security: Add signing/verification support in transformation

Change-Id: I6364fa0e1ebcc7cc932b401eb50fc56251ea8c84
Refs: #3009
diff --git a/src/security/transform/verifier-filter.hpp b/src/security/transform/verifier-filter.hpp
new file mode 100644
index 0000000..ee69f03
--- /dev/null
+++ b/src/security/transform/verifier-filter.hpp
@@ -0,0 +1,73 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2016 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#ifndef NDN_CXX_SECURITY_TRANSFORM_VERIFIER_FILTER_HPP
+#define NDN_CXX_SECURITY_TRANSFORM_VERIFIER_FILTER_HPP
+
+#include "transform-base.hpp"
+#include "public-key.hpp"
+#include "../security-common.hpp"
+
+namespace ndn {
+namespace security {
+namespace transform {
+
+/**
+ * @brief The module to verify signature.
+ *
+ * The next module is usually SinkBool.
+ */
+class VerifierFilter : public Transform
+{
+public:
+  /**
+   * @brief Create a verifier module to verify signature @p sig using algorithm @p algo and @p key
+   */
+  VerifierFilter(DigestAlgorithm algo, const PublicKey& key, const uint8_t* sig, size_t sigLen);
+
+private:
+  /**
+   * @brief Write data @p buf into verifier
+   *
+   * @return The number of bytes that are actually written
+   */
+  virtual size_t
+  convert(const uint8_t* buf, size_t size) final;
+
+  /**
+   * @brief Finalize verification and write the result (single byte) into next module.
+   */
+  virtual void
+  finalize() final;
+
+private:
+  class Impl;
+  unique_ptr<Impl> m_impl;
+};
+
+unique_ptr<Transform>
+verifierFilter(DigestAlgorithm algo, const PublicKey& key, const uint8_t* sig, size_t sigLen);
+
+} // namespace transform
+} // namespace security
+} // namespace ndn
+
+#endif // NDN_CXX_SECURITY_TRANSFORM_VERIFIER_FILTER_HPP