cc/mac/mac_key.h

// Copyright 2022 Google LLC
//
// 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_MAC_MAC_KEY_H_
#define TINK_MAC_MAC_KEY_H_

#include <string>

#include "tink/key.h"
#include "tink/mac/mac_parameters.h"
#include "tink/util/statusor.h"

namespace crypto {
namespace tink {

// Represents a function to compute/verify a message authentication code (MAC).
class MacKey : public Key {
 public:
  // Returns the bytes prefixed to every MAC tag generated by this key.
  //
  // In order to make key rotation more efficient, Tink allows every MAC key to
  // have an associated tag output prefix.  When verifying a tag, only keys with
  // a matching prefix have to be tried.
  //
  // Note that a priori, the output prefix may not be unique in a keyset
  // (i.e., different keys in a keyset may have the same prefix or one prefix
  // may be a prefix of another). To avoid this, built-in Tink keys use the
  // convention that the prefix is either '0x00<big endian key id>' or
  // '0x01<big endian key id>'.
  virtual absl::string_view GetOutputPrefix() const = 0;

  const MacParameters& GetParameters() const override = 0;

  bool operator==(const Key& other) const override = 0;
};

}  // namespace tink
}  // namespace crypto


#endif  // TINK_MAC_MAC_KEY_H_