diff --git a/include/ndn-cpp/security/verifier.hpp b/include/ndn-cpp/security/verifier.hpp
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@@ -0,0 +1,95 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/**
+ * Copyright (C) 2013 Regents of the University of California.
+ * @author: Yingdi Yu <yingdi@cs.ucla.edu>
+ * @author: Jeff Thompson <jefft0@remap.ucla.edu>
+ * See COPYING for copyright and distribution information.
+ */
+
+#ifndef NDN_VERIFIER_HPP
+#define NDN_VERIFIER_HPP
+
+#include "../data.hpp"
+#include "../face.hpp"
+#include "policy/validation-request.hpp"
+#include "certificate/public-key.hpp"
+#include "signature/signature-sha256-with-rsa.hpp"
+
+namespace ndn {
+
+class PolicyManager;
+  
+/**
+ * Verifier is one of the main classes of the security librar .
+ *
+ * The Verifier class provides the interfaces for packet verification.
+ */
+class Verifier {
+public:
+  struct Error : public std::runtime_error { Error(const std::string &what) : std::runtime_error(what) {} };
+
+  Verifier(const ptr_lib::shared_ptr<PolicyManager> &policyManager = DefaultPolicyManager);
+
+  /**
+   * @brief Set the Face which will be used to fetch required certificates.
+   * @param face A pointer to the Face object.
+   *
+   * Setting face is necessary for verifier operation that involve fetching data.
+   */
+  void
+  setFace(const ptr_lib::shared_ptr<Face> &face) { face_ = face; }
+  
+  /**
+   * @brief Get the policyManager.
+   * @return The PolicyManager.
+   */
+  inline PolicyManager&
+  policies()
+  {
+    if (!policyManager_)
+      throw Error("PolicyManager is not assigned to the KeyChain");
+
+    return *policyManager_;
+  }
+
+
+  /**
+   * Check the signature on the Data object and call either onVerify or onVerifyFailed. 
+   * We use callback functions because verify may fetch information to check the signature.
+   * @param data The Data object with the signature to check. It is an error if data does not have a wireEncoding. 
+   * To set the wireEncoding, you can call data.wireDecode.
+   * @param onVerified If the signature is verified, this calls onVerified(data).
+   * @param onVerifyFailed If the signature check fails, this calls onVerifyFailed(data).
+   */
+  void
+  verifyData
+    (const ptr_lib::shared_ptr<Data>& data, const OnVerified& onVerified, const OnVerifyFailed& onVerifyFailed, int stepCount = 0);
+
+  /*****************************************
+   *      verifySignature method set       *
+   *****************************************/
+  static bool
+  verifySignature(const Data& data, const SignatureSha256WithRsa& sig, const PublicKey& publicKey);
+
+
+public:
+  static const ptr_lib::shared_ptr<PolicyManager>     DefaultPolicyManager;
+    
+private:
+  void
+  onCertificateData
+    (const ptr_lib::shared_ptr<const Interest> &interest, const ptr_lib::shared_ptr<Data> &data, ptr_lib::shared_ptr<ValidationRequest> nextStep);
+  
+  void
+  onCertificateInterestTimeout
+    (const ptr_lib::shared_ptr<const Interest> &interest, int retry, const OnVerifyFailed& onVerifyFailed, 
+     const ptr_lib::shared_ptr<Data> &data, ptr_lib::shared_ptr<ValidationRequest> nextStep);
+
+private:
+  ptr_lib::shared_ptr<PolicyManager>     policyManager_;
+  ptr_lib::shared_ptr<Face>        face_;
+};
+
+}
+
+#endif