Add a low-frequency RAPPOR configuration, and use it for Safe Browsing and Permissions metrics.

components/rappor/rappor_parameters.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_RAPPOR_RAPPOR_PARAMETERS_H_
 #define COMPONENTS_RAPPOR_RAPPOR_PARAMETERS_H_
 
 #include <string>
 
 namespace rappor {
 
 // Levels of noise added to a sample.
 enum NoiseLevel {
   NO_NOISE = 0,
   NORMAL_NOISE,
+  SPARSE_NOISE,
   NUM_NOISE_LEVELS,
 };
 
 // The type of data stored in a metric.
+// Any use of the LOW_FREQUENCY types must be approved by Chrome Privacy and
+// the rappor-dev team.
 enum RapporType {
   // Generic metrics from UMA opt-in users.
   UMA_RAPPOR_TYPE = 0,
-  // Generic metrics for SafeBrowsing users.
+  // Generic metrics for SafeBrowsing users. Deprecated, replaced by
+  // LOW_FREQUENCY_SAFEBROWSING_RAPPOR_TYPE.
   SAFEBROWSING_RAPPOR_TYPE,
   // Deprecated: Use UMA_RAPPOR_TYPE for new metrics
   ETLD_PLUS_ONE_RAPPOR_TYPE,
+  // Type for low-frequency metrics from UMA opt-in users.
+  LOW_FREQUENCY_UMA_RAPPOR_TYPE,
+  // Type for low-frequency metrics from SafeBrowsing users.
+  LOW_FREQUENCY_SAFEBROWSING_RAPPOR_TYPE,
+  // Type for low-frequency metrics from UMA opt-in users. Do not use for new
+  // metrics.
+  LOW_FREQUENCY_ETLD_PLUS_ONE_RAPPOR_TYPE,
   NUM_RAPPOR_TYPES,
   COARSE_RAPPOR_TYPE = SAFEBROWSING_RAPPOR_TYPE,
 };
 
 enum Probability {
   PROBABILITY_100,   // 100%
   PROBABILITY_75,    // 75%
   PROBABILITY_50,    // 50%
   PROBABILITY_25,    // 25%
   PROBABILITY_0,     // 0%
 };
 
 
 // A metric is reported when its reporting group is in the set of groups
 // passed in to RapporService::Start()
 enum RecordingGroup {
   // Metrics for UMA users.
   UMA_RAPPOR_GROUP = 1 << 0,
   // Metrics related to SafeBrowsing, for SafeBrowsing users.
   SAFEBROWSING_RAPPOR_GROUP = 1 << 1,
 };
 
 
 // An object describing noise probabilities for a noise level
 struct NoiseParameters {
-  // The probability that a bit will be redacted with fake data.
+  // The probability that a bit will be redacted with fake data. This
+  // corresponds to the F privacy parameter.
   Probability fake_prob;
   // The probability that a fake bit will be a one.
   Probability fake_one_prob;
-  // The probability that a one bit in the redacted data reports as one.
+  // The probability that a one bit in the redacted data reports as one. This
+  // corresponds to the Q privacy parameter
   Probability one_coin_prob;
-  // The probability that a zero bit in the redacted data reports as one.
+  // The probability that a zero bit in the redacted data reports as one. This
+  // corresponds to the P privacy parameter.
   Probability zero_coin_prob;
 };
 
 // An object describing a rappor metric and the parameters used to generate it.
 //
 // For a full description of the rappor metrics, see
 // http://www.chromium.org/developers/design-documents/rappor
 struct RapporParameters {
   // Get a string representing the parameters, for DCHECK_EQ.
   std::string ToString() const;
@@ skipping 28 matching lines @@
      rappor::PROBABILITY_100 /* One coin probability */,
      rappor::PROBABILITY_0 /* Zero coin probability */,
     },
     // NORMAL_NOISE
     {
      rappor::PROBABILITY_50 /* Fake data probability */,
      rappor::PROBABILITY_50 /* Fake one probability */,
      rappor::PROBABILITY_75 /* One coin probability */,
      rappor::PROBABILITY_25 /* Zero coin probability */,
     },
+    // SPARSE_NOISE
+    {
+     rappor::PROBABILITY_25 /* Fake data probability */,
+     rappor::PROBABILITY_50 /* Fake one probability */,
+     rappor::PROBABILITY_75 /* One coin probability */,
+     rappor::PROBABILITY_25 /* Zero coin probability */,
+    },
 };
 
 const RapporParameters kRapporParametersForType[NUM_RAPPOR_TYPES] = {
     // UMA_RAPPOR_TYPE
     {128 /* Num cohorts */,
      4 /* Bloom filter size bytes */,
      2 /* Bloom filter hash count */,
      rappor::NORMAL_NOISE /* Noise level */,
      UMA_RAPPOR_GROUP /* Recording group */},
     // SAFEBROWSING_RAPPOR_TYPE
     {128 /* Num cohorts */,
      1 /* Bloom filter size bytes */,
      2 /* Bloom filter hash count */,
      rappor::NORMAL_NOISE /* Noise level */,
      SAFEBROWSING_RAPPOR_GROUP /* Recording group */},
     // ETLD_PLUS_ONE_RAPPOR_TYPE
     {128 /* Num cohorts */,
      16 /* Bloom filter size bytes */,
      2 /* Bloom filter hash count */,
      rappor::NORMAL_NOISE /* Noise level */,
      UMA_RAPPOR_GROUP /* Recording group */},
+    // LOW_FREQUENCY_UMA_RAPPOR_TYPE
+    {128 /* Num cohorts */,
+     4 /* Bloom filter size bytes */,
+     2 /* Bloom filter hash count */,
+     rappor::SPARSE_NOISE /* Noise level */,
+     UMA_RAPPOR_GROUP /* Recording group */},
+    // LOW_FREQUENCY_SAFEBROWSING_RAPPOR_TYPE
+    {128 /* Num cohorts */,
+     1 /* Bloom filter size bytes */,
+     2 /* Bloom filter hash count */,
+     rappor::SPARSE_NOISE /* Noise level */,
+     SAFEBROWSING_RAPPOR_GROUP /* Recording group */},
+    // LOW_FREQUENCY_ETLD_PLUS_ONE_RAPPOR_TYPE
+    {128 /* Num cohorts */,
+     16 /* Bloom filter size bytes */,
+     2 /* Bloom filter hash count */,
+     rappor::SPARSE_NOISE /* Noise level */,
+     UMA_RAPPOR_GROUP /* Recording group */},
 };
 
 }  // namespace internal
 
 }  // namespace rappor
 
 #endif  // COMPONENTS_RAPPOR_RAPPOR_PARAMETERS_H_