diff --git a/src/error-code.hpp b/src/error-code.hpp
new file mode 100644
index 0000000..3e5d2a6
--- /dev/null
+++ b/src/error-code.hpp
@@ -0,0 +1,43 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2015,  Regents of the University of California
+ *
+ * This file is part of ndn-group-encrypt (Group-based Encryption Protocol for NDN).
+ * See AUTHORS.md for complete list of ndn-group-encrypt authors and contributors.
+ *
+ * ndn-group-encrypt is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-group-encrypt 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * ndn-group-encrypt, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @author Yingdi Yu <yingdi@cs.ucla.edu>
+ */
+
+#ifndef NDN_GEP_ERROR_CODE_HPP
+#define NDN_GEP_ERROR_CODE_HPP
+
+#include "common.hpp"
+
+namespace ndn {
+namespace gep {
+
+enum class ErrorCode {
+  Timeout = 1,
+  Validation = 2,
+  UnsupportedEncryptionScheme = 32,
+  InvalidEncryptedFormat = 33,
+  NoDecryptKey = 34
+};
+
+typedef function<void (const ErrorCode&, const std::string&)> ErrorCallBack;
+
+} // namespace gep
+} // namespace ndn
+
+#endif // NDN_GEP_ERROR_CODE_HPP