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// Copyright 2018 Google Inc.
//
// 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.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef TINK_SUBTLE_AES_GCM_SIV_BORINGSSL_H_
#define TINK_SUBTLE_AES_GCM_SIV_BORINGSSL_H_
#include <memory>
#include "absl/strings/string_view.h"
#include "openssl/aead.h"
#include "tink/aead.h"
#include "tink/util/status.h"
#include "tink/util/statusor.h"
namespace crypto {
namespace tink {
namespace subtle {
// AES-GCM-SIV is based on the paper
// “GCM-SIV: full nonce misuse-resistant authenticated encryption at under one
// cycle per byte.” by S.Gueron, and Y.Lindell,
// Proceedings of the 22nd ACM SIGSAC Conference on Computer and Communications
// Security. ACM, 2015.
// The implementation uses AES-GCM-SIV as defined in draft-irtf-cfrg-gcmsiv-08
// https://datatracker.ietf.org/doc/draft-irtf-cfrg-gcmsiv/
//
// This encryption mode is intended for authenticated encryption with
// additional authenticated data. A major security problem with AES-GCM is
// that reusing the same nonce twice leaks the authentication key.
// AES-GCM-SIV on the other hand has been designed to avoid this vulnerability.
//
// Usage bounds for the encryption mode can be found on
// https://cyber.biu.ac.il/aes-gcm-siv/
// or Section 6.3 of this paper:
// https://eprint.iacr.org/2017/702.pdf
class AesGcmSivBoringSsl : public Aead {
public:
static crypto::tink::util::StatusOr<std::unique_ptr<Aead>> New(
absl::string_view key_value);
crypto::tink::util::StatusOr<std::string> Encrypt(
absl::string_view plaintext,
absl::string_view additional_data) const override;
crypto::tink::util::StatusOr<std::string> Decrypt(
absl::string_view ciphertext,
absl::string_view additional_data) const override;
~AesGcmSivBoringSsl() override {}
private:
static const int IV_SIZE_IN_BYTES = 12;
static const int TAG_SIZE_IN_BYTES = 16;
AesGcmSivBoringSsl() {}
crypto::tink::util::Status Init(absl::string_view key_value);
bssl::ScopedEVP_AEAD_CTX ctx_;
};
} // namespace subtle
} // namespace tink
} // namespace crypto
#endif // TINK_SUBTLE_AES_GCM_SIV_BORINGSSL_H_