add encryption (#1002)

* add encryption

* add doc

* add doc

* fix bug

fastdeploy/encryption/util/include/crypto/base64.h

@@ -0,0 +1,33 @@
+// 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 <vector>
+#include <string>
+
+#ifndef PADDLE_MODEL_PROTECT_UTIL_CRYPTO_BASE64_UTILS_H
+#define PADDLE_MODEL_PROTECT_UTIL_CRYPTO_BASE64_UTILS_H
+namespace fastdeploy {
+namespace baidu {
+namespace base {
+namespace base64 {
+
+std::string base64_encode(const std::string& input);
+std::string base64_decode(const std::string& input);
+
+}  // namespace base64
+}  // namespace base
+}  // namespace baidu
+}  // namespace fastdeploy
+#endif  // PADDLE_MODEL_PROTECT_BASE64_UTILS_H