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      1 /*
      2  * Copyright 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.privacy.internal.longitudinalreporting;
     18 
     19 import android.privacy.DifferentialPrivacyConfig;
     20 import android.privacy.internal.rappor.RapporConfig;
     21 import android.text.TextUtils;
     22 
     23 import com.android.internal.util.Preconditions;
     24 
     25 /**
     26  * A class to store {@link LongitudinalReportingEncoder} configuration.
     27  *
     28  * <ul>
     29  * <li> f is probability to flip input value, used in IRR.
     30  * <li> p is probability to override input value, used in PRR1.
     31  * <li> q is probability to set input value as 1 when result of PRR(p) is true, used in PRR2.
     32  * </ul>
     33  *
     34  * @hide
     35  */
     36 public class LongitudinalReportingConfig implements DifferentialPrivacyConfig {
     37 
     38     private static final String ALGORITHM_NAME = "LongitudinalReporting";
     39 
     40     // Probability to flip input value.
     41     private final double mProbabilityF;
     42 
     43     // Probability to override original value.
     44     private final double mProbabilityP;
     45     // Probability to override value with 1.
     46     private final double mProbabilityQ;
     47 
     48     // IRR config to randomize original value
     49     private final RapporConfig mIRRConfig;
     50 
     51     private final String mEncoderId;
     52 
     53     /**
     54      * Constructor to create {@link LongitudinalReportingConfig} used for {@link
     55      * LongitudinalReportingEncoder}
     56      *
     57      * @param encoderId    Unique encoder id.
     58      * @param probabilityF Probability F used in Longitudinal Reporting algorithm.
     59      * @param probabilityP Probability P used in Longitudinal Reporting algorithm. This will be
     60      *                     quantized to the nearest 1/256.
     61      * @param probabilityQ Probability Q used in Longitudinal Reporting algorithm. This will be
     62      *                     quantized to the nearest 1/256.
     63      */
     64     public LongitudinalReportingConfig(String encoderId, double probabilityF,
     65             double probabilityP, double probabilityQ) {
     66         Preconditions.checkArgument(probabilityF >= 0 && probabilityF <= 1,
     67                 "probabilityF must be in range [0.0, 1.0]");
     68         this.mProbabilityF = probabilityF;
     69         Preconditions.checkArgument(probabilityP >= 0 && probabilityP <= 1,
     70                 "probabilityP must be in range [0.0, 1.0]");
     71         this.mProbabilityP = probabilityP;
     72         Preconditions.checkArgument(probabilityQ >= 0 && probabilityQ <= 1,
     73                 "probabilityQ must be in range [0.0, 1.0]");
     74         this.mProbabilityQ = probabilityQ;
     75         Preconditions.checkArgument(!TextUtils.isEmpty(encoderId), "encoderId cannot be empty");
     76         mEncoderId = encoderId;
     77         mIRRConfig = new RapporConfig(encoderId, 1, 0.0, probabilityF, 1 - probabilityF, 1, 1);
     78     }
     79 
     80     @Override
     81     public String getAlgorithm() {
     82         return ALGORITHM_NAME;
     83     }
     84 
     85     RapporConfig getIRRConfig() {
     86         return mIRRConfig;
     87     }
     88 
     89     double getProbabilityP() {
     90         return mProbabilityP;
     91     }
     92 
     93     double getProbabilityQ() {
     94         return mProbabilityQ;
     95     }
     96 
     97     String getEncoderId() {
     98         return mEncoderId;
     99     }
    100 
    101     @Override
    102     public String toString() {
    103         return String.format("EncoderId: %s, ProbabilityF: %.3f, ProbabilityP: %.3f"
    104                         + ", ProbabilityQ: %.3f",
    105                 mEncoderId, mProbabilityF, mProbabilityP, mProbabilityQ);
    106     }
    107 }
    108