content: /*
   * Copyright 2017 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 android.privacy;
  
  /**
   * An interface for differential privacy encoder.
   * Applications can use it to convert privacy sensitive data to privacy protected report.
   * There is no decoder implemented in Android as it is not possible decode a single report by
   * design.
   *
   * <p>Each type of log should have its own encoder, otherwise it may leak
   * some information about Permanent Randomized Response(PRR, is used to create a “noisy”
   * answer which is memoized by the client and permanently reused in place of the real answer).
   *
   * <p>Some encoders may not support all encoding methods, and it will throw {@link
   * UnsupportedOperationException} if you call unsupported encoding method.
   *
   * <p><b>WARNING:</b> Privacy protection works only when encoder uses a suitable DP configuration,
   * and the configuration and algorithm that is suitable is highly dependent on the use case.
   * If the configuration is not suitable for the use case, it may hurt privacy or utility or both.
   *
   * @hide
   */
  public interface DifferentialPrivacyEncoder {
  
      /**
       * Apply differential privacy to encode a string.
       *
       * @param original An arbitrary string
       * @return Differential privacy encoded bytes derived from the string
       */
      byte[] encodeString(String original);
  
      /**
       * Apply differential privacy to encode a boolean.
       *
       * @param original An arbitrary boolean.
       * @return Differential privacy encoded bytes derived from the boolean
       */
      byte[] encodeBoolean(boolean original);
  
      /**
       * Apply differential privacy to encode sequence of bytes.
       *
       * @param original An arbitrary byte array.
       * @return Differential privacy encoded bytes derived from the bytes
       */
      byte[] encodeBits(byte[] original);
  
      /**
       * Returns the configuration that this encoder is using.
       */
      DifferentialPrivacyConfig getConfig();
  
      /**
       * Return True if the output from encoder is NOT securely randomized, otherwise encoder should
       * be secure to randomize input.
       *
       * <b> A non-secure encoder is intended only for testing only and must not be used to process
       * real data.
       * </b>
       */
      boolean isInsecureEncoderForTest();
  }
  