diff --git a/src/security/v2/validation-error.cpp b/src/security/v2/validation-error.cpp
new file mode 100644
index 0000000..5868a6d
--- /dev/null
+++ b/src/security/v2/validation-error.cpp
@@ -0,0 +1,79 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2017 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.
+ */
+
+#include "validation-error.hpp"
+
+#include <ostream>
+
+namespace ndn {
+namespace security {
+namespace v2 {
+
+std::ostream&
+operator<<(std::ostream& os, ValidationError::Code code)
+{
+  switch (code) {
+    case ValidationError::Code::NO_ERROR:
+      return os << "No error";
+    case ValidationError::Code::INVALID_SIGNATURE:
+      return os << "Invalid signature";
+    case ValidationError::Code::NO_SIGNATURE:
+      return os << "Missing signature";
+    case ValidationError::Code::CANNOT_RETRIEVE_CERT:
+      return os << "Cannot retrieve certificate";
+    case ValidationError::Code::EXPIRED_CERT:
+      return os << "Certificate expired";
+    case ValidationError::Code::LOOP_DETECTED:
+      return os << "Loop detected in certification chain";
+    case ValidationError::Code::MALFORMED_CERT:
+      return os << "Malformed certificate";
+    case ValidationError::Code::EXCEEDED_DEPTH_LIMIT:
+      return os << "Exceeded validation depth limit";
+    case ValidationError::Code::INVALID_KEY_LOCATOR:
+      return os << "Key locator violates validation policy";
+    case ValidationError::Code::POLICY_ERROR:
+      return os << "Validation policy error";
+    case ValidationError::Code::IMPLEMENTATION_ERROR:
+      return os << "Internal implementation error";
+    case ValidationError::Code::USER_MIN:
+      break;
+  }
+  if (code >= ValidationError::Code::USER_MIN) {
+    return os << "Custom error code " << static_cast<uint32_t>(code);
+  }
+  else {
+    return os << "Unrecognized error code " << static_cast<uint32_t>(code);
+  }
+}
+
+std::ostream&
+operator<<(std::ostream& os, const ValidationError& error)
+{
+  os << static_cast<ValidationError::Code>(error.getCode());
+  if (!error.getInfo().empty()) {
+    os << " (" << error.getInfo() << ")";
+  }
+  return os;
+}
+
+} // namespace v2
+} // namespace security
+} // namespace ndn