm/back-end-file.cpp b/src/security/tpm/back-end-file.cpp
index f16d7cf..1adcf1c 100644
--- a/src/security/tpm/back-end-file.cpp
+++ b/src/security/tpm/back-end-file.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).
  *
@@ -83,6 +83,13 @@
 
 BackEndFile::~BackEndFile() = default;
 
+const std::string&
+BackEndFile::getScheme()
+{
+  static std::string scheme = "tpm-file";
+  return scheme;
+}
+
 bool
 BackEndFile::doHasKey(const Name& keyName) const
 {