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Commit b70d84a6 authored by Ricky Wai's avatar Ricky Wai
Browse files

Use sha256 of a string as seed in RapporEncoder.insecureEncoder 

Test: atest android.privacy.LongitudinalReportingEncoderTest
Test: atest android.privacy.RapporEncoderTest
Test: atest android.server.net.watchlist.PrivacyUtilsTests

Bug: 76001602
Change-Id: I42d569f34d29125e7adf898b9553053a42149bd4
parent 90ad1540

core/java/android/privacy/internal/rappor/RapporEncoder.java

+16 −1
Original line number Diff line number Diff line
@@ -20,6 +20,10 @@ import android.privacy.DifferentialPrivacyEncoder; 


import com.google.android.rappor.Encoder;



import java.nio.ByteBuffer;

import java.nio.charset.StandardCharsets;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import java.util.Random;
@@ -66,7 +70,7 @@ public class RapporEncoder implements DifferentialPrivacyEncoder { 
            random = sSecureRandom;

        } else {

            // To have deterministic result by hard coding encoder id as seed.

            random = new Random((long) config.mEncoderId.hashCode());

            random = new Random(getInsecureSeed(config.mEncoderId));

            userSecret = INSECURE_SECRET;

        }

        mEncoder = new Encoder(random, null, null,
@@ -75,6 +79,17 @@ public class RapporEncoder implements DifferentialPrivacyEncoder { 
                config.mNumCohorts, config.mNumBloomHashes);

    }



    private long getInsecureSeed(String input) {

        try {

            MessageDigest digest = MessageDigest.getInstance("SHA-256");

            byte[] bytes = digest.digest(input.getBytes(StandardCharsets.UTF_8));

            return ByteBuffer.wrap(bytes).getLong();

        } catch (NoSuchAlgorithmException e) {

            // Should not happen

            throw new AssertionError("Unable generate insecure seed");

        }

    }



    /**

     * Create {@link RapporEncoder} with {@link RapporConfig} and user secret provided.

     *

core/tests/privacytests/Android.mk

+1 −1
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ LOCAL_MODULE_TAGS := tests 
LOCAL_SRC_FILES := \

    $(call all-java-files-under, src)



LOCAL_STATIC_JAVA_LIBRARIES := junit rappor-tests android-support-test

LOCAL_STATIC_JAVA_LIBRARIES := junit rappor-tests android-support-test truth-prebuilt



LOCAL_JAVA_LIBRARIES := android.test.runner

LOCAL_PACKAGE_NAME := FrameworksPrivacyLibraryTests

core/tests/privacytests/src/android/privacy/LongitudinalReportingEncoderTest.java

+37 −11
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 


package android.privacy;



import static com.google.common.truth.Truth.assertThat;

import static org.junit.Assert.assertEquals;

import static org.junit.Assert.assertFalse;

import static org.junit.Assert.assertTrue;
@@ -72,27 +73,27 @@ public class LongitudinalReportingEncoderTest { 
        final LongitudinalReportingEncoder encoder =

                LongitudinalReportingEncoder.createInsecureEncoderForTest(

                        config);

        assertEquals(0, encoder.encodeBoolean(true)[0]);

        assertEquals(0, encoder.encodeBoolean(true)[0]);

        assertEquals(1, encoder.encodeBoolean(true)[0]);

        assertEquals(0, encoder.encodeBoolean(true)[0]);

        assertEquals(1, encoder.encodeBoolean(true)[0]);

        assertEquals(1, encoder.encodeBoolean(true)[0]);

        assertEquals(0, encoder.encodeBoolean(true)[0]);

        assertEquals(1, encoder.encodeBoolean(true)[0]);

        assertEquals(1, encoder.encodeBoolean(true)[0]);

        assertEquals(1, encoder.encodeBoolean(true)[0]);

        assertEquals(1, encoder.encodeBoolean(true)[0]);

        assertEquals(0, encoder.encodeBoolean(true)[0]);

        assertEquals(0, encoder.encodeBoolean(true)[0]);



        assertEquals(0, encoder.encodeBoolean(false)[0]);

        assertEquals(1, encoder.encodeBoolean(false)[0]);

        assertEquals(1, encoder.encodeBoolean(false)[0]);

        assertEquals(1, encoder.encodeBoolean(false)[0]);

        assertEquals(0, encoder.encodeBoolean(false)[0]);

        assertEquals(0, encoder.encodeBoolean(false)[0]);

        assertEquals(1, encoder.encodeBoolean(false)[0]);

        assertEquals(0, encoder.encodeBoolean(false)[0]);

        assertEquals(1, encoder.encodeBoolean(false)[0]);

        assertEquals(1, encoder.encodeBoolean(false)[0]);

        assertEquals(0, encoder.encodeBoolean(false)[0]);

        assertEquals(0, encoder.encodeBoolean(false)[0]);

        assertEquals(0, encoder.encodeBoolean(false)[0]);

        assertEquals(0, encoder.encodeBoolean(false)[0]);



        // Test if IRR returns original result when f = 0

        final LongitudinalReportingConfig config2 = new LongitudinalReportingConfig(
@@ -127,6 +128,31 @@ public class LongitudinalReportingEncoderTest { 
        }

    }



    @Test

    public void testLongitudinalReportingInsecureEncoder_setSeedCorrectly() throws Exception {

        final int n = 10000;

        final double f = 0.35;

        final double expectedTrueSum = n * f;

        final double valueRange = 5 * Math.sqrt(n * f * (1 - f));

        int trueSum = 0;

        for (int i = 0; i < n; i++) {

            final LongitudinalReportingConfig config = new LongitudinalReportingConfig(

                    "encoder" + i,  // encoderId

                    f,  // probabilityF

                    0,  // probabilityP

                    1);  // probabilityQ

            final LongitudinalReportingEncoder encoder

                    = LongitudinalReportingEncoder.createInsecureEncoderForTest(config);

            boolean encodedFalse = encoder.encodeBoolean(false)[0] > 0;

            if (encodedFalse) {

                trueSum += 1;

            }

        }

        // Total number of true(s) should be around the mean (10000 * 0.35)

        assertThat((double) trueSum).isLessThan(expectedTrueSum + valueRange);

        assertThat((double) trueSum).isAtLeast(expectedTrueSum - valueRange);

    }



    @Test

    public void testLongitudinalReportingEncoder_basicPRRTest() throws Exception {

        // Should always return original value when p = 0
@@ -290,8 +316,8 @@ public class LongitudinalReportingEncoderTest { 
            }

        }

        // Total number of true(s) should be around the mean (1000 * 0.8)

        assertTrue(trueSum1 < expectedTrueSum1 + valueRange1);

        assertTrue(trueSum1 > expectedTrueSum1 - valueRange1);

        assertThat((double) trueSum1).isLessThan(expectedTrueSum1 + valueRange1);

        assertThat((double) trueSum1).isAtLeast(expectedTrueSum1 - valueRange1);



        // Confirm if PRR randomizer is working correctly

        final int n2 = 1000;
@@ -314,8 +340,8 @@ public class LongitudinalReportingEncoderTest { 
            }

        }

        // Total number of true(s) should be around the mean (1000 * 0.2)

        assertTrue(trueSum2 < expectedTrueSum2 + valueRange2);

        assertTrue(trueSum2 > expectedTrueSum2 - valueRange2);

        assertThat((double) trueSum2).isLessThan(expectedTrueSum2 + valueRange2);

        assertThat((double) trueSum2).isAtLeast(expectedTrueSum2 - valueRange2);

    }



    @Test

core/tests/privacytests/src/android/privacy/RapporEncoderTest.java

+9 −8
Original line number Diff line number Diff line
@@ -79,11 +79,11 @@ public class RapporEncoderTest { 
    public void testRapporEncoder_IRRWithPRR() throws Exception {

        int numBits = 8;

        final long inputValue = 254L;

        final long prrValue = 250L;

        final long prrAndIrrValue = 244L;

        final long expectedPrrValue = 126L;

        final long expectedPrrAndIrrValue = 79L;



        final RapporConfig config1 = new RapporConfig(

                "Foo", // encoderId

                "Foo2", // encoderId

                numBits, // numBits,

                0.25, // probabilityF

                0, // probabilityP
@@ -93,12 +93,12 @@ public class RapporEncoderTest { 
        // Use insecure encoder here as we want to get the exact output.

        final RapporEncoder encoder1 = RapporEncoder.createInsecureEncoderForTest(config1);

        // Verify that PRR is working as expected.

        assertEquals(prrValue, toLong(encoder1.encodeBits(toBytes(inputValue))));

        assertEquals(expectedPrrValue, toLong(encoder1.encodeBits(toBytes(inputValue))));

        assertTrue(encoder1.isInsecureEncoderForTest());



        // Verify that IRR is working as expected.

        final RapporConfig config2 = new RapporConfig(

                "Foo", // encoderId

                "Foo2", // encoderId

                numBits, // numBits,

                0, // probabilityF

                0.3, // probabilityP
@@ -107,11 +107,12 @@ public class RapporEncoderTest { 
                2); // numBloomHashes

        // Use insecure encoder here as we want to get the exact output.

        final RapporEncoder encoder2 = RapporEncoder.createInsecureEncoderForTest(config2);

        assertEquals(prrAndIrrValue, toLong(encoder2.encodeBits(toBytes(prrValue))));

        assertEquals(expectedPrrAndIrrValue,

                toLong(encoder2.encodeBits(toBytes(expectedPrrValue))));



        // Test that end-to-end is the result of PRR + IRR.

        final RapporConfig config3 = new RapporConfig(

                "Foo", // encoderId

                "Foo2", // encoderId

                numBits, // numBits,

                0.25, // probabilityF

                0.3, // probabilityP
@@ -120,7 +121,7 @@ public class RapporEncoderTest { 
                2); // numBloomHashes

        final RapporEncoder encoder3 = RapporEncoder.createInsecureEncoderForTest(config3);

        // Verify that PRR is working as expected.

        assertEquals(prrAndIrrValue, toLong(encoder3.encodeBits(toBytes(inputValue))));

        assertEquals(expectedPrrAndIrrValue, toLong(encoder3.encodeBits(toBytes(inputValue))));

    }



    @Test

services/tests/servicestests/src/com/android/server/net/watchlist/PrivacyUtilsTests.java

+3 −3
Original line number Diff line number Diff line
@@ -75,11 +75,11 @@ public class PrivacyUtilsTests { 
        Map<String, Boolean> result = PrivacyUtils.createDpEncodedReportMap(false, null,

                TEST_DIGEST_LIST, TEST_AGGREGATED_RESULT1);

        assertEquals(6, result.size());

        assertTrue(result.get("C86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB48"));

        assertFalse(result.get("C86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB48"));

        assertTrue(result.get("C86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB49"));

        assertTrue(result.get("C86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB47"));

        assertFalse(result.get("E86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB45"));

        assertTrue(result.get("C86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB44"));

        assertTrue(result.get("E86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB45"));

        assertFalse(result.get("C86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB44"));

        assertTrue(result.get("B86F9D37425340B635F43D6BC2506630761ADA71F5E6BBDBCA4651C479F9FB43"));

    }