add encryption (#1002)

* add encryption

* add doc

* add doc

* fix bug

fastdeploy/encryption/util/include/system_utils.h

@@ -0,0 +1,42 @@
+// Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#pragma once
+
+#include <string>
+#include <vector>
+
+#ifndef PADDLE_MODEL_PROTECT_SYSTEM_UTIL_H
+#define PADDLE_MODEL_PROTECT_SYSTEM_UTIL_H
+namespace fastdeploy {
+namespace util {
+
+class SystemUtils {
+ public:
+  static std::string random_key_iv(int len);
+  static std::string random_str(int len);
+  static int check_key_match(const char* key, const char* filepath);
+  static int check_key_match(const std::string& key,
+                             std::istream& cipher_stream);
+  static int check_file_encrypted(const char* filepath);
+  static int check_file_encrypted(std::istream& cipher_stream);
+  static int check_pattern_exist(const std::vector<std::string>& vecs,
+                                 const std::string& pattern);
+
+ private:
+  inline static int intN(int n);
+};
+
+}  // namespace util
+}  // namespace fastdeploy
+#endif  // PADDLE_MODEL_PROTECT_SYSTEM_UTIL_H