content: /*
   * Copyright (C) 2018 The Android Open Source Project
   *
   * 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.android.server.backup.encryption.keys;
  
  import java.security.NoSuchAlgorithmException;
  import java.security.SecureRandom;
  
  import javax.crypto.KeyGenerator;
  import javax.crypto.SecretKey;
  
  /** 256-bit AES key generator. Each app should have its own separate AES key. */
  public class TertiaryKeyGenerator {
      private static final int KEY_SIZE_BITS = 256;
      private static final String KEY_ALGORITHM = "AES";
  
      private final KeyGenerator mKeyGenerator;
  
      /** New instance generating keys using {@code secureRandom}. */
      public TertiaryKeyGenerator(SecureRandom secureRandom) {
          try {
              mKeyGenerator = KeyGenerator.getInstance(KEY_ALGORITHM);
              mKeyGenerator.init(KEY_SIZE_BITS, secureRandom);
          } catch (NoSuchAlgorithmException e) {
              throw new RuntimeException(
                      "Impossible condition: JCE thinks it does not support AES.", e);
          }
      }
  
      /** Generates a new random AES key. */
      public SecretKey generate() {
          return mKeyGenerator.generateKey();
      }
  }
  