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Tink is a small cryptographic library that provides a safe, simple, agile and fast way to accomplish some common cryptographic tasks.

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// 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.
//
////////////////////////////////////////////////////////////////////////////////

package com.google.crypto.tink.mac;

import com.google.crypto.tink.Key;
import com.google.crypto.tink.util.Bytes;

/** Represents functions to compute and verify a cryptographic MAC. */
public abstract class MacKey extends Key {
  /**
   * Returns a {@link Bytes} instance which is prefixed to every mac tag.
   *
   * In order to make key rotation more efficient, Tink allows every Mac key to be prefixed with
   * a sequence of bytes. When verifying a tag, only keys with 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 the other). To avoid this,
   * built in Tink keys use the convention that the prefix is either '0x00' or
   * '0x01'. See the Tink keys for details.
   */
  public abstract Bytes getOutputPrefix();
  /** Returns the parameters of this key. */
  @Override
  public abstract MacParameters getParameters();
}