add encryption (#1002)

* add encryption

* add doc

* add doc

* fix bug

fastdeploy/encryption/util/include/constant/constant_model.h

@@ -0,0 +1,30 @@
+//   Copyright (c) 2022 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>
+#ifndef PADDLE_MODEL_PROTECT_CONSTANT_CONSTANT_MODEL_H
+#define PADDLE_MODEL_PROTECT_CONSTANT_CONSTANT_MODEL_H
+namespace fastdeploy {
+namespace constant {
+
+const static std::string MAGIC_NUMBER = "PADDLE";  // NOLINT
+const static std::string VERSION = "1";            // NOLINT
+
+const static int MAGIC_NUMBER_LEN = 6;  // NOLINT
+const static int VERSION_LEN = 1;       // NOLINT
+const static int TAG_LEN = 128;         // NOLINT
+
+}  // namespace constant
+}  // namespace fastdeploy
+#endif  // PADDLE_MODEL_PROTECT_CONSTANT_CONSTANT_MODEL_H