add encryption (#1002)

* add encryption

* add doc

* add doc

* fix bug

fastdeploy/encryption/include/encrypt.h

@@ -0,0 +1,58 @@
+// 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 <iostream>
+#include <string>
+
+#include "fastdeploy/utils/utils.h"
+
+#ifndef PADDLE_MODEL_PROTECT_API_PADDLE_MODEL_ENCRYPT_H
+#define PADDLE_MODEL_PROTECT_API_PADDLE_MODEL_ENCRYPT_H
+namespace fastdeploy {
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** \brief generate a random key(base64-32bytes) for an encrypted model
+ *
+ * \return std::string key
+ */
+FASTDEPLOY_DECL std::string GenerateRandomKey();
+
+/** \brief encrypt a std::istream with key
+ *
+ * \param[in] keydata The key(base64-32bytes) for encryption
+ * \param[in] in_stream The plain stream
+ * \param[in] out_stream The ecrypted stream
+ * \return true if encrypt successed, otherwise false
+ */
+FASTDEPLOY_DECL int EncryptStream(const std::string &keydata,
+                                 std::istream& in_stream,
+                                 std::ostream& out_stream);
+
+/** \brief encrypt a string with key
+ *
+ * \param[in] input The input string for encryption
+ * \param[in] key If not given by user, generate key automatically.
+ * \return std::vector<std::string> [encrypted string, key]
+ */
+FASTDEPLOY_DECL std::vector<std::string> Encrypt(const std::string& input,
+                  const std::string& key = GenerateRandomKey());
+
+#ifdef __cplusplus
+}
+#endif
+}  // namespace fastdeploy
+#endif  // PADDLE_MODEL_PROTECT_API_PADDLE_MODEL_ENCRYPT_H